Hi all.
I'm having a bit of a problem with inconsistencies between running the Levels or Curves adjustment directly to a 16-bit grayscale image, versus doing so with an adjustment layer.
I want to be able to edit and make small cleanups to a very dark portion of a 16-bit image which is actually quite difficult to see (it's actually part of a digital elevation model, if anyone is curious). If I do the adjustment directly (via Adjustments->Levels), when I drag the sliders around... bringing the white end very close to the black, I see fairly dramatic grey level quantization as a preview, typical of if I was working with an 8-bit image. When I click OK, everything smooths itself out, thanks to the 16-bit data.
The problem is that I want to edit these dark regions (brightening them up enough to see what I am doing) but not actually affect the overall grey levels of the image. So I figure that the solution *should* be to just use an Adjustment Layer, do the same adjustment so I can visualize the changes, then when done, remove the adjustment layer and re-save. The trouble is that *most* of the time, adjusting Levels (or Curves - they behave the same) in the Adjustment Layer just visualizes the data as though it was an 8-bit image - it behaves just like the direct "Levels" command does while previewing, before I click "OK". The greyscale quantization that happens as a result is such that I can't see the details I'm looking for.
Am I doing something wrong? Is there a way to get the Adjustment Layer Levels to preview "better", using the full 16-bit image? Is there a different technique that someone might suggest to accomplish the same thing?
What makes it even stranger is that very rarely (10% of the time, and I haven't found any pattern behind it), Levels applied with an Adjustment Layer actually works properly, and the apparent 16 to 8 bit quantization in previewing the image doesn't happen.
If anyone has any idea that can shed light on this, needs more details on what I'm doing, or has any suggestions of something I can try, I've love to hear from you. Thanks!
Dan |
