How to use the Olympus Gradation Function?

 Last Update:- 12th June 2023

1. Introduction

The computational features from Olympus are well regarded by those who use them. Unfortunately, many Olympus photographers will never experience the benefits of computational photography or the broader application of functions like High-Resolution Imaging and the Gradation function. The main reason is cleverly designed counter-marketing filters.

It doesn't need much to see the Engineering Team at the old Olympus Imaging Business was at least 10 years ahead of its competitors. The EM-5 MKI is a 2nd generation mirrorless camera with a 5-Axis IBIS solution for both stills and video. Canon and Nikon designed and sold DSLRs like the 60D, 5D3, D800, and D5200 when Olympus introduced the EM-5 with more Creative Color features.

Olympus EP-7 with the 45mm f1.8 lens, Gradation = "Auto." These Enhanced Raw Files were converted and edited in Workspace.

We reviewed the importance of SNR and sensor saturation. For example, how do we get more light onto the image sensor? Should we increase the ISO, use a flash, or adjust the Aperture/Shutter? We discussed ISO amplification and the role of the Aperture and Shutter. We will use this information to learn more about Olympus cameras and the Gradation function.

TIP: View the images on a large screen and study the descriptions...

EM1 III with the 12 - 45mm f4.0 Pro lens - ISO200, f5.6, 1/1.16Sec, +0.7EV - The focus stacked OOC image was edited in Workspace.

My lovely wife bought flowers, and I created a small studio for my EM1 III, tripod, large diffuser, and Rotolight Neo 2. Did you know the Gradation function changes your exposure values? Experiment with the 4 Gradation options and watch your camera's auto-exposure values change. 

A focus-stacked ISO3200 example. I used 4 (bracketed) Enhanced Raw Files and applied the AI noise filter before stacking them in Workspace.

I will discuss the following:

1. Introduction
2. Why is the Gradation High option interesting for ETTR?
3. The three reasons why photographers use ETTR in 2023
4. Practical discussion on using ETTR with Olympus cameras
5. A brief overview of noise and the Olympus Noise Filter...
6. Conclusion (See my thoughts about the EM1 III and XT-5)

The Pen F and 17mm f1.8 lens (Edited version). I selected Gradation High in my Pen F and Normal to "color grade" the Enhanced Raw File.

2. Why is the Gradation HIGH option interesting for ETTR?

The Gradation function has 4 tone curves (Normal, Auto, Low, and High). The EM1 III U/M says it makes tiny adjustments to the camera's tones. See the user's manual for a description of each.

I have been using the Gradation function more frequently over the past year. For example, the Auto option is used to edit the image (raw + jpeg) with the camera or Workspace. I also use the Highlights & Shadows sliders to fine-tune the camera's Tone Curve. It's possible to simulate these "camera" settings in Workspace? In a previous article, I said the Gradation function should be great for ETTR. This article explores the Gradation High option for ETTR.

I often experience the WOW factor as I learn more about the Computational Features from Olympus. We can compare the Gradation "High" option with a V-Log profile and "Normal" to Color Grading. I tested this on my EM1 III with the Gradation "High" option and "color grading" via the Enhanced Raw File and Workspace. It's now possible to use ETTR without much effort.

Why do I use Midtones to adjust the final brightness of my image? Because it preserves my Neutral Gray values. Neutral (18%) gray mean the camera's colors are accurate. The exposure compensation slider adjusts the camera's Neutral Gray values. (Ref. the Zone System) This is why it's good to use the exposure and mid-tone adjustments separately. Does this also apply to ETTR? Yes, it's best to correct any ETTR over-exposures with the exposure compensation slider...

Did Olympus improve the Gradation function (Tone Curves) over the years? They said they did in the EM-5 launch documents. I didn't verify the more recent cameras...

The unedited OOC jpeg version of the above image with Gradation set to High. I used the Gradation function for ETTR.

3. The three reasons for using ETTR in 2023

Here are the 3 main reasons for using ETTR:-

1. Cameras do not saturate the sensor in Auto Exposure mode
1. The reason is a built-in DR safety margin for Auto users...
2. These safety margins impact your shadow details & noise
3. ETTR enables photographers to saturate the image sensor
4. How did I learn this? Knowledge and an unfiltered mindset
2. ETTR helps us to improve the sensor's Signal to Noise ratio (SNR)
1. The visibility of the sensor's noise floor increases at lower SNRs
2. Upping the SNR means the sensor's noise floor becomes less visible
3. ETTR is especially effective in the shadow areas of the image
3. ETTR improves our tonal data in the shadow areas of the image
1. Sensors are linear devices with less tonal data in the shadows
2. ETTR shifts the tone curves to the right to record more data

See this article about exposure, gamma curves, and tonal data...

4. Practical discussion on ETTR and Olympus

The Gradation function is one of the several computational functions from Olympus and a powerful option for ETTR. The HIGH option automatically saturates the sensor without clipping the highlights (EM5 Press Release). That means Workspace, the Enhanced Raw Format, and the Gradation High option let us increase the SNR, saturate the sensor, and shift the camera's tone curve to the right. We reset (color grade) the HIGH option with the Gradation NORMAL option in Workspace. 

The resulting 16-Bit Tiff file from Workspace has a higher SNR, more tonal data, looks like a regular image, and offers more flexibility when we edit the converted 16-bit Tiff file in Photoshop.

Here are a few practical Tips:

• Our goal is more light on the sensor (camera settings, time of day, and flash)
• It's critical to be clear about the ISO's role versus the Aperture/Shutter Speed.
• Use a fixed ISO value to prevent the camera from amplifying the image signal
• Never disregard the importance of using a flash to add more light to the sensor
• It's always good to set your White Balance manually. (Not critical for ETTR)
• It helps to create a flat profile with Highlights/Shadows for Gradation High...
• Experiment with your Histogram Settings and use the Histogram with ETTR.

Olympus Pen F with 45mm f1.8 lens - ISO1600, f7.1, 1/8 Sec - Converted and "color graded" in Workspace, no noise reduction.

