Unfortunately, it's going to be very difficult to diagnose your problem without having the psd file for this image in front of us. Without it, the discussion will just be little more than one guess after another.
Here's a possible way around this: Since the old psd file is in storage, can you reproduce the problem with a new image and then send us that psd file?
With respect to this image, here are some of my observations:
1. It looks identical whether I view it in PS, Windows Photo Viewer, XnView, Firefox, or Irfanview. BTW, don't use the little preview version generated for in-line display in the forum thread for evaluation -- instead, drill down till you get to the original. I should point out that I have done my own tests on the forum image uploading software and find that after you drill down by clicking on the forum image several times, the final image you retrieve is bit-for-bit identical to the image that one uploaded, so there is no problem with data modification by the forum software, as long as you don't rely on the little in-line preview image.
2. I see only extremely minor posterization in the overall image. In addition, I separately examined the R, G, B channels, as well as H, S, and L channels that I generated from your image. They also looked fine.
3. The only way I could make the minor posterization visible was to use a local contrast enhancing technique that wildly exaggerates it. The 1st attached image shows the result of this.
To give you a sense of what you are seeing, next, I intentionally posterized your image to 26 levels and then applied the same visualization technique to the version I intentionally posterized. As you can see, the extra posterization is plainly visible.
Without the artifact enhancement technique, even the intentionally added posterization would hardly be noticed by most viewers.
4. As you can see, the areas in which I found the most obvious (but minor) posterization (eg, the cheeks and forehead) are not the same areas that concern you. It is widely known that posterization is usually only a problem in broad areas of smoothly varying color / brightness. It is rarely a problem in highly detailed areas like hair or edges, the areas of concern to you. Is it possible you are seeing some other artifact and calling it "posterization"? I examined those areas for other artifacts such as sharpening halos and "stair-stepping". Any significant JPG compression artifacts would have shown up immediately with my local contrast enhancing technique. To be honest, I didn't see any artifacts of significance.
So, at this point, unfortunately, I really don't know what to tell you. IMHO, other than being a bit more heavily saturated and maybe softened a bit more than I prefer, IMHO, it looks like a very reasonable image, and I'm not know for soft-pedaling technical criticism.
Perhaps, as I suggested above, you can force the effect on a new image and we can figure out what's going on using that?
Sincerely,
Tom M
