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 them 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 influences Optical Efficiency and sensor sensitivity
6. More pixels means more pixel control wiring with more noise
7. M.Zuiko 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

The Aperture and Shutter Speed control how much light is reaching the film strip in analog cameras. Older film cameras have a mechanical ISO (ASA) adjustment dial. The ISO synchronizes the camera's exposure "calculations" with the film's sensitivity rating. The ISO is set once for each film.

The Aperture and Shutter functions are the same for digital cameras. The sensor's final sensitivity is measured and set at the factory. In other words, it's calibrated for your digital camera. The sensor's sensitivity doesn't change once it's calibrated. The ISO's function is different for digital cameras. It amplifies the sensor's output signal and is a critical part of the exposure formula. The ISO and the Workspace Exposure Compensation functions adjust the camera's image brightness.

The ISO also amplifies the image sensor's noise floor. It's, therefore, not correct to say the ISO creates noise. All sensors have an active noise floor when the camera is on. We can influence the visibility of the sensor's noise floor (image noise) with the SNR to ISO ratio. That means our goal is to improve the sensor's saturation and the SNR by "managing" the reflected light reaching the sensor.

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 distract photographers by claiming the A/D converter is part of the pixel's architecture. While correct in some cases, we know the basic flow diagram in the above illustration stays the same. One can say much about the technical details of digital cameras. The question should always be, will any new claims or information improve my photography, or is it more useless information?

3. How to manage the performance of the Image Sensor

This illustration shows how we manage the image sensor and the sensor's noise floor. A more detailed description of managing your sensor's performance is available here. (See 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 better 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 supports 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 an 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 each 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 at the sensor with a fixed ISO. Study the exposure formula for more info...

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 its native ISO and with the exposure 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 the absolute focus on sensor size 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 with 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 add more 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 similar
• And many more...

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

Best

Siegfried