Archive for April, 2021

Many people may be confused about the term dynamic range and how this camera has more of it than that camera and all the usual hype and sometimes BS about the subject. But the real question is, what is it? And does it matter?

The latter question is easy, yes, yes it does matter. But the important question is: What is Dynamic Range?

Dynamic range is basically a measure of how large a difference between the lightest part of an image and the darkest part can be resolved with measurable detail. It is directly akin to the film days when we used to call it exposure “latitude” but the term “dynamic range” is derived more from the audio world as signal processing is relatively new to photography but has been around forever in audio.

Digital cameras use a sensor that has millions of photosensitive cells. Each cell is capable of absorbing a specific amount of light before it becomes completely saturated and can absorb no more. When that cell is saturated it sends a signal of pure white. This is sometimes called clipping as the signal is actually higher than the cell can report. This makes highlights devoid of detail. Like wise there is a base line level of noise produced by the electronics that can appear in dark areas of the image when under exposed. The range between the darkest measurable details and the brightest measurable details is what dynamic range refers to. It is usually measured in an EV value or more simplistically in “stops.” A good film back in the day had 12-13 stops of “latitude.” Todays premier digital cameras can beat that handily sometimes pushing towards 15 stops of range.

I have discussed in the past the notion of larger pixel photo sites and how those tend to yield high dynamic range because they can absorb more light. Imagine two cameras with a 24mp sensor. Let’s say Sony A7 III and Sony A6500 for example. Both cameras have the same pixel count but one has a full frame sensor that is 24x36mm the other is APS-C with 15.7×23.6mm. The pixel density on the smaller APS-C sensor is more than double. This means the pixel photo sites are much smaller and therefore cannot absorb as much light. In the early days of digital photography this was a major inconvenience, but todays technology has allowed manufacturers to create software and image processing hardware to level the playing field up through mid ISO ranges below 6400. Beyond 6400 there is still a measurable advantage to less pixel dense sensors.

There is a bit of a myth that the advantage of higher dynamic range is limited to high ISO performance. When shooting JPG out of camera and no post processing this is more or less true. But shooting RAW and using sophisticated post-processing software like Photoshop the dynamic range becomes extremely important even at base ISO levels of 100.

Sometimes a photo may have been taken in undesirable lighting conditions with an extreme variance in stops between the dark areas and the light areas. Sunsets can produce this effect for example. If the photographer prefers a silhouette sunset then dynamic range is not a major concern. But what if foreground details are needed without losing the blazing colors of the bright sky? Back in the film days a graduated ND filter was one way to control the variance between a sky and the foreground. This was fine if you had an even straight horizon, but that obviously is not always the case.

The two images below are actually the same image. The first image is unprocessed straight out of camera. Lighting is awful with the blazing sun in the frame and an extreme difference between the dark areas and the brightest spot, the sun. The sun is clipped and that is fine especially since people are used to not being able to look at the sun directly anyway. But there is still a substantial amount of detail the photo sites picked up in the dark areas revealed with some basic camera raw adjustments. The second image reveals these details by reducing the highlight exposure and increasing the shadows. How much you can “push” them depends largely on the dynamic range. Additional tweaks could lead to even better results. None the less it is the dynamic range that allows for these corrections without severe noise. This was taken with a Canon EOS M6 mk II which is a 2019 APS-C camera. My R5 would have yielded better results in the shadows but this particular image was good to go with roughly 13-14 stops of DR. The image is intended to show progress on a construction site and the extra DR allowed for a relatively well exposed sky and background without losing the details down on the worksite or on the tower crane.

Generally speaking it is better to over-expose a digital sensor than under-expose. So long as the camera has good dynamic range, shots will look better slightly over-exposed and then corrected with highlight and shadow controls. Under-exposure tends to result in digital noise when pulling up the shadow detail. The greater dynamic range cameras such as Sony’s 24mp A7 III will do a great job of not clipping the highlights even when over-exposing the image thus allowing for less shadow manipulation that often reveals digital noise. Pulling up hard on shadows is a major noise producer.

Technology is advancing fast and sensor hardware and processing software are making even small sensors like micro 4/3s and 1 inch, able to produce 11-12 stops of dynamic range or more. But all of this technology is also available for the larger sensor cameras and that means even MORE dynamic range is possible with APS-C and full frame cameras.

So where is the “BS” then? Well that is a bit of an issue with getting beyond a reputation. 15 years ago you could take a Canon camera and put it up against a Nikon camera of similar cost and specs and see noticeable differences in how the cameras rendered images. Canon built a reputation for excellent color rendition that was largely applauded across the board in most industry reviews. But Nikon was constantly producing higher dynamic range that resulted in clearly superior high ISO performance. The straight out of camera performance was important back then because the amount of post processing manipulations that were possible without over-processing the image were much lower than today. It should be noted that in those days shooting at 1600 ISO was a big deal and any higher was sketchy. Having an extra stop of high ISO performance was a real advantage, and Nikon had it.

Fast forward to modern times, and both Canon and Nikon have made huge leaps in technology. Nikon which uses Sony made sensors still has better dynamic range than Canon but now the difference is maybe 2/3 of a stop and both are so good there are few lightning scenarios that either cannot combat. It’s like Lamborghini bragging about their top speed is 230mph and Ferrari is only 227mph. Peter Griffin says it best at this point, “Who the hell cares?” Canon still brags about their “colors” and Nikon and Sony still brag about the dynamic range, but these days it really doesn’t matter much. They are pretty close.

Where this discussion really matters is when choosing older cameras. The further back you go the more important a large sensor is. An original a7 is going to be much better at dynamic range than an old a6000. But a new a6600 might perform equally well to the a7-II due to advances in processing and sensor technology. My EOS M6 mk II has a higher pixel density than did my EOS M5 but it seems to be even better at dynamic range. Of course it has a 4 year advantage in technology sporting the faster and more powerful DIGIC 8 processor vs the DIGIC 7 and it has a new sensor design vs the M5. My M6 mk II has better dynamic range than my old 5D mk III did which had 1/4 the pixel density of the newer M6. If your camera has 13+ stops of dynamic range you are doing just fine. You don’t have to shoot full frame to get the dynamic range these days, there are still other excellent reasons to do so however. That will be another post 🙂

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