Those are handy graphs and examples.
I think most people want to see hard, cold, objective measurements so that they can make judgments comparing cameras or ISOs, etc., so that they can come up with easy rules for what ISOs to use, etc.
But the problem is that all of this is subjective in the end.
It's the same with audio, too.
The point at which you suddenly decide that the SNR is too bad to tolerate depends on a lot of factors and personal taste, etc.
Back in the days of analog tape, there was a lot of personal taste involved in how "hot" to record things.
Record hotter, and the tape noise ends up lower with respect to the average signal level. But you have higher levels of distortion in the loud passages.
Record lower, and the tape noise ends up being higher with respect to the average level, but you have lower distortion in the loud passages.
So different people, using the exact same recording system, ended up with different signal to noise ratios in their final product. But who's to say which "sounded better"? I tended to find tape hiss less objectionable than distortions. So I tended to record fairly low. Others preferred to lower the tape hiss by recording hotter, and could tolerate the distortion in the loud areas in trade for that.
And then we get into the question of "pattern noise" versus random noise. I suspect this ends up being very similar between audio and digital image capture, too.
If the non-signal artifacts in the "recording" have no pattern to them (that is, they're truly random in nature), then our eyes or ears can put up with them at a much higher level than if that non-signal artifact has a discernible pattern to it.
Vertical or horizontal banding in an image is a lot like having a low-level "whine" in the background of a recording versus random noise. The relative power level of that "whine" may be the same as the power level of the random noise, but your ear/brain can pick it out easily, and it'll be annoying. And the relative power level of a bunch of lines in an image might be no higher than another image's random noise, but the image with the lines in it will be very ugly to most people.
Our brains tend to look for or listen for patterns. So reducing pattern noise is paramount IMO.
It appears that the 7D is pretty good in this regard.
To me, therefore, I'd probably tend to find its DR to be greater than a camera with the same "measured" DR but which had a more defined pattern to it's "noise".
If we got a batch of film that was made when the coating machine was having a problem, and it had an uneven coating thickness such that there were horizontal "bands" in it, people hated it. And yet, the intensity of those bands didn't need to be very great for it to be unacceptable. You might even argue that this "banding" was below the "noise level" of the grain. But it still looked awful.
So I think the nature of the "noise" in question can have a huge impact on whether or not it's acceptable.
Two cameras or ISO settings might have the same DR or SNR by some measurement, yet the images may not look the same.
--
Jim H.
