Re: recommendation for digital camera -=> Shameless Nikon plug
From: Micha Feigin (michf_at_post.tau.ac.il)
Date: 07/21/04
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Date: Wed, 21 Jul 2004 03:40:23 +0300 To: debian-user@lists.debian.org
On Tue, Jul 20, 2004 at 05:17:54PM -0500, Alan Shutko wrote:
> Micha Feigin <michf@post.tau.ac.il> writes:
>
> > Some cameras actually compress the raw data BTW. I think Nikon does
> > that since nef (raw) output takes less space then tiff output.
>
> On some Nikon cameras they are compressed using a "visually lossless"
> algorithm. Some recent posts on the D1scussion group indicate that it
> reduces the effective bit depth from 12 bits to 9. Ick. My camera
> has a toggle to select compressed or uncompressed, but I don't
> believe the lower-end ones do.
>
> But even the uncompressed ones can be smaller than TIFFs, since they
> only log 12 bits per pixel, where the TIFFs are 8 bits per color per
> pixel. So uncompressed should be about half the size. (This is
> because each pixel is only R, G, or B straight from the CCD.)
>
Looks like you missed it a bit here. What you would call a pixel in the
raw file is not the same as a pixel in the tiff file.
In the tiff file you have three colors per pixel (R,G,B) and 8 bits per
color, that would make it 24 bits per pixel.
In the raw file you have 4 ccd cells per image pixel (R, G, G, B)
corresponding to the Bayer mask, at 12 bits per cell, which should make
that 48 bits per pixel, which in turn should make the file
approximately twice the size of the standard tiff (I think NEF files
are actually tiff files with some undocumented extensions IIRC).
The compression option probably lets you chose between lossy and
lossless compression and not uncompressed versus compressed, but its just
a wild guess.
I will have to read the code or the specs for dcraw.c (hope I got the
name right) to give you an exact answer to this.
> > There is also a plugin that allows using draw to open the raw files
> > directly in the gimp. That should rival the Nikon capture software.
>
> In terms of quality (assuming a 16bit/color gimp), yes. In terms of
> ease, no, since Nikon Capture has a lot of prepackaged actions which
> do exactly what a photographer wants to do, and the gimp doesn't. Of
> course, they could be added... 8^)
IIRC most relevant filters are already there or available, and I don't
like the magic filters of 'simple user' software anyway since it
usually doesn't do what I need (don't know Nikon Capture so I may be
way off the mark here).
>
> --
> Alan Shutko <ats@acm.org> - I am the rocks.
> Idiolocation: "You are here->" on any map.
>
>
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