Dynamic range is over rated

Started Apr 20, 2012 | Discussions thread
Rick Knepper
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5D2 vs. D3x RAWs link for download
In reply to tony field, Apr 21, 2012

The link to the RAW images:

https://www.box.com/s/d372d553e016ffd06312

I followed your recipe as best as I could but may have misunderstood some portions of it. I own this grey card but never use it. As you will see, I placed the grey card on a stand in direct sunlight and metered and focused on it. If I should have used the grey card differently eg to create a custom WB or metered another part of the scene, let me know.

I set the aperture to f11, a typical landscape aperture for me. The Nikon returned a shutter speed of 1/50 & the Canon 1/80. I shot a set just like that. Then I EC'ed the Canon to 1/50 and shot another set.

I felt like for those who really want to get to the bottom of this, getting the RAWs and doing their PPing would be more valuable for the individual. For my purposes, I just turned every slider to zero in ACR and got my answer.

If you feel like I should modify the test in some way, I'll be glad to redo it tomorrow morning.

tony field wrote:

Your experiment is a difficult one to do well and get useful information. No matter what you do, the tecno nerds will always find dozens of experimental errors in what ever process you evolve

The cameras' evaluative system are different and do not result in the same exposure for a given scene. In addition, they have different interpretations of ISO. To somewhat get around these problems, I think I would suggest the following....

1. Set the cameras to the same ISO.

2. Set the lenses to aperture priority and choose the same aperture on both lenses. This will provide identical DOF for image evaluation and, when comparing detail recovery, it is easier to judge when comparative images have identical sharpness characteristics.

3. Use a grey card (roughly 18% - it can be any grey in the general area, however exactly 18% would please the critics - the camera meter will interpret this as "exactly 18%"). This will be the thing that allows you to approximately normalize the exposure since I would not trust the evaluative metering to do this for the experiment.

4. Use the spot meter on the grey card on both cameras and determine the shutter speed (shooting in aperture priority). This provides a known tonal/exposure reference point when you evaluate images - and will allow you to judge the camera interpretation of ISO as it relates to exposure processing.

5. Take the exposure.

6. Load the images into photoshop with 16 bit colour (to minimize the posterization in the shadows).

With this setup, since you have everything from bright sunlit elements to deep shadow, you can examine the dynamic range of the image in photoshop and determine the highlight and shadow headroom relative to the middle grey card exposure. Hopefully, the scene will have a dynamic range in shadows and highlights that is just beyond the ability of the sensors to properly render.

You could convert the image to B&W for tonal evaluation - judging photoshop numbers is easier in B&W.

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Rick Knepper, photographer, photography never for sale, check my profile for gear list and philosophy.

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