What is advantage of saving RAW image vs. just saving Tiff

Since RAW images can't be used until converted to Tiff or some other sort of file, what is the advantage of saving the RAW file? Also what is the advantage of converting a RAW file to a 16bit vs an 8 bit Tiff. PS can't use the magic wand on a 16 bit file and so I have to convert it to 8 bit in order to selectively sharpen.
Do you print Tiff files at 16 or 8 bits?
That's three different, but related questions isn't it?

There are a number of questions embedded here that I'll try to address:

- TIFF file vs RAW file: The RAW file is much smaller and is what the camera initially captured. The TIFF file or PSD file, which I prefer since it saves layers and is a bit smaller, is what I save for an image after I have processed it so that I don't need to reprocess the file at a future time. If that is good enough for you, saving that one is probably all you need. I personally prefer keeping the original RAW file though too because the RAW converters are getting better and who knows what capabilities we will have for RAW file processing in the future. For example, Capture One or Adobe RAW offer some capabilities that were not previously possible on other RAW converters. Had I not kept the RAW file, those images would not have received the benefit of those new programs.

- Converting to 16 bit vs 8 bit. If your digital capture is being done in 16 bit mode in the camera (really 12 bit but in a 16 bit data word), conversion to 8 bit deletes some information and reduces the number of colors available by 6 orders of magnitude. In most cases this doesn't matter since our eyes can't see that many colors. But when you have an image with a tonal graduation within the same color - you only have 256 graduations available - this can look banded. Having 65,000 tones of the same color as you would in a true 16 bit color scale would not show this banding. There is tonal degradation when making the shift.

- Tools in PS not working in 16 bit mode. The preferred worflow is to do as much work in 16 bit mode and then converting to 8 bit mode to finish the job. So you would do levels work and curves work in 16 bit mode and then convert to 8 bit mode for use with tools that only work in 8 bit mode. This remaps the colors much more naturally and reduces the chance of banding. As a test, take an image in 16 bit mode and do a significant levels adjustment then look at its histogram - it looks like a comb - everywhere where the data drops off is lost data. Now do the same thing in 16 bit mode and notice there is very little of this combing effect.

- Selective processing in 16 bit mode. As you said the magic wand doesn't work in 16 bit mode but there are other ways that you can sometimes make the selection. Both the rectangle marquis and the oval marquis work in 16 bit mode so you can select sections of your photo with those and then apply selective levels and curves.

- Printing - convert the image to 8 bit because the printer will do it for you anyway and I would much rather see what I'm printing than have the printer surprise me.

A final note, converting an image from 8 bit to 16 bit for color adjustment, levels adjustment, or curves adjustment is not useful you can't create data that no longer exists.

Hope this helps.

Thanks E.J. for the very clear explanation.
Does the 10d capture in 12bit(16bit)?

RichardMittleman/Gon2Foto wrote:Does the 10d capture in 12bit(16bit)?

In RAW mode, yes it does - can't remember off the top of my head whether or not you have to set-the camera up that way or if its that way by default.