Experiment with the Gradation High and Highlight/Shadows functions to create your "ETTR" camera profiles. A flat Tone Curve means negative values for Highlights and positive for Shadows, like Highlights -3 and Shadows +4. Always use the same principle of creating a Tone Curve in the camera and "Color Grading" (resetting) in Workspace and the Enhanced Raw File. "Color grading" Olympus Tone Curves do not mean opposite values like we typically do with V-Log Profiles. It simply means returning the camera's settings to their default values. The Enhanced Raw File allows us to reset the image to Neutral Gray in Workspace.

Raw Converters use a fixed Gamma curve (profile) to enable us to view the data. The older software Viewer 3, had a Gamma setting to change the profile's shadows, midrange, and highlights. Consider the Gradation and Highlights/Shadow adjustments as "Pre-Gamma" or Tone Curve adjustments in the camera. It's possible to Color-Grade or use them as Pre-Gamma adjustments.

The Gradation and highlight/shadow functions let us create flat tone curves or edit the image look. Always ask yourself, how can I get more light on my sensor, and what should my final image (jpeg) look like? This is why we use the aperture/shutter or exposure compensation to adjust the exposure (light) and the mid-tone function to adjust the look of the image with Workspace or the camera? The Enhanced Raw Format allows us to access almost any camera setting in Workspace.

The Olympus FL300R needs almost no space.

Does Color Grading change any of the ETTR benefits? No, the recording happens in the camera, and the ETTR benefits are part of the final image. Workspace does not add or remove any light from the sensor. That's why it's only possible to simulate the ETTR function in Workspace. 

"Color Grading" means the camera values are zero in Workspace. That means we will change the camera settings, Shadows +5 and Highlight -5 (flat tone curve), to zero in Workspace. Experiment by applying "ETTR" with the camera and Color-Grading the Tone Curve in Workspace. Take the time to practice using your camera's Exposure Meter and the feedback from the Histogram.

Did the noise disappear in the above illustration? No, the size of the sensor's noise floor stays the same. We only improved the SNR, which means the noise floor became less visible. Should reviewers say smaller sensors have more noise? Absolutely not... ALL sensors have a noise floor...

The Olympus XZ-2 is a great compact camera. I prefer to get my info from manufacturers and don't trust camera reviewers or photography forum experts. My research and knowledge of digital cameras are also a great help. Discovering the XZ-2 and the satisfaction of using great oldies like the XZ-1 and the XZ-2 is exhilarating. The XZ-2 uses a BSI sensor, and the XZ-1 a CCD sensor.

Olympus Stylus XZ-2 - ISO100, f4.0, 1/500 - The Gradation Auto option in the camera and color-graded in Workspace.

The EP-3 is another oldie and an excellent camera. I took my EP-3 with my 12-50mm lens for a late afternoon walk with the dog. The XZ-2 and the EP-3 are compatible with the VF-4 Electronic View Finder. My XZ-2 was set to Auto Gradation in the above image.

I typically use 2-steps to convert and edit my Enhanced Raw Files. I select and edit my camera settings in Workspace for step 1, and the focus is specific or advanced image editing in step 2. Advanced editing can be done in Workspace or something like Photoshop. For example, I used the Gradation Auto option, Highlights/Shadows, and Tone Curves to edit the image below. We only need Step 1 or the converted 16-Bit Tiff file to post-process the image in Photoshop.

The EP-3 and the 12-50mm lens - ISO3200, f5.2, 1/80 - I converted the Enhanced Raw File with WS (Noise Filter = Low) and tweaked it in Photoshop.

The EP3 raw file was converted with PhotoLab 5, and I used DeepPrime (AI Noise Filter). The final image was edited with Photoshop.

5. A brief overview of image noise and the Olympus Noise Filter

Olympus photographers should experiment more with the Olympus Noise Filter. The main reason newer camera models have less noise is a smaller noise floor in modern sensors, more sensitive sensors, and more processing power like the Pen EP-3 and EM1 III. DxO PhotoLab became my benchmark to rate the Noise Filter in Olympus cameras and Workspace. The PhotoLab "Prime" option is enough for my general photography needs with the PEN, OMD, and XZ-2. I only use DeepPrime for extreme cases. It's possible to cancel the Olympus Noise Filter in favor of the PhotoLab noise filter...

Olympus cameras and Workspace use excellent Noise Filters. The Workspace AI option is enough for any challenging situation with the EM1 II/III or the OM-1. The default Olympus Noise Filter setting is "Normal." I prefer the "Low" option for my Olympus cameras. One can always use the Enhanced Raw Format to select the Standard or High options in Workspace. I rarely use the additional two sliders in the Workspace. Study this article for more on image noise and image sensors.

I used the Gradation "Auto" and Noise Filter "Low" options in the image below. I was surprised by the excellent DR and IQ of my Pen EP-3 and the XZ-2. The Pen EP-3 is a surprisingly good camera with all the marketing filters removed. For example, always start with the Official News Releases from Olympus if you like to learn more about Olympus cameras. See the Stylus XZ-2 News Release.

The reason for the little shadow noise (image below) must be a small noise floor in the XZ-2, plus the SNR was high at ISO100. Shadow Noise, or the visibility of the noise floor, increases at ISO800. The size of the sensor is irrelevant when I use my camera. I am only thinking about the available light at the sensor, any Tone Curves I like to use, and optimizing the SNR of my image signal...

Olympus XZ-2 - ISO100, f4.0, 1/400 - ND filter ON.

6. Conclusion

Marketers mislead photographers with statements like "Workspace is just another raw converter." Why shouldn't we compare Workspace, Lightroom, ON1, and Capture One to Workspace? Because these Raw Converters cannot simulate your Olympus camera settings. It's not the first time Marketers used false information to distract photographers. Micro Four Third cameras are some of the most filtered products in 2023. How many photographers are familiar with the Color and Creative Strategy from Olympus and how Olympus showcased it with the E30, EM5 MKII, and Pen F?

