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  Previous versions of RustyBug's message #11387944 « .XMP file extension? »


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Re: .XMP file extension?

Eyeball wrote:
For a 16-bit, uncompressed TIF with only one image layer, you can calculate the file size in bytes this way:

Vertical dimension in pixels * Horizontal dimension in pixels * 3 color channels * 2 bytes

For my Canon 5D2, this would be 3744*5616*3*2 = 126,157,824 bytes.

Vertical dimension in pixels * Horizontal dimension in pixels * 2 bytes * # bits recorded / 16 bits

For my Canon 5D2, this would be 3744*5616*2* 14*16 = 36796032 bytes = 35933.6 kB = 35.1 MB.

Dennis ... way cool. You know me, always diggin' the numbers.

Looks like your formula is not the same as your description ... i.e. double check the # bits recorded / 16 bits vs. "14*16". Should that be (14/16) or in the case of an 8bit camera (8/16)?

So, it sounds like the raw, while the name might suggest original really isn't the "complete" original data. It sounds like tiff is as "complete data" as is possible. So, does the tiff file data actually exist in the capture, or is the tiff file a "reverse engineer" / "reverse calculation" of the data previously consolidated from the lossless raw to produce a "complete data" tiff file?

Also, I tested the formula against my numbers and it didn't quite come up the same numbers as my tiff file size indicates @ 180MB. So I "tweaked" on the formula by changing the operator from multiply by two, to raise to the power of 2 and the my numbers came in line with 180MB for my tiff file. Whereas using the operator of multiplication is 13.5 (14MP camera) vs. 81. Is there a difference between the camera vs. PS @ how it makes such calculations?

(3000 x 4500) ^2 x (8/16)
(3000 x 4500) ^2 x 3

In either case, the dramatic size growth difference for me is the factor of 6 (.5 vs 3).
For a 14 bit camera, the "growth" factor would be 3.4 (.875 vs. 3).

Hmmm, so is the calculation for determining the number of PIXELS using the multiplication operator, while determining the number of BYTES (not to be confused with bits @ factor of 8x) uses the exponential operator.

Thanks ... this helps.

Okay ... so, my camera captures 14MP, the raw file consolidates SOME of this data and the file size varies. Tiff "unconsolidates" the data and the file size will be larger. Changing from an 8 bit to a 16 bit is an ^2 @ bytes vs. bits.

I think I've got it now ... maybe a bit crudely, but I think I'm good.


Mar 03, 2013 at 03:53 PM

  Previous versions of RustyBug's message #11387944 « .XMP file extension? »