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

Started Apr 17, 2015 | Discussions thread
Horshack Veteran Member • Posts: 7,912
Re: Regarding PDR of Sony A7S at ISO 409600
3

bclaff wrote:

Horshack wrote:

Horshack wrote:

bclaff wrote:

Horshack wrote:

bclaff wrote:

However, normalized read noise is not photographically relevant; and the DxOMark Landscape Use Case score is supposed to be a photographic use case.

Read noise is not relevant to whose photography specifically?

I think I could have been more explicit.
I mean that a measure that is solely read noise and has no photon noise component is not photographically relevant. (It has engineering relevance.)
If we disagree on that, I guess we should just let it go!

The problem with randomly selecting an SNR cutoff for DR and calling it relevant is that it's only relevant to some and not others.

I don't believe the PDR cutoff is random at all.
It is based on the acuity of the human eye and established values for image quality.

Regards,

I've got to run out but this is an interesting discussion to continue later. Until then here are two A7s images for thought - at their full native resolution - one at ISO 100 and the other at 409600 - at the same relative exposure. According to DxO the A7s has 5.76DR @ ISO 409,600 (normalized to 8MP) vs your PDR measurement of 0.93. Looking at the ISO 409,600 image do you believe we cannot discern > 1EV of DR in it?

A7s ISO 100 4 seconds

A7s ISO 409,600 1/1000

Here's perhaps a better ISO 409,600 example, with the scene DR more visible. raw is temporarily available here.

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.

Regards,

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.

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