Folks, we don't need ETTR for good results with M43 cameras. Knowledge gives us an overview of photography. Knowledge empowers photographers to improve their image quality, and knowledge is a light casting different perspectives on the misleading filters from marketers...

I am working on an article for the EM1 III and the Fuji XT-5. Do we compare only IQ, or should we do more? For example, while focus-stacking with my EM1 III, I tried computational ETTR techniques plus processing an 80MP High-Ressolution image in the camera. 

Considering this unique level of computational flexibility from my Olympus EM1 III, Workspace, and the Enhanced Raw Format, how should I plan a balanced and factual comparison between the EM1 III and something like the Fuji XT-5? Both these cameras are good but also radically different...

For more on Creative Color and Computational Photography, see this article.

Take care and God's Bless

Best

Siegfried

A few casual images while walking the dog...

The images below are from my Pen EP-3 and the 75mm f1.8 lens. I didn't do anything special for my camera settings. The images benefited from converting the Enhanced Raw Files in Workspace. I used the adjustments below on all the raw files and exported them as 16-bit Tiff files to Photoshop.

Older 12MP sensors have more noise (large noise floor) than newer M43 sensors. The skies were known for visible noise from these older cameras. The Noise Filter "Low" option was enough to clean the skies without losing details. It helps to manage older sensors with the SNR-to-ISO ratio.

These are my final post-processing steps in Photoshop:-

• I cropped the image for Instagram (4:5 ratio)
• I added a little contrast with Curves in Photoshop
• I sharpened with the High Pass Filter (setting = 1.6)
• Using a "Soft Light" blending mode on a duplicated layer

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/800.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/200.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/800.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/1000.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/500.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/160.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/640.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/160.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f14, 1/80.

Olympus EP-3 and 75mm f1.8 lens - ISO200, f5.6, 1/400 (Action shot).

The 7 points each Digital Photographer should know

Last updated:- 3rd August 2023

Introduction.

This article reviews 7 technical points each digital photographer should know. They also explain why photographers are the creative power behind photography. These technical points can be regarded as "enablers" to improve your Image Quality. The fun or creative part of photography also improves with these 7 points. Knowledge is an integral part of our journey with digital cameras...

Olympus E400 with 25mm f2.8 lens - ISO100, f7.1, 1/160 - It's a 10MP, 4-Thirds CCD sensor. It's the OOC jpeg.

Technical and theoretical information is part of a general process of improving our camera skills. It explains how to improve our exposure skills (SNR to ISO ratio) and our ability to visualize the sensor's Saturation (performance) and SNR (noise) levels. Knowledge is always critical...

Technical information also helps us explain why Olympus used a 20MP sensor for the OM-1...

There's only one right way to discuss and study digital cameras.

Many photographers prefer a more simplified technical conversation. I listed 7 points to assist people in this learning process. It highlights only the most critical points photographers should know.

These 7 points are:

1. The exposure triangle works for analog & digital cameras.
2. Know the image signal path from the subject to the SD card.
3. How to manage the sensor's performance and the SNR ratio.
4. The 7 steps manufacturers use to manage the image sensor.
5. The basic types of noise and how to control image noise.
6. Various kinds of CMOS sensors and why the differences.
7. A basic illustration that summarizes all digital cameras.

These 3 points are also critical when we evaluate different cameras:

1. Optical differences - Always consider the differences between formats
2. Technical similarities - This article focuses on the technical similarities
3. Editing Software - We shouldn't ignore the importance of image editing

Why is the Olympus X-Z2 such an interesting digital camera in 2023?

Why do we benefit from technical discussions? Knowledge is the enabler every photographer needs to master his or her digital camera. Knowledge empowers us to manage the sensor's performance and not simply rely on size. Pixels capture Photons and not the size of the sensor's backplate. For example, did you know the Effective Pixel Area is more important than the size of the sensor? Each pixel's control wiring reduces the light-sensitive area of the pixel. This means standard CMOS sensors have a smaller Effective Pixel Area (67%) than LiveMOS (85%) or BSI CMOS (97%) sensors.

Consider the following 10 points when evaluating your next camera:

1. The focus should be on pixels because pixels capture photons
2. Fewer pixels mean a smaller noise floor and better efficiency
3. The type of sensor influences the sensor's effective pixel area
4. More resolution means smaller pixels with smaller pixel areas
5. Pixel area changes the Optical Efficiency & sensor sensitivity
6. More pixels means more pixel control wiring with more noise
7. MZuiko Standard & Premium lenses are SMALL and excellent
8. Each sensor size has different & unique optical characteristics
9. The size of the sensor does not change its technical limitations
10. Stacked BSI sensors are known for fast sensor readout speeds

1. The Exposure Triangle

Your Aperture and Shutter Speed determine how much light reaches the film strip in analog cameras. Old film cameras have a mechanical ISO (ASA) adjustment. The ISO setting synchronizes the camera's exposure values to the sensitivity rating of the film and is set once for each.

Your Aperture and Shutter Speed are the same for digital cameras. The sensor's final sensitivity is measured and set at the factory. In other words, it's calibrated to deliver a +/-1EV delta for each full-stop ISO adjustment. The sensor's sensitivity doesn't change once it's calibrated. The ISO function has a new role with digital cameras. It now amplifies the sensor's output signal (image brightness). Like analog cameras, your ISO is a critical "exposure" variable in the exposure formula.

The ISO also amplifies the image sensor's noise floor. It's not correct to say the ISO creates noise. All sensors have an active noise floor when the camera is switched on. We can influence the visibility of the sensor's noise floor (image noise) with the SNR to ISO ratio. This means our goal is more reflected light on the image sensor. This increases its saturation level and the image signal's SNR.

Olympus E30 with 14-54mm f2.8-3.5 Pro Lens - ISO100, f7.1, 1/400 - This is the OOC jpeg image

2. The image signal path from the subject to the SD card

Study this link for more information on points 2, 3, 4, and 5. The challenge was to create a basic but theoretically correct model to explain the digital camera. The secret is to exclude any technical data with no practical value. It's easy to discuss and quote useless charts and information.

