D200 vs D70 Dynamic Range graph

Started Jan 30, 2006 | Discussions thread
Bill Janes Senior Member • Posts: 1,727
Re: Problems resolved

davexl wrote:

Hi Bill - what tone curve have you go the camera set to? Normal or
Auto?

Normal

And spotmetering those shadows would tell us a lot about the
dynamic range of the target.

When does your transmissive test target arrive?

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Regards,

David F.
Melbourne, Australia.
http://www.pbase.com/davexl/folio

The transmissive target arrived and further testing has resolved the previously noted differences between my results with Imitest and David's characteristic curve from multiple exposures of a gray card. Actually, they give the same results if you use the normal Nikon tone curve for both tests.

The Nikon curve rolls off the darker values toward zero much more rapidly than Adobe Camera Raw or a literally applied gamma of 2.2

Here is the plot of the RAW file with no gamma correction tone curve. The plot is linear with some flattening in the shadows consistent with flare in the lens and camera box:

Here is the Imitest plot of the Stouffer target with Nikon Capture using the normal contrast setting.

And here is the plot of the same image converted with ACR using default settings. Note that there is much less roll of of the darker tones.

Finally, here is an Excel chart showing all of the above results together in a log-log plot similar to Imitest's. For simplicity all pixel values are expressed in 8 bit (0..255) units. David's results are presented as yellow triangles and closely track the Nikon Capture conversion. Also shown is a literal application of gamma 2.2 to the raw data. It is necessary to roll off the shadows at some point, each EV halves the exposure and it would take 12 halvings to go from a raw pixel value of 4096 to 1 and a print does not have that many zones.

Here is the same graph with linear-log scaling (similar to what David showed). IMHO, the relationships are much better appreciated in the log-log plot, which is probably why Imitest uses it.

As Julia correctly stated: "David, that in no way characterizes cameras. What you presented is dynamic range of your preferred processing of the images." The converter software has a profound influence on the results.

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Bill Janes

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