It is a fact that ISO has no direct control over exposure.
See? Here is where the problem lies. Changing the ISO has an effect on the image.
Yes, but not directly on the exposure. In five of eight available modes, It has no effect on exposure, In the other three modes it has an indirect effect. In all modes it has a direct effect on image lightness. In three of those eight modes the indirect effect on exposure cancels out the effect on image lightness. in these three modes the indirect effect on exposure results in a negative net effect on noise. In the other five modes, if there is an effect on noise, it is a positive one (noisiness is reduced).
It applies gain in-camera so the apparent effect is increasing sensitivity,
if input sensitivity was actually increased, then more light would be captured, and the SNR would increase in proportion to the square root of the increased amount of captured light. But that is not what happens, The direct effect on SNR is almost always less, usually much less than what you'd get from an an increase in light. And if the camera is in a mode where it tries to maintain a target lightness, it decreases the exposure, resulting in a net decrease in SNR, though often slightly less than the decrease that would come from a reduction in exposure alone.
even though it does not do so technically
It does not do so at all. And it doesn't have the same net effects.
. And this is where many explainers fall down. So focused on the technical correctness of one aspect that they fail to communicate effectively.
If somebody manages to clearly explain an incorrect model, is their communication effective in a sort of way that is desirable?
A simple sentence that nonetheless manages to contain three inaccurate statements.
ISO increases the gain in the sensor,
Not necessarily. On a few cameras, variable gain is not used at all. In quite a few other cameras, variable gain is not used to implement certain ISO increases. Increasing ISO, in general, cannot correctly be described as applying gain.
in effect amplifying the actual light received,
No, that is not the effect. If more light was actually received the effect would include an increased SNR proportional to the square root of the increased light received.
akin to turning up the volume on your stereo.
Akin in the sense of third cousin twice removed, perhaps. The analogy is wrong both with respect to mechanism and to effect on output fidelity.
Rather than going into detail on what ISO does not do, simply tell what it does.
It controls the mapping of photodiode charge on to digital numbers. For a given number of photons captured, it determines what number will be stored in the image file.
.So, in a debate between people who advocate and teach an accurate understanding of how digital cameras work
No, this is what some of you do not get. It is not just the information imparted, but the way it is.
Certainly some people do seem to object to the style of presentation instead of the information content. It has been suggested that's because the resistors of the message have finally learned they have no basis to object WRT information content .
You do not impart accurate information if you audience doesn't understand what you are attempting to impart.
Agreed. That's why many of us try to remove barriers to communication, such as incorrect use of technical terminology or incorrect conceptual models.
and others who passionately, almost dogmatically defend a popular but factually wrong understanding of the same subject,
There are those who will defend inaccuracies regardless. I'd wager there are many more that would listen if the experts were better instructors.
If you'd helpfully suggest edits to improve the comprehensibilty of what I write, I'd pay attention.
Knowledge ≠ the ability to impart it well.
indeed.
I'm not sure that I'd agree that the average communication ability of these who explain the problems with the ET is below what is needed to communicate effectively with the average reader here. But I'm sure we could all improve if some constructive feedback was provided. That's as rare as hens teeth though.