Familiarize yourself with the following illustration explaining the image signal path...

Promoters like to distract photographers by claiming the A/D converter is part of the pixel. While correct in some unique cases, the basic flow diagram in the above illustration stays the same. One can say much about the technical aspects of the digital camera. The question should always be, will new claims or information improve your photography, or is it useless information?

3. How to manage the performance of your Image Sensor

This illustration summarises how we manage the image sensor plus any visible noise. A more detailed description of managing your sensor's performance is available here, in section 5.

Photographers don't think of exposing the sensor and amplifying the image signal. The aperture and shutter speed "expose" the sensor, and the final exposure (image brightness) is set with the ISO. This concept forms the foundation for improving our image quality with M43 cameras. This is also how we manage the sensor's performance. The goal is to increase the light exposing the sensor. Increasing the reflected light on the sensor means less visible noise and more tonal data.

Assume you have a choice between ISO1250 and ISO1600. Most photographers would select ISO1600 without considering the image signal. That means the sensor received less light at ISO1600. That will reduce the sensor's saturation level and SNR. The resulting images will have less tonal data with more visible image noise. Your digital photography and exposure skills will grow in leaps and bounds as you grasp this simple concept and make it a part of your digital photography.

Olympus E420 with 18 - 180mm lens - ISO100, f6.3, 1/320 - The Enhanced Raw File was edited in Workspace.

Why should we edit our images to the correct exposures? Study the exposure formula here. Always use neutral gray (18%) exposure and WB values. This ensures accurate image colors. This also means resetting your ETTR or SNR-to-ISO ratio to neutral gray in Workspace. Study this article on how to reset your camera adjustments. Always do your editing with 18% gray brightness levels. That's why you should include Workspace and the Enhanced RAW Format in your image-taking process.

4. The 7 steps manufacturers use to improve image sensors

The following illustration describes the 7 questions manufacturers ask when designing new cameras. For example, one critical aspect of selecting the appropriate sensor is Sensor Readout Speed. This impacts the camera's Silent Shutter or Rolling Shutter efficiency. Standard CMOS sensors are known for having slower readout speeds. Stacked BSI sensors solved this problem with higher sensor readout speeds. Stacked configurations are unique to Stacked BSI "CMOS type" sensors.

Study the illustration below...

5. The basic types of noise and how we control image noise

I always wish someone would ask the question when I see statements like smaller sensors have more noise. What question? The question is simply, where does image noise come from..?

Study the link in section 2 for an overview of the illustration below. Each digital photographer should master the Photons to Electrons graph in this illustration. The most important thing to learn from this illustration is sensors perform at their best when fully saturated. Our goal should always be more reflected light to saturate the sensor at any ISO. This technique is better known as ETTR. The Shutter Speed and Aperture control the light exposing the sensor. The histogram shows what's happening with the sensor at fixed ISOs.

Study these points explaining the graph:-

• The camera's aperture and shutter speed controls the light reaching the sensor.
• The sensor is fully saturated at the native ISO, and the exposure is at point B.
• A fully saturated sensor means we have the highest signal-to-noise ratio (SNR).
• Cameras have a safety buffer in Auto Mode. They will not expose up to point B.
• This safety buffer results in a lower SNR and the histogram moving to the left.
• ETTR means we control the exposure. The goal is to saturate the image sensor.
• Study and understand the noise floor. Fewer photons (light) means a lower SNR.
• The graph is linear, meaning the bulk of the Tonal Data is in the mids and highs.
• The graph plus the noise summary are powerful tools for studying image sensors.
• Spend time with this illustration. It's one of the most powerful photography tools.  

Olympus E450 with the 14-42mm kit lens - ISO100, f7.1, 1/320 - My wife took this OOC jpeg image.

ETTR is a technique we use to control the sensor's SNR to ISO ratio. We can also describe this as managing the sensor's performance or saturation level. Why do we need the highest possible SNR? A fully saturated image sensor gives us the highest SNR with the least amount of visible image noise. Higher ISO values mean less light on the sensor and lower SNR values. This is why it's critical to carefully select negative exposure compensations or higher ISOs. Use the photons to electrons graph to set the best SNR to ISO ratio for your application and sensor in your camera.

It's critical to familiarize yourself with the information in this article. Don't walk away because others do. It takes practice to appreciate the benefits of the above illustration. I continue to learn new techniques with this powerful tool. These exposure techniques are especially effective with older cameras with low-sensitivity image sensors. Implementing this knowledge is as simple as the example in section 2. You will discover more solutions as you practice.

6. The various kinds of CMOS image sensors

Photographers should know the different types of CMOS sensors in digital cameras. This will help them evaluate and select the best camera for the job...

7. A basic illustration to summarize all image sensors

I always considered this absolute focus on sensor size as counterproductive. The reason is Pixels capture Photons and not the size of the sensor. The information in this article is enough to improve your digital photography results. Practice regularly until you are more confident in these basic concepts. It takes effort to walk away from the oversimplified "size and capture" theory...

The sensor's Pixel area and pixel sensitivity reduce when we up the resolution. This should be general knowledge for all photographers. Instead, most photographers think it's all about cropping. Smaller pixel areas reduce the optical efficiency and ability of the pixels to resolve fine details, especially shadow detail. More pixels also increase the pixel wiring (control circuits). More components increase the sensor's noise floor. So much happens at the sensor's pixel level that it's dishonest and rude to make photographers think large sensors and cropping are the most important things.

For example, why should M43 photographers be interested in a used Panasonic GH5S?

Conclusion

This article teaches photographers more about the importance of pixels while studying the camera's image sensor. We also reviewed the most critical knowledge each digital photographer should have. The article also gives a new perspective on the different variables impacting the efficiency of the Image sensor. We also studied the role photographers have in achieving good image quality. We saw how photographers manage the image and video quality they get from their cameras.

What do we need for an equivalent image sensor comparison?

