Z DXOmark score question

Started 2 months ago | Discussions thread
bclaff Veteran Member • Posts: 8,744
Re: Z DXOmark score question

bayareaphoto wrote:
... I was lead to believe - by multiple quotations from variety of people on this board - that Bill Claff's PDR measurement is based on some accepted open methodology. Not being an expert in this field, I did not attempt to verify whether such claim was correct.

Yes, PDR is pretty well documented and has been replicated by others (for example Jim Kasson).

Note that PDR doesn't depend on a specific well controlled level of illumination (because it uses a wedge and locates the appropriate "patch" )

Also, whenever possible all in camera Noise Reduction (NR) is turned off when determining PDR.

... I have also read people say that the Dpreview was not shot in constant lighting conditions, which would definitely affect the observed results.

There are quite a few factors that can lead to inconsistencies in taking what otherwise might appear to be identical studio images.

In addition to illumination processing of the raw data to create the mage might not be identical despite best efforts.

Ultimately, I take no sides. I will happily accept any theory which explains the inconsistency between Bill Claff's PDR table (EV value) ranking, on the one hand, and the visible results in Dpreview comparison tool, on the other, in the part that concerns the Canon 5DS and Nikon Z6 noise in low light, Comp, ISO 12,800. If the PDR measurement is at fault, so be it. Ditto for the Dpreview tool.

Perhaps, because of differences in the methodologies, it's simply an "apples to oranges" issue; the results are simply different.
That said; because of what I know I suspect more variability in the studio tests than PDR.

This is ultimately important for many people who make decisions based these two sources. This is why I was not letting go of this topic. Thank you and mostlyboringphotog for willing to walk this walk.

Ultimately the photographer is going to post process is a particular way (because of taste or habit) or perhaps simply accept the out-of-camera JPGs most of the time.
If the decision is a "close call" the best strategy is to rent and determine how a camera performs under that photographers conditions.

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Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

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