Converting an 8-to 16-bit grayscale before adjusting ?

[Sasquatchian]

"and just couldn't figure out how to convert the image to a more lossless bit-depth. "

Lossless bit depth? Makes no sense. Any tonal manipulations you do are going to result in data loss, no matter what. It's whether or not the manipulations make it a better image or not that matter, not the state of the histogram.

[Leigh]

just couldn't figure out how to convert the image to a more lossless bit-depth.

Ken,

You have not "lost" anything. Neither have you added anything.

Set an egg on the counter. It's an egg.
Put the egg in an empty carton for a dozen eggs.
It's still an egg, with 11 adjacent empty holes.

That's what happens when you increase bit depth.
It's not like you're copying the information from one pixel into the new adjacent pixels.
The new adjacent pixels are empty, which is why they show up as empty in the histogram.

I'm afraid you're obsessing over an imaginary issue.

- Leigh

[bob carnie]

Nice explanation

What would be your description of the egg if you had a 16 bit file and dropped to 8 bit.

Ken,

You have not "lost" anything. Neither have you added anything.

Set an egg on the counter. It's an egg.
Put the egg in an empty carton for a dozen eggs.
It's still an egg, with 11 adjacent empty holes.

That's what happens when you increase bit depth.
It's not like you're copying the information from one pixel into the new adjacent pixels.
The new adjacent pixels are empty, which is why they show up as empty in the histogram.

I'm afraid you're obsessing over an imaginary issue.

- Leigh

[Peter De Smidt]

Likely less eggs.

[Ken Lee]

Apparently when the image is re-sized, Photoshop inserts intermediate values according to the bit-depth. Subsequent adjustments are made in the new bit-depth.

Some of the values in the new file come from the original 8 bit data and the rest are produced by interpolation and/or the scaling algorithm.

Whoever wrote or maintains the code will know best.

[RSalles]

Ken,

Pay attention to the first image. No matter what the histogram shows, the image with much more detail still is the first 8bit one.
I think the PS gap filling alternative is another kind of a guess, reminds me a filling of a bayer filter with their adjacent probabilities.
Look inside the shoes, there are details not visible in any other sample,

Cheers,

Renato

[Ken Lee]

Ken,

Pay attention to the first image. No matter what the histogram shows, the image with much more detail still is the first 8bit one.
I think the PS gap filling alternative is another kind of a guess, reminds me a filling of a bayer filter with their adjacent probabilities.
Look inside the shoes, there are details not visible in any other sample,

Cheers,

Renato

Sorry for any confusion. The first image is the original, the rest have had multiple random adjustments to the tonal curve.

[Leigh]

Apparently when the image is re-sized, Photoshop inserts intermediate values according to the bit-depth. Subsequent adjustments are made in the new bit-depth.
Some of the values in the new file come from the original 8 bit data and the rest are produced by interpolation and/or the scaling algorithm.

Correct.

Envision two adjacent pixels in the original 8-bit file, one white and one black.
Translated to 16-bits, you have one white pixel and one black pixel separated by 254 empty ones.

Re-sampling may fill in those 254 empty spaces with shades of gray, yielding a smooth gray scale.
OR
It might make half of them closest to white all white and the others all black.

It depends on the algorithm and the settings in use.

- Leigh

[RSalles]

Ken,
Even have been driven to error, I'm glad I've noted the difference, at least my eyes are not that bad, until now - I'm 58 y.o. today.

Leigh,

Correct, but in the original 16 bit image those 254 empty ones are filled with data. No PS can "invent" data do fill those gaps, only smooth transitions. That's why one have - if possible - start with the max amount of bits available and adapt the final output to the max. supported by the medium - example not loosing time to try to display 16 bits images on the web.
The thread reminds me another one about max lens resolution and MTF charts, all that ending with a photo displayed on Flickr,


Cheers,

Renato

[Leigh]

Correct, but in the original 16 bit image those 254 empty ones are filled with data.
No PS can "invent" data [t]o fill those gaps, only smooth transitions.

It depends on the scene, the image, and the software.

A smooth transition from white to black (inventing a gray scale) might be valid in some cases.

If the original subject has an abrupt change in color, like a paint line, a transition would degrade the image.

There are no universal truths.

- Leigh