• The sensors should be the same type - (Standard CMOS, BSI, or Live MOS)
• They should have similar resolutions - We can't compare a 20MP with a 40MP
• The same firmware and pixel control circuits - That means the same AST and SNR
• The effective percentage pixel area should be the same for the different sensors
• The sensor sensitivities (optical and quantum efficiencies) should be the same
• And many more...

Pixel area is the only variable changing with a theoretically equivalent comparison. Let me know if you found an example of two or more sensor sizes (cameras) with these criteria.

Best

Siegfried

ISO Low, L100, L64, and Flash Photography - Part 2

Last updated:- 26th August 2023

Introduction.

What are the benefits of using ISO Low, L100, and L64, and does the camera's Dynamic Range (DR) change at anything other than its Native ISO? These and other questions initiated my journey to better understand digital cameras. I hope this article inspires you on your journey.

This article discusses the photographer's

role in achieving maximum sensor performance

How much should we know about the camera's Exposure Mix, SNR to ISO ratio, and Image Sensor? Do they improve our ability to manage the performance of the sensor? For example, does the sensor receive enough light at ISO3200, and how do we measure the light exposing the image sensor?

We know sports photographers need higher shutter speeds. For example, they will up their ISOs for higher shutter speeds in sports arenas. It's normal to have higher ISOs in good ambient light. Please take a moment to think about the following questions:

1. Do sports photographers risk having more noise in sports arenas? 
2. How do we know the image sensor received sufficient light?
3. When will you typically consider using a flash?

Any Olympus MFT camera with the f1.8 compact lenses from Olympus is a great photography solution.

The challenge editors have is collecting and sharing valuable and theoretically correct information. For example, I apply the info I discuss in my articles. The histogram, or monitoring of the sensor's saturation level, became part of the process I use to optimize my sensor's performance...

How do we measure the reflected light exposing the sensor? We know the aperture and shutter control the reflected light to the sensor. We control 3 of the exposure formula's variables on the histogram. They are the shutter speed, aperture, and ISO. Any exposure compensation adjustments change the light on the sensor with a fixed ISO and Shutter or Aperture Priority. That means the histogram shows the reflected light on the sensor if the ISO was set manually...

See this link to Part 1 of this series. Take a moment and study the illustrations in these 2 articles. They are designed to visually illustrate the information in this 2-Part series.

I am discussing the following:-

1. Introduction
2. A brief description of the digital camera
3. A brief overview of the image sensor
4. A brief description of the ISO function
5. The solution to the challenge in Part 1
6. ISO-Low, L100, L64, & Dual ISO
7. Why do we have ETTR?
8. Conclusion

Take a moment to study this illustration. It's good to understand the correct terminology.

2. A brief description of the digital camera

Each digital camera has a sensor. Some photographers consider it a mystical black box, and others as pixels and control wiring? That means the final image signal is a collection of pixel recordings or the product of an unexplained black box? Pixels typically receive highlight, midrange, and shadow information. This means most scenes consist of highlights, midrange, and shadow areas...

Varying exposure levels explain the noise from the Sony A7R IV in the image below. For example, shadow pixels are less saturated because they have less light. This means a lower SNR (signal-to-noise ratio) in the shadows. That's why we risk having more noise in midrange and shadow areas.

The Sony Full-Frame A7RIV w FE 24-70mm f2.8GM Lens - ISO3200, f7.1, 1/800 Sec. (We can explain the visible noise at ISO3200)

Digital cameras have analog and digital parts. The sensor's electronic (analog) components increase the sensor's noise floor. Some electronic components add more noise than others. This article focuses on the analog part of the camera and image signal.

The camera's digital section isn't our focus in this article because the digital image signal differs from the analog image signal. Digital noise is also treated differently by the camera...

Which analog components have more noise? The 3 components with the highest noise levels are the Image Sensor, the ISO Amplifier, and the A/D Converter. We do not control the A/D converter, but we do control the ISO and the reflected light exposing the image sensor.

Figure 3 explains the image signal pathway from the subject to the SD card. The aperture and shutter speed control the reflected light from the lens to the image sensor, and the ISO amplifies the recorded image signal from the image sensor. The following illustration explains the role of each of the main components in the image signal path.

Figure 3. (99% of photography cameras have this configuration)

Our focus is on the Sensor and ISO Amplifier because our exposure strategy impacts the SNR of the image signal. How does this happen?

1. Shutter Speeds and Aperture determine how much reflected light the sensor receives,
2. The ISO function amplifies the Image Signal plus the image sensor's noise floor.

Why do we have more noise at higher ISOs? Higher ISOs typically mean we have less reflected light on the sensor. Is it possible to control image noise? We learned that each sensor has a unique noise floor, and the ISO-to-SNR ratio influences the visibility (SNR) of the sensor's noise floor. This means experienced photographers always consider the level of luminance on the sensor.

What changes the size of the sensor's noise floor and the different noise types? For example, the sensor's noise floor is influenced by the type of sensor (Standard CMOS, Live MOS, and BSI sensors) or the number of electronic components in the sensor. See Figure 1 for a description of the noise elements in the noise floor. Also, see this video on the stacked BSI sensor in the OM-1.

Why are M43 sensors more efficient than Standard CMOS (APC) sensors? The Live MOS sensor uses one control circuit for each cluster of 4 pixels, and the Standard CMOS sensor has a separate control circuit for each pixel. This means Live MOS sensors have up to 75% fewer electronic components and are up to 75% Optically more Efficient. 

Higher Optical Efficiencies increase the Sensitivity of Live MOS sensors and the ability to capture shadow detail. A smaller noise floor means they have less noise per equivalent pixel area.

Improving the performance of the image sensor is as simple as

managing the luminance reaching the sensor...

The flow diagram in Fig. 3 highlights two camera components. Photographers should understand the noise behavior of the ISO Amplifier and the Image Sensor. Some confuse photographers by claiming some sensors have a separate A/D converter for each pixel. The flow diagram in Fig. 3 stays the same for one or more A/D converters, whereas the sensor's noise floor might increase with more A/D converters. More A/D converters simply means more electronic components plus noise.

The illustration (Fig 4) explains the SNR (Reflected-Light) versus ISO (Amplification) ratio.

