Today I posted a brief article in the Technique section about Dynamic Range. Short version: there’s no specific, agreed upon definition of dynamic range.
Unfortunately in photography today we have a lot of those “no one agrees” type definitions. Consider depth of field, for example. Technically, only one flat (or curved) plane is in focus. What depth of field tries to define is “what’s acceptably in focus.”
Unfortunately, a ton of variables come into play for determining acceptable focus, and not everyone agrees on the variables, let alone the results. The much used so-called Zeiss formula sets specific eyesight, viewing distance, and print size variables, for instance. Do you know what they are? Other depth of field thesis’ use different variables. No agreement.
Diffraction is another area where there’s definition contention, though less so today than there used to be. Why? Because with some early digital cameras the complete Airy disc wasn’t recorded over multiple photosites, it landed on just one, thus couldn’t really impact edges. Even as things changed so that diffraction was recorded on adjacent photosites, the demosaic used to get RGB values may or may not have picked up the full diffraction impact, particularly because the actual diffraction varies with light spectrum. Now that we have high megapixel count image sensors, the Airy disc is getting well-recorded, regardless of demosaic. So the term “diffraction limited aperture” has different meanings to different people, even today.
And let’s not get started with ISO, which is a standard, but a standard that’s interpreted differently by some.
We have all kinds of claims navigating the Internet these days (e.g. “15 stops dynamic range!”), but those claims aren’t useful without definition. We then get people arguing over claims (“my camera has more usable dynamic range”), but again lack of definition gets in the way of truth.
I’ve mentioned apples-to-apples before, but it seems that the Internet is now full of apples-to-whatever_makes_my_product_look_better comparisons. Camera and lens maker marketing departments aren’t immune from this, either.
So how do you figure out what’s real and what applies to you? You test. To your standards and needs.
For nearly 30 years I’ve been an advocate of “learn your tool” when it comes to cameras and lenses. The first thing I’m doing with any new camera or lens is run it through a bunch of my personal semi-standardized tests to see how it performs. That usually is enough to inform me as to which standardized and carefully controlled tests I might need to make to further understand how the product performs.
For instance, noise propagation at various ISO levels. I have a couple of quick tests I’ve used for years that allow me to quickly make an assessment of what the camera can do. They’re not specific or controlled enough to give me clear, useful results, though. What those quick tests generally tell me is where I need to spend time assessing controlled results. Often I can tell whether something changes at specific ISO values (I’m not just talking about dual gain, but I noted very early on that something was different about the low ISO on the R6 when I began applying my quick tests, and often I see some sort of scaling or noise reduction kick in on a new camera at high ISO values).
With some cameras I spend more time learning how it deals with something specific. For instance, I take astrophotography with my Z7 II or D850. So how they handle very long exposures is of deep interest to me and requires some rigorous testing to understand what might be happening in the DNs and what might be causing what I see. But a D6? Nope, I don’t use that camera for astro work, so I don’t need to do more than quick testing at longer shutter speeds.
What amuses me is when someone is quibbling over pixel-level issues in edge circumstances, but is using their camera with a low cost superzoom lens. That’s why I can’t perform every test for every person for every photographic situation, and thus advocate that you do your own testing.
While “good enough” is not a trait I seek out in my gear or work, if it is for you then you have different standards, and a more casual testing of your new gear may be all you need to do. The more you want to be Ansel Adams (or follow my “best possible digital capture” mantra), the more you need to be diligent about testing every aspect of your new gear the way you’re going to use it (again, might not be the way I or others would use it).
Somehow I doubt we're ever going to see agreement on what some critical terms mean. And yet that (certain terms) seems to be what most of you are obsessing over at the moment.
We have a linguistics problem in photography, and pretty much always have. Even Kodak and Ansel Adams disagreed about what gray meant. I don't see this changing any time soon, and it's not my role, nor do I have the audacity to suggest, that I can fix that.
(We also have semiotics problems in photography, too. But that's another story for another day.)
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I'm appreciative of those site readers who've caught me in conflict with word usage or definition from time to time. It's hard to write (and self-edit) as much as I do without catching myself in a contradiction in usage from time to time. When that happens and I'm made aware of it, I try to go back and make things "align" better in the thousands of pages on my sites, but I don't always catch every instance. Nor would the best proof reader/copy editor I've ever used, though my ex-wife (a copy editor) managed to catch far more of those inconsistencies than you'd believe was possible.
