16 bit curves

[larkis]

When editing images in 16 bit mode within photoshop, the curve dialogue still operates on 255 steps, is there any way to make it have the fully range of steps that should go along with a 16 bit image for more precise editing ?

Also, are curves and levels applied as adjustments layers in the latest version of photoshop merged (concatenated) into one calculation when the image is flattened, or are they executed sequentially ?

I work in the visual fx/animation field as a day job and applications used for digital compositing such as shake concatenate a lot of the color correction steps a user adds in a node tree into a single lookup table to minimize any loss of values due to rounding errors.

How does photoshop handle some of this ?

[Max Penson]

To my best knowledge, photoshop uses 8 bit curves at all times with rounding. I don't know any way to edit full 16 bit data with full 16 bit LUT other than using matlab. You might want to try ACR, but I am not sure.

I am not sure how photoshop is handling multiple adjustment layers, but I am quite sure two curve adjustments will not merge into one LUT before being applied on the data.

[Jonathan Wienke]

While all of the adjustment dialogs are still limited to 256 discrete values, all of the underlying calculations are performed 16-bit-per-channel. If 256 adjustment steps isn't precise enough, you can always set the adjustment layer opacity <100%. You'll reduce the maximum amount of adjustment, but increase the precision of any adjustments. Just remember to reduce layer opacity before creating the curve.