Figure 4

It's always important to visualize the Reflected Light on the sensor. The above illustration shows the relationship between the ISO, image sensor, and the reflected light on the sensor. For example, a well-exposed image sensor allows for lower ISO values. This is why it's good to manually set your ISO and manage the reflected light exposing the image sensor. How do we add more reflected light to the sensor? With the aperture and shutter speed, reflectors, or a flash. These are the first steps toward better image quality and managing your image sensor's performance.

3. A short overview of the image sensor

Theoretically inclined photographers will value the articles below.

Please study the first 3 for this discussion...

• An article I wrote about DxOMark and IQ - link
• Evaluating different sensor applications - link
• Studying temporal noise and sensitivity - link
• Sensor discussion for mono cameras (PDF) - link
• Sensor discussion for color cameras (PDF) - link
• Interesting read on contrast limitation (PDF) - link

The following illustration helps us to master the digital camera and the image sensor. Each sensor has a unique photons-to-electron graph (Fig 1). Variables like AST, temporal noise, sensor gain, and DR are specific to each image sensor. Each sensor's photon-to-electrons graph is plotted with a fully saturated sensor. The photons to electrons graph are designed to assist us in planning, analyzing, examining our highlights and shadows, and determining local or global exposures. 

How do we apply local or global exposure adjustments? The Gradation function is one option, gradient ND filters are another, and a flash or LED light source is another.

Figure 1 - Each photographer should know the photons to electron graph. Study Part 1 of this series or this link.

Photographers only benefit from learning more about the image sensor and the information in this article. The info in this article improves our ability to:-

• Plan and select the right camera with an appropriate sensor
• Plan and execute technically challenging photo sessions
• Evaluate and analyze camera performance & images
• Improve their exposure and problem-solving skills

The information in this article is not intended to radically change your photography. The data was carefully selected to help you improve your knowledge of digital cameras. This article is more advanced but supports better exposure skills and higher image quality.

Figure 5.

What about the Fuji X-T4 or the Olympus EM1 III? The same information we discuss in this article applies to cameras like the Fuji X-T4 and the EM1 III. Studying the characteristics of these two cameras and using theoretical models like the photon-to-electrons conversion graph enables us to determine that both the X-T4 and the EM1 MKIII have specific strengths and are excellent tools. 

One of the most exciting differences is their image sensors, sensor sensitivity, and the noise floors of these sensors. It's new for crop sensor photographers to consider theoretical models because they've been taught to only think of sensor size, IBIS, ISO values below f5.6, and lens diffraction...

Figure 2.

How do we analyze the above image? I overlayed an example from this article onto the photons-to-electrons graph (Fig 2). The sensor was not fully saturated, the SNR was lower, and the noise increased in the shadows. This process of analyzing images helps us to develop a good feel for image sensors. What can we do to improve our image data in the shadows?

A less saturated sensor (lower SNR) and higher ISOs are the main reasons for noise. This reminds us of sensor sensitivity (image detail) and fully exposing the sensor (higher SNR). The Sony A7S III delivers good shadow detail because BSI sensors are more sensitive. Sony A7S III cameras are known for having a smaller noise floor or less noise to amplify at higher ISOs.

4. A short overview of the ISO function

The ISO function was not designed to change the gain of the sensor. The sensor's native gain is set at the factory. The ISO value is one of 5 variables calculating the camera's exposure. As seen in Fig. 3 & 4, the physical role of the ISO function is to amplify the image signal from the sensor. The image sensor is usually underexposed at higher ISOs. This ability to quickly review your camera settings and the relationship between the ISO and SNR is vital.

What is Maximum Sensor Saturation, DR, or SNR? The sensor reaches its full potential or has a fully saturated sensor, DR, and SNR when the reflected light is enough to fully expose the sensor. This is also the point at which the Photon to Electrons graph is plotted for each sensor.

"Size and capture" promoters claim "one sensor receives more light than another." This is repeated in almost every camera review. Universities teach that pixels are designed to saturate when they receive the right level of reflected light. The amount of reflected light reaching the sensor is linked to the ambient or available light and your camera settings. Photographers determine how the sensor performs and NOT the size of the image sensor...

Source: DPReview.com

Photographers decide how much reflected light exposes the sensor. How do we control the light? With the aperture and shutter speed. The key is to select an ISO for the scene and to manage the reflected light with the aperture and shutter or an external flash. Each photographer should know this. Why should we fix the ISO? We like to prevent the ISO function from changing our Exposure Mix. See this article for more about the histogram and ISO.

How did I create the following illustration? I did not change the ambient light..?

One can safely say the Exposure Mix of the camera determines the "working" Saturation and SNR of each pixel. For example, the displayed exposure on the camera will stay the same when we increase the ISO with 2 stops and decrease the reflected light by 2 stops. This means the image brightness stays the same, but the sensor receives 2EV less luminance. We basically managed the SNR to ISO ratio. The result is a less Saturated sensor with a smaller SNR. Try and plot this on the photons to electrons graph in Fig 4. This is an example of managing your Exposure Mix. What will happen to our image quality in this example? See the summary below:-

• Less reflected light means the sensor is less exposed (Aperture & shutter speed)
• That means the sensor is less saturated, and the image signal has a lower SNR
• A lower SNR with higher ISO amplification means we have more image noise
• It means less light with fewer details in the shadows and more shadow noise

You need to carefully plan your Exposure Mix. You are responsible for your image quality. A better way of determining the exposure is to start with the old exposure triangle. The next step is to know what you want and to manage your final exposure mix (ISO to SNR ratio).

Fuji X-T4 - I fully saturated the sensor (max SNR) at the native ISO with an optimum shutter speed and aperture combo.

When do we use higher ISOs? Photographers use more ISO amplification for higher shutter speeds and too little luminance to expose the sensor. See the summary below for why we need higher ISOs:-

1. With low-intensity illumination or available light and no available tripod
2. Indoor sports events, artificial lighting & high shutter speeds are needed
3. Outdoor or normal lighting conditions and higher shutter speeds (wildlife)

Does the DR of the sensor decrease at higher ISOs? No, the ISO setting does not change the available DR of the camera. The reason is the sensor's specified Dynamic Range stays the same. What does happen is the sensor is less saturated at higher ISOs. Study the exposure formula...

