I don't know a lot about bit depth, but I do know that the D 90 only takes 10 bit NEF files. Lightroom and Camera Raw open those files in a 16-bit workspace. Some of the newer cameras are taking 12 bit images, but to my knowledge no camera is taking a true 16-bit image.
Well, according to the user manual and to the review in
the D90 delivers 12-bit color depth in the .NEF files.
Of course, I haven't looked at the actual pixel data to find out how finely graded they are.
What I'm looking at is what Bridge 5.1 (WindowsXP) says about the files in the
Metadata/ Bit depth entry.
In that, the .NEF files are listed as "16-bit" depth (although it will actually hold only 12-bit resolution), but when converted to .DNG it says only "10-bit",
and that holds both when the conversion is done automatically during the importing from the camera, and when converting from .nef files afterwards.
Archiving pictures in the .dng format seems to be a good idea -- but only if no information is lost in the conversion.
Thus, the "10-bit" info showing in Bridge worries me.
Might it be that the meaning of bit depth is different in the two file formats?
Might there be something about the de-mosaicing that necessarily consumes two bits of depth? Whether in the .dng conversion -- or when saved .nef files are later to be used?
In other words, for practical purposes, are the formats equivalent in color resolution,
Or is there indeed a certain loss?
Maybe a very difficult question, but I'd sure want to have a technical ly definite answer before I dare switch to using the .DNG format all the way.
I stand corrected. I knew it was less than 16 bits. Don't know about the DNG. I guess we'll have to check the DNG specification.
Without seeing the actualy files, I would think that what's happening is that the original NEFs were in Nikon's compressed NEF format. Compressed NEFs are level compressed, and have about 10 bits of effective resolution. When converted to DNG, Adobe keeps the level compression. In that case, you're not losing anything.
As it seems to happen all too often, I have replied without thinking again. I'm using CS5, and the Bridge reports that my D90 NEF files are 16 bit. I converted one of them to DNG, and it is reported as a 10-bit file. Hopefully someone who knows will explain for us what is happening.