I am looking to get my old c-41 35mm negatives scanned and most labs are providing 8 Bit TIFF only. Some people say that there is more posterisation effects while working with 8 bit mode so it benifits to work on 16 Bit TIFFs.
But I have also researched that we can also work on 8 Bit TIFF with 16 bit mode on photoshop to prevent posterisation. So I am thinking what are the benifits of TIFF originally scanned at 16 Bits?
And if there are benifits like for example more “original” color depth data, are they really worth it?
“Beauty is in the eye of the beholder”… and value is a highly subjective matter too.
I propose that you test it yourself, having a film scanned with 16 bit/colour, save the 16 bit files as 8 bit files and apply the same processing. If Differences exist, they should appear in such a test.
You could also go the other way 'round, saving 8 bit tiffs as 16 bit tiffs and apply the same processing.
There’s no testing needed. Yes, there are benefits in scanning at 16 bits and it is worth it if you want to post-process the resulting files to any significant degree. An 8-bit file can use 256 distinct tones to represent a colour at each pixel position. A 16-bit file can represent 65,536 values. So, if you are going to edit the files to any significant extent, do the math. An 8-bit image will be a lot more prone to banding or posterisation when edited especially in areas of smooth tone whereas a 16-bit image can be extensively edited with no discernible degradation. However, once the editing is completed (either by the lab or by you) and you are sure you won’t be changing your mind, you can save in 8 bits which is fine for both display and print. If your lab only supplies 8-bit files I wouldn’t worry too much - they will resist a modest amount of post-processing without any visible deterioration.
To answer your second question, yes you can convert an 8-bit image to 16-bit but there is no advantage. All you get is an 8-bit to 16-bit conversion. The underlying colour data has not changed at all but you will have doubled the file size! There is a theoretical advantage of having some of the work done in 16-bits, but that all gets lost again if you convert back to 8-bit.