The Aperture, Shutter Speed, and ISO are variables in the exposure formula. They explain why the ISO is higher at lower luminance levels (Auto ISO). The exposure formula helps us to simulate and experiment with different exposure and ISO combinations (SNR to ISO ratio).

Image sensors are typically not saturated at higher ISOs. The sensor's "adjusted" DR is proportional to the saturation level of the sensor. It has nothing to do with the ISO setting because the ISO setting (amplification) is determined by the available light and the exposure mix. 

Think carefully before using any of the Auto Modes. We cannot manage our sensor performance with the ISO in Auto Mode. The reason is the ISO will change randomly in Auto ISO mode. It is only possible to control the exposure mix (SNR to ISO ratio) with the ISO in Manual Mode. 

5. The solution to the challenge in Part 1?

I asked readers to create 3 illustrations. Nobody did the challenge, which made me wonder, was it too advanced, or did I give too little information? The 3 illustrations are educational because they show the positive and negative image effects of applying the 3 practical ways of managing the image sensor's performance or the relationship between the ISO and SNR. 

Below are 3 ways of managing the performance of the sensor:-

1. Increasing or decreasing the sensor SNR with luminance (aperture and shutter Speed)
2. Amplifying or lowering your image noise (the effects of increasing ISO amplification)
3. Controlling the image sensor Saturation and SNR with an external light (using a flash)

How do these 3 methods impact the camera's image quality? A less saturated sensor means a lower SNR, less tonal data, and more visible image noise. A fully saturated sensor means good image quality.

How did I create these illustrations?

The 3 illustrations came to life when I searched for a simple answer to illustrate the benefits of managing the image sensor performance. I placed an A4-sized white paper against the wall and my older Olympus E-30 on a tripod. The illumination in the room stayed the same and was the primary light source. I created the 3 illustrations with this setup.

Why did I use my older Olympus E-30? Older cameras have more noise (noise floor) with more noise elements than newer cameras. 

5.1 Controlling the SNR of the image signal (Aperture and Shutter Speed)

This is the same as the SNR example in Figure 5.

I created the above illustration from a constant image signal amplification (ISO3200) and only controlled the luminance exposing the image sensor. The 0EV sample is 18% gray, and the rest of the 5 images vary +/- 1EV steps. This changed the reflected light intensity on the image sensor. Each of the 5 exposures changed the Saturation and SNR of the sensor. We can plot these 5 images on the photon-to-electrons graph. The final brightness of each sample was adjusted in PS.

The -2EV sample simulates an underexposed image sensor. That means sensor saturation is low at point A in Fig 1. The SNR is also smaller at -2EV and, therefore, the increased noise.

The manufacturing segment likes more information about the types of noise in the sensor. We should learn from them? For example, it's nice to have new AI noise reduction, but why not manage the visibility of your sensor's noise floor? The -2EV sample gives us a view of the different noise elements in the sensor noise floor. We know shot noise looks different from temporal noise. The +2EV sample shows the benefits of saturating the sensor.

What did we learn from this example? Apart from what I discussed, "managing" your image sensor's performance is the same as controlling the visible image noise. This means we can now make informed decisions about image quality or when buying new cameras.

What are the two most important things about the image sensor?

1. Sensor Sensitivity - This determines how image detail the sensor records
2. Sensor Noise Floor - Every image sensor comes with a unique noise floor?

5.2 The effects of ONLY using the ISO (image signal amplification) 

Figure 8.

I tested a different way of managing the image sensor. In preparation, please study Figures 3 & 4. It is critical to understand that even though the ISO is just another variable in the exposure formula, it's physically positioned between the image sensor and the A/D converter. In other words, the image sensor records the image and sends it to the ISO amplifier. We also see the effects of ISO amplification on the image sensor's noise floor.

How do we manage the image sensor with the ISO setting? Go back and study the first illustration. You will recall I kept the ISO constant for the 5 samples. That means some were brighter and others darker. I adjusted the brightness of each image (like ISO amplification) in Photoshop. Why do we increase the ISO? It is only necessary when we have too little illumination (underexposed image sensor). Like Photoshop, the ISO helps us to "correct" our final image brightness. It's critical to practice with the SNR to ISO ratio and this concept of managing your Image Sensor...

The ISO and shutter speed changed simultaneously (no increase in visible noise).

How did I create the illustration in Fig 8? I kept the luminance (aperture and shutter) constant to see if the noise would increase at higher ISOs (amplification). That means the saturation and SNR of the sensor stayed the same. This example shows the effect of amplifying the image signal and the sensor's noise floor. The ISO400 sample is correctly exposed, and the 18% gray version,

What do we learn from this illustration? This is something all photographers should know. The noise increases when we increase the ISO, right? We saw that the SNR of the sensor changes with a different exposure mix. The ISO amplifies both the image signal and the noise floor. 

Folks, we basically learned 3 things:-

1. The noise floor and the noise elements are linked to the design of the image sensor
2. Thinking and informed photographers will use a suitable sensor for the application
3. There's a tight balance between managing the SNR (Aperture & shutter) and the ISO

5.3 Using an external light source to manage the SNR

The above illustration is similar to the first. The difference is I used an LED light source to increase the illumination of the A4 paper. I then used my shutter speed to manage the sensor's saturation. I used the same ISO and controlled the luminance reaching the sensor with the shutter speed.

What do we learn from this example? Light and the ability of photographers to work with light are critical. The right level of illumination is vital for managing image sensor performance. Light determines if the image is flat or multi-dimensional. For example, anyone who says a tripod or an external light source (flash) is old-school should re-think.

6. ISO Low, L100, L64, ETTR, and Dual ISO

Most electronic components have a Linear Operating Range. The linear operating range for an image sensor is between points A and B in Fig 1. This means the photon-to-electron graph is linear and is predictable between points A and B. For example, a hundred photons will result in a fixed amount of electrons between points A and B.

