16 bit in Photoshop, it's fake?

[Zequim]

Hello friends, there is something that has been confusing my mind.

When I create a 16-bit file in Photoshop, all the color and light adjustments continue to act with just 256 passes.

If I create an 8-bit file of 256x256 pixels and pass a white to black gradient I can measure each pixel with its specific depth.

But if I create a 16-bit file with 1000x1000 pixels and pass the gradient from white to black, it's impossible to measure the colors, since all tools continue to work at 256 levels only.

Is there any explanation for this?

[TheDigitalDog]

Actually, it's 15 bits plus one level...done for algorithmic processing reasons. And since there really isn't a real life source of full 16 bit images, that's all the precision Photoshop needs.

There are more 'bits' of data doing this, set your Info palette to show you this. 

[Zequim]

Hi friend, I didn't really notice that I could set my info window to 16 bits I'm sorry.

With that resolved.

I would still like to know if I can make the color tools, color picker, or levels tools work 16 bits deep?

[Zequim]

[D Fosse]

That's just the readout. The tools work in 16 bit depth on the data.

[Zequim]

Yes, that's what I imagined.

A 65k level adjustment would be weird.

[TheDigitalDog]

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@Zequim wrote:

I would still like to know if I can make the color tools, color picker, or levels tools work 16 bits deep?

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Yes, most (but not all, some filters for example) work on the high bit data. 

http://digitaldog.net/files/TheHighBitdepthDebate.pdf

[Zequim]

Thanks a lot my brother, I'll take a look.

[D Fosse]

Correct about the filters - but you spot those immediately, because they simply don't work if the file is 16 bit. They are just grayed out in the menu.