I would be surprised if in-camera produced TIFFs are 16 bits. They would
be extra-huge if they were. Pentax's RAW files basically *are* TIFFs (zero
padded 12->16 for the -D, and packed 12->12 for the -DS). The difference
is that only a single plane of 6megapixel, 12-bit data is necessary in RAW,
but an interpolated version for R, G, and B is needed for TIFF.
I started wondering now if you might actually store the "raw" representation
in a TIFF file, since different colour models (not just RGB) are supported,
but perhaps not quite. You can save data as luminance/crominance, but I guess
that's not exactly the same thing. And only RGB images would be considered
baseline TIFF, I think.
All a TIFF file is is a standardized format for storing bitmapped
images, as well as whatever tags you like. The thing with RAW is that
it's not a color model, it's a monochrome image. It's understood that the
monochrome image should be interpretted according to a RGBG Bayer pattern.
Only after that is done (and there are many ways to do it) can you have a
three-color-plane image. Pentax likely chose TIFF as the baseline for
their RAW format because it's an extensible, existing format. It doesn't
need much tweaking (12 vs. 16 bits for one).
Yes. I suspect that the difference would be a lot smaller with (lossless)
compression, though...
Somewhat smaller, but not much I wouldn't think. The standard
TIFF supports only a few types of compression, most of which aren't all
that great. It's similar to taking a document, copying it three times,
making small changes in each one, and then compressing the three.
Chances are it's going to be a fair bit bigger than the original
compressed.
Large tiffs may be an acceptable compromise. It's much bigger than it
needs to be, however, and does lose a slight bit of flexibility.... not
nearly so much as 8-bit gamma tiff or JPEG, though.
My point exactly. While the referenced text suggests that TIFF has no
advantages over JPEG...
The way it's typically done in-camera (8-bit, white-balanced,
gamma-corrected), it does have almost no advantages over minimally
compressed JPEGs, and the disadvantage of being much larger... usually
larger than the RAW.
-Cory
--
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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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