Crickets

I gave a yet another try to search the subject. Now I found an hour-long podcast, a conversation with Jeff Harmon and the site owner Bill Claff.

https://phototacopodcast.com/photographic-dynamic-range/
So I gave it a listen on my lunch break. What I picked up from it, plus some personal takes.

Firstly, PDR is indeed a measure of dynamic range in the sense a dictionary would define it. It's the difference of the whitest white (just before clipping) and the darkest black (where the camera can still maintain a reasonable SNR) expressed as log2 value.

The "photographic" in PDR comes from the fact that Bill incorporates circle of confusion to the numbers as a factor. The theoretical numbers are what pixel peepers can test to but having COC as a nice way to use mathematics to evaluate the overall picture most likely makes for more realistic numbers.

My take: in DXOMark you can choose between two sets of numbers: Screen (pixel peeping) and print (files normalized to 8 megapixels before measuring). This "print" normalisation kind of has the similar idea. In any event, packing more pixels means the COC changes and that generally reflects on the graphs in showing same-size, high-resolution sensors performing better. (Because you are not supposed to be pixel-peeping!)

Because a PDR chart after all is a DR chart, DxOMark's "Landscape" values are the ones that somewhat correspond with PDR numbers. Because of different math, factors and so on, there's a pretty constant difference of 3 EV between the measurements.

The discussion towards the end tangented on the subject of low-light sports shooting and how measured PDR might reflect on noise and image clarity----sadly Bill sidestepped the matter so it was left unanswered. I think this matter can be further researched independently of PtoP.

What did come up, is the fact that much like noise tolerance in general, what is an acceptable PDR is a matter of individual taste. Bill suggested the following: study the high-ISO images of cameras you know well, then check what PDR values these images correspond to. If you for example think that Panasonic GX85 at ISO 3200 is usable in some light, you can check the value being PDR 5.25. Coincidentally Panasonic G9 maintains the same PDR of 5.25 at ISO 6400.