The native ISO of the sensor is fixed with the sensor at full saturation. This means the DR will not increase below the native ISO of the sensor. The user's manual says the DR will decrease below the native ISO. While this is technically correct, ask yourselves, is this the only interesting information, or do these lower ISOs also help us to improve our image quality? Yes, they should because a lower ISO means less image signal amplification.

Why should we use ISO Low, L100, and L64? They offer better image quality because they use Less Image Signal Amplification. The aim of managing your ISO versus SNR ratio is to improve your sensor saturation and the SNR of the image signal. What about dynamic range? Dynamic range is a common weakness for all digital cameras. The solution is to learn how to work with the camera's dynamic range and the experience to make the right decisions for each scene. Typical options are the time of day, bracketing or HDR, Polarizer or ND filters, Log profiles, fill-in flashlights, and more...

Olympus EM5 II with Lumix 35-100mm f2.8 - ISO Low, f9.0, 6 Seconds (Done with a 1000ND filter and Live Comp).

Maria Schwartzmann used a unique example of why to use ISO64 on the EM5 MKIII and the Olympus LIVE COMP function - link (start at the 1:06 minute point).

How much less amplification do we have at L100 or L64:-

• ISO L100 is equal to ISO100 which is 1EV (Full Stop) less amplification
• ISO L64 is equal to ISO64, which is less than a full-stop ISO amplification

What is Dual ISO? Dual ISO is something we see on hybrid cameras. Dual ISO means having a second ISO amplifier parallel to the existing (default) ISO amplifier. The default ISO is calibrated at the base ISO of the sensor, and the 2nd Dual ISO is calibrated at higher ISOs like ISO800 (GH5S). The difference between increasing to ISO800 and selecting the 2nd Dual ISO800 is the first is amplified with 3 stops, and the second is set at the factory. Three stops mean a more visible increase in the sensor's noise floor. Depending on the camera, the same rules apply for the dual ISO amplifier as for the native ISO. This means the photons to electrons graph can be used for both ISO amplifiers. The only difference is the 2nd ISO will have a lower DR than the first.

7. Why would we use ETTR?

What is ETTR? It's nothing other than a method to improve the sensor's performance. For example, you can increase the exposure from 0.3EV to 1EV without clipping any highlights. Does that mean Olympus cameras are generally under-exposing the sensor? Yes, all Olympus cameras use a "safety" DR headroom. Almost all cameras set their exposure values at lower saturation levels. That's why the histogram is always a little to the left. See the illustration below.

To appreciate why Olympus cameras have a lower saturation level in Auto Mode, we need to understand the general-purpose nature of digital cameras. What is DR headroom? The camera doesn't use the full Dynamic Range range of the sensor in Auto Mode. That means it's better to use Manual Exposure Mode. It's better to manually control your Exposure Mix or ISO-to-SNR ratio.

What happens when we use ETTR? It simply means we will saturate the sensor. ETTR improves the SNR and DR while "shifting" the histogram to the right. The next step is to reset the 18% gray exposure values in WS. The benefit of using this technique is the sensor is at maximum saturation, DR, and SNR. The noise floor is less visible at both the native and higher ISOs. ETTR also improves the tonal data because the histogram shifts to the right. (Study this article at Adobe)

What if the DR quoted in camera reviews differs from the manufacturer's measurements? How do reviewers determine the DR? Do they measure the dynamic range, or do they calculate it? In other words, do they consider the DR headroom of each camera? Could we trust any DR information from camera reviewers pushing the "size and capture" theory?

What are the advantages of using older cameras? Apart from 2nd hand pricing advantage, the main benefit is more creative and artistic freedom. Older sensors are a joy when doing creative photography. If you like a camera with more creative freedom and sensor control, get an older Olympus camera. The IQ of M43 cameras like the EM1, EM-5, and E-P3 benefit most from ETTR.

Should we use ETTR at higher ISOs? We have seen that higher ISOs are used in low-light situations. In other words, the sensor is underexposed (between points A and B in Fig 1). Does that mean the DR of the sensor changed? The solution is to focus on the best exposure mix or use ETTR to get more light to the sensor. Everything we discussed in this article applies to higher ISOs. 

8. Conclusion

The "size and capture" theory cannot explain shadow noise or the differences between two 24MP full-frame sensors. Paid "size and capture" promoters will not discuss the evolution of image sensors because they cannot explain any of the improvements with the "size and capture" theory. They end up repeating the same lines they receive from their marketing managers. The info in this article is a theoretical explanation for the sensor. It helps us to answer almost any question about image sensors.

Many photographers prefer a more creative photography style. They will use their exposure settings to control the look and feel of the image. A personalized style is good because it's the artist's prerogative. This explains the popularity of cameras like the Pen F and E-P7. The info in this article supports creative artists plus those photographers asking for the best possible image quality.

Many support the idea that image editing should be a part of the image-taking experience. Olympus cameras make it possible with the Enhanced Raw Format and Workspace.

Also, see the more complex scene I discuss in this article.

Take care and God's Bless

Siegfried

You will find more information in the articles below:-

• Let's talk about ISO Low, L100, and L64 - Part 1
• The commercial "size and capture" theory - Link

Various References:-

• Equivalence theory for cross-format... - link
• Great video with Olympus photographers - link
• Interesting video discussing the OM-1 and exposure - link
• Understanding luminance for more control - link
• Great article and video on how to work with light - see the link
• Understanding camera performance Specs - link
• Fascinating presentation explaining sensors - link
• How to evaluate camera sensitivity - link  
• EMVA Overview - Imaging performance - link   
• Temporal noise reduction in CMOS sensors - link
• White Paper on the optical efficiency of the sensors - link
• The basics of the Low Pass or Anti Aliasing filter - link  
• More about the image sensor and the EMVA1288 - link 
• More about Low Pass filters and why they are used -see the link  
• A general page on consumer camera sensors from Sony - link