ISO Low, L100, L64, and Flash Photography - Part 1

Last update:- 16th January 2023

While working on Part 2 of this article on ISO and Image Quality, I thought it was a good idea to set the stage with a few random thoughts and a basic challenge. Thinking about it, every photographer should develop the ability to analyze digital images. A good understanding of the digital camera and the ability to apply this knowledge benefits all digital photographers...

Taken at a constant luminance perspective and a variable image signal amplification

Taken at a constant image signal amplification (ISO3200)

You are welcome to try the following challenge. Place an A4-sized white paper against the wall and your camera on a tripod. The challenge is to recreate the above 2 illustrations. The info needed to create a basic plan, take the images, and build the final illustrations, is all in this article.

Olympus Pen F with 25mm f1.4 Leica, ISO80(Low), f3.5, 1/1600 - Edited in DxO PL-4 (See more info further down...)

Here are a few general questions for you:-

• Prep a short explanation of what happens inside the camera for each illustration
• Think of a few examples and list the benefits of knowing your digital camera...
• Why do you think it's safe, or not safe to use the ISO Low, L100, or L64 options?
• Most social media experts tell us it's not OK to use ISO Low, L100, or L64, why?
• Which of the 5 images in each of the above illustrations are 18% gray samples?
• What is the link between the Zone system, 18% gray exposure, and the ISO setting?
• Study the photons/electrons graph below. Does it apply to all or only some sensors?

For more on how to plan your own strategy, study these articles:

• Start from basics and learn how to record more image data - link
• A better way to control the camera is the 2 Step Exposure Technique
• Why is sensor sensitivity so important? - article (Important info)

A few general thoughts...

The reason photographers should distrust any sensor size references is it's normal for digital cameras to have image noise. What determines this image noise? Most photographers are never told that all sensors come with a native noise floor. Should we trust those reviewers who promote sensor size or write biased camera reviews? This is likely the main reason we don't see discussions about advanced digital photography techniques, like how to use ISO amplification correctly, or how to manage the performance of the Image Sensor. (See this link)

For example, why was the old-school Exposure Triangle never improved? Especially while it's used to train photographers on digital photography? How will they ever master advanced digital camera skills like SNR, sensor saturation, or image signal amplification with an outdated triangle? 

Is size a reasonable measure for IQ? We know pixel area (size) is one of many variables to impact the Optical Efficiency of the image sensor. So why focus on only one of many variables? Well, looking for answers is like finding a needle in a haystack. A more reliable way of rating image sensors seems to be Sensor Sensitivity (Optical and Quantum Efficiency).

To illustrate the oversimplicity of the "size and capture" theory, study the illustration below. This illustration offers more information about the image sensor, the noise elements in the sensor noise floor, and the effective dynamic range of the sensor. Other than the "size and capture" theory, which cannot explain shadow noise, those who master the principles illustrated below will have a strong theoretical foundation. They will improve their analyzing and sensor performance skills.

For example, take a moment and consider the graph below. The horizontal axis is the reflected light or photons hitting the sensor. The vertical axis represents the converted electrons. The sensor's full saturation capacity is reached with a fully exposed sensor. Plot the saturation for shadows or low-light scenes. How does this impact the performance of the image sensor? What happens to the SNR in the shadows? What does the histogram look like for an under-exposed sensor? These are simple questions every digital photographer should be able to answer...

Does the size of the sensor backplate "capture" photons? The answer is NO! We know pixels capture photons and pixels (photocells) convert photons into electrons. This is the main reason why scientists improve pixel (photocell) sensitivity and why they don't design bigger sensors. That said, the size of the sensor does play a role. Any idea what? Think of image effects like background blur.

 

Olympus photographers are familiar with 12MP or 20MP (MFT) sensors. The pixel diameter of 12MP sensors is almost double that of 20MP sensors. We know the EM1 III has one of the most sensitive M43 sensors and delivers far superior IQ to any of the older 12MP MFT sensors. Ever wondered why? Could one of the reasons be, that sensors with lower Temporal Noise have cleaner images? 

Study DxO Mark results for the EM1 II sensor.

The more we learn, the more we see what happens with image quality...

Another illustration with info on how to manage the sensor at ISO3200.

Let's talk about the physical size of mirrorless cameras? The size of the image sensor influences the physical size of the camera? The reason is the lens image circle needs to cover the full sensor. This impacts the size of the lenses, the camera energy needs, heat management, and the effectiveness of features like IBIS. Digital cameras are basically built around the image sensor. The penalty for cutting corners is overheating, lower efficiencies, and less reliable cameras and lenses. 

Separately from any fixed mechanical design criteria, scientists focus on materials and the electrical design aspects of creating more sensitive image sensors. This represents a better way of designing new cameras and improving Sensor Sensitivity. For example, typical improvements in image sensors include replacing older wired functions with modern software or AI solutions... 

As you know, Olympus and Panasonic were the first to introduce mirrorless cameras. Did they also establish the mechanical design benchmark for mirrorless cameras? For example, what is the built-in safety margin on M43 cameras? When you see similarly sized APC or FF cameras, does it mean the M43 camera is over-designed, or are these APC and FF cameras under-designed?

How much image noise is added to the noise floor for each 1-degree increase in temperature..?

Try this quick experiment and point a light source to your PC. Which of these sensors is receiving more light?

If someone says one sensor captures more light than the other, then I cannot help to think, is this statement theoretically correct? I was searching for information when I saw this review. I could not help asking, is this just another Undisclosed Promotion? What if the "more light" benefit was only 0.0002% while those bigger sensors were 10% less efficient? One would like to think, it's all about the efficiency of the sensor when converting photons into electrons, right?

See this discussion. It's a great example of why photographers should push manufacturers for better information. Also, do a quick search on the implications of "Undisclosed Promotions"...

Final comments on the two images in this article

Take a look at the 1st image in this article. I have set the exposure for the bright areas (sky). I wanted the sky with darker shadows. At home, I did a quick test to study the visible shadow noise when I increased the shadow brightness. Editing the raw file in PhotoLab 4, it was possible to extract cleaner image details from those same shadows. Does that mean the image had enough available information in the shadows or is it only PhotoLab doing a great job?

The above example shows the jpeg on the left and the edited raw version on the right. The image was exposed for the shadows, which over-saturated the sensor in the bright areas. It did not clip the highlights while pushing them hard. I tried different editing techniques to get the most from this "data-rich" raw file. The most pleasing result was editing the raw file with Aurora into an HDR image. Did I push the image sensor too hard, or is it OK when we push the image sensor?

The selected images demonstrate the different technical aspects discussed in this article plus it shows it's safe to work with ISO Low on your Olympus Pen F. The same is true for ALL cameras. Don't we benefit more from working with a fully saturated sensor and resetting our final image "brightness" in Workspace? Why is there a link between the camera (Live View) and Workspace? Why sensor size and then push restrictions like don't use the extended ISOs on your M43 camera..?

More about Managing your Image Sensor and ISO Amplification in Part 2...

Finally, what's better, exposing creatively, or saturating the sensor?