Bit-Depth of Adjustment Layers

K
Posted By
Ken
Nov 20, 2006
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212
Replies
2
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Closed
Hello. I have a question about adjustment layers. Are they affected by the bit-depth of the document? It is my guess that they are not since the controls only offer 8-bit values to work with.

The goal is to reduce 16-bit layered files to 8-bit and save to disk using a scaled-down image. Should corrections be needed later, then the 16-bit full size image is still available (in the camera RAW format) and then the adjustment layers can be copied back from the scaled 8-bit image. I am not concerned with any issues regarding resolution or bit-depth of layer masks…

Does anyone see anyting wrong with this workflow?

Is there any documentation anywhere that states whether adjustment layers are bit-depth dependent or not?

Thanks!

Ken
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BP
Barry Pearson
Nov 21, 2006
On Nov 20, 2:40 pm, "Ken" wrote:
Hello. I have a question about adjustment layers. Are they affected by the bit-depth of the document? It is my guess that they are not since the controls only offer 8-bit values to work with.

The goal is to reduce 16-bit layered files to 8-bit and save to disk using a scaled-down image. Should corrections be needed later, then the 16-bit full size image is still available (in the camera RAW format) and then the adjustment layers can be copied back from the scaled 8-bit image. I am not concerned with any issues regarding resolution or bit-depth of layer masks…

Although you are not concerned with that, for the sake of anyone else the layer mask bit-depth appears to be the same as that of the image itself. (They can take up twice as much file space in the 16-bit case for the same number of pixels).

Does anyone see anyting wrong with this workflow?

If you are not worried about the loss of quality of the layer masks, I think this will work. I use a related method – I do ACR raw conversion at 8-bit, not 16-bit, for use in Photoshop, for efficiency. (I ran tests that showed no relevant difference for my images, as long as I get a good histogram in ACR). If I need 16-bit working later, I can reconvert at 16-bit and remake the image in the way you suggest. (However, I keep all the pixels). Needless to say, I would also need to redo any pixel-changes, such as cloning & patching! It is not something I want, or expect, to do often.

Since I create my layer masks while working in 8-bit, I am not in the position of throwing away their quality by converting from 16-bit to 8-bit, then wanting it back.

Is there any documentation anywhere that states whether adjustment layers are bit-depth dependent or not?

I haven’t seen any documentation on this, but my brief tests tell me that, when I copy adjustment layers between 8-bit and 16-bit images, I get the same values in the adjustment dialogue boxes in both images. What else matters?

—
Barry Pearson
http://www.barry.pearson.name/photography/
K
Ken
Nov 21, 2006
Barry Pearson wrote:

I haven’t seen any documentation on this, but my brief tests tell me that, when I copy adjustment layers between 8-bit and 16-bit images, I get the same values in the adjustment dialogue boxes in both images. What else matters?

I tend to agree. What matters though, regarding the documentation, is to provide a valid reason to my supervisors for suggesting a change in their workflow that they have established. I’m pretty sure I’m right, but it would help to back up my opinion with some technical data.

Ken

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