I also don't know what Danne has done "under the hood", and so it may be that the test is invalid for actual ISO comparison.
Analog gain lowered and CMOS[0] overridden for higher ISOs; see his commit.
For example, ISO 100 presets are:
- with his "iso100" option enabled: CMOS[0] as for ISO 200, analog gain 512
- with "iso100" + "12-bit": CMOS[0] as for ISO 400, analog gain 250
- with "iso100" + "10-bit": CMOS[0] as for ISO 1600, analog gain 60
I believe you have use one of the last two presets, just not sure which one.
In my tests, reducing analog gain only improves things by about 0.1 EV.
In other words, I'm pretty sure the results you were getting were 0.1 EV actual improvements, and 1.5 ... 3 stops were misunderstandings (possibly coming from the mislabeled ISO values in crop_rec menu). I wanted to prove it on your own images, but that requires identical test conditions for each setting (which you did not provide).
You made a very strong statement:
Ok guys, here's the proof everyone needs...
yet, you did not provide a valid proof.
I'm a happy camper getting excellent results, and the last time I checked, that's what really matters...
Yet, this particular topic (ISO tweaks) was about getting results *better* than with stock Canon ISOs.
My argument is that, in Danne's build, the improvement is about 0.1 EV over stock Canon ISOs (according to my measurements). In your example, the shadow difference is much stronger than that, but
I'm pretty sure that difference is *not* an improvement over stock Canon ISOs (except for that 0.1 EV, which is not going to be noticeable without careful examination).
There's a bit of loss of highlights, but for practical purposes it is negligible.
Pretty sure the loss is about 1.9 EV if you have used the 12-bit "iso100", or 3.9 EV if you have used 10-bit "iso100". Clearly negligible
