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Author Topic: Color change on Photoshop 32bit to 16bit conversion?  (Read 1927 times)


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Color change on Photoshop 32bit to 16bit conversion?
« on: September 30, 2015, 01:24:36 PM »

I'm trying something new and getting a color change I don't understand. Wonder if anybody has any insight.

I'm using Photomatix to generate a 32bit HDR image from a bracketed set, then opening that image in Photoshop CC and processing it with the Camera Raw filter. All is OK to that point. But I still have a 32bit image, so I convert to 16bit with Photoshop Image/Mode.

That brings up the "HDR Toning" dialogue with "Local Adaptation" as default. I change to "Exposure and Gamma", which is supposed to be no change. However, there is a change. The resulting 16bit image has lower saturation and slightly lower contrast.

For one example, a sampler point in HSB mode goes from 23/84/16 (H/S/B) in 32bit mode to 28/65/36 in 16bit mode. It's still a useable image, but I don't understand why it changes.

The process is in ProPhoto colorspace through all steps. I feed Photomatix 16bit tifs in ProPhoto. The Photomatix 32bit HDR image is shown as untagged by Photoshop, so I assign ProPhoto when I open it in Photoshop. After opening in Photoshop, the colorspace is shown as "ProPhoto RGB (Linear RGB Profile) (32bpc)" in the Info Pallet. After the conversion to 16bit, the "Linear RGB Profile" part disappears, leaving just "ProPhoto RGB".

Anybody know what's happening with 32bit to 16bit conversion, and if it can be done without change?
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