Photographic Dynamic Range (PDR) is a More Useful Measure than the DxOMark Landscape Score

Started Apr 17, 2015 | Discussions thread
Detail Man
Detail Man Forum Pro • Posts: 17,073
Re: Regarding PDR of Sony A7S at ISO 409600

bclaff wrote:

Horshack wrote:

bclaff wrote:

I assume you're trying to show that the Sony A7S has more DR than the 0.93 that PDR predicts at 409600.

But I think you're forgetting that there is an acceptable quality factor built in.
When I put your image on my screen at 8"x12" and view it at a reasonable distance I don't find it acceptable (usable perhaps, but not acceptable).
PDR predicts that the brightest 0.93 stop in such an image if ETTRed would be acceptable. (Maybe up by those stairs)
I have some other input on this matter but since it's really not directly on the topic of this thread I'll start another when I get my act together.

You proposed two foundations for your 20:1 SNR cutoff - human sensory limitation and acceptable quality. I believe this image demonstrates we can perceive more than the 1EV in this image. As for what is acceptable quality that'll always be up for debate.

No disagreement.

Just to recap.

I chose SNR = 20 which ISO says is "good" (They also say SNR = 40 is "excellent" )
ISO also says SNR = 10 is "acceptable"
As I understand it, SNR = 5 is considered the limit of usable feature detection.

Just out of curiosity, are you saying that the "International Standards Organization" ("ISO") has deemed this or that image SNR as "acceptable" ?

So certainly, depending on what you are after, you could add stops to the PDR value to suit your particular purpose.

The image is indeed "a mess". So much digital scaling is taking place that non-zero valued RawDigger histogram bins represent only 25% of the total (way down in the "boondocks" below)":

That said, landscape photography (shot in relatively low, indirect natural lighting) can indeed include shadow areas approaching/ including Read/Dark noise levels. I don't really "get" the point of a debate as to whether or why such occurances would or would not be "acceptable". They just "are" ... and in processing one may want/need to deal with them.

The "debate" seems to be whether some DR/SNR "metric" should "bother" with such "depths".

DM

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