Re: recommendation for digital camera -=> Shameless Nikon plug
On Tue, Jul 20, 2004 at 08:53:23PM -0500, Alan Shutko wrote:
> Micha Feigin <michf@post.tau.ac.il> writes:
>
> > 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.
>
> Actually, it's close enough.
>
> > In the raw file you have 4 ccd cells per image pixel (R, G, G, B)
>
> That's not correct for any Bayer camera I know of. Specifically not
> correct for the Nikon DSLRs or consumer cameras.
>
> There's one CCD cell per image pixel, with the exception of the D1x,
> which has a strange layout[1].
>
There is no way that this can be true physically.
CCD (and CMOS) cells are sensitive to intensity only, they have no color
sensitivity.
They have a color (usually Beyer) mask put over them so that each cell
receives only red, green or blue light. Each four cells are divided into
one red, one blue and two green (this is since the human eye has better
separation for green and square grids are easier to design).
The only thing strange about the D1x is the double resolution on the
horizontal axis which is then interpolated into higher resolution on
the vertical axis. Other then that the color filter is standard.
This is different from how modern film works where the colors are
layered.
As a side note, what could be interesting is if you could disable or
remove the color mask to get 4 times the resolution on B/W pictures.
> > 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).
>
> Correct, NEF files use a TIFF container.
>
> As for sizes, TIFFs from the camera really are about twice the size
> of uncompressed RAW.[2] If you really want, I can provide pics taken
> in each mode.
>
That could be interesting, but wouldn't tell me anything. I need to
look at the code that converts them to see what it does.
> > The compression option probably lets you chose between lossy and
> > lossless compression and not uncompressed versus compressed, but its just
> > a wild guess.
>
> The D1x allows a choice between uncompressed and compressed[2]. The
> D70 does not.[3] Neither allow you to choose lossiness. The above
> link explains the loss of detail.
>
> (You're guessing. I've got the camera.)
>
I just don't see what would explain the sizes, unless the camera is
dropping information or storing extra information in the tiff, or just
packs it badly in the tiff.
I don't have the time to look into it at the moment through.
> > 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.
>
> See [3], where they did. There's also more info in the D1scussion
> archive[4] which is unfortunately available only to members.
>
> > 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).
>
> Yep, you're way off.
>
> For example, NC offers:
>
> * Autoremoval of sensor dust from images, given a reference.
>
> * Fisheye-to-rectilinear with some lenses.
>
> * Vignette control, to increase or decrease vignetting. It knows the
> properties of the lens you used. Very cool.
>
> * Lets you adjust exposure by standard EV values
>
> * Easy highlight/shadow adjustments. Really, really easy.[5]
>
Sounds interesting.
> Now, you _can_ do all of this with the gimp. But it's a more manual
> work. NC lets you work on thumbnails, set image settings, then batch
> convert. And you're limited in your plugin choice because you have to
> use filmgimp to get 16-bit color, to take full advantage of the extra
> range in the files. Or, use the RawPhoto plugin and fiddle with
> settings before actually converting it into 8-bit per channel, but
> then you're severely limited in your available modifications.[6]
>
> Footnotes:
> [1] http://www.dpreview.com/reviews/nikond1x/
>
> [2] http://www.dpreview.com/reviews/nikond1x/page15.asp
>
> [3] http://www.majid.info/mylos/weblog/2004/05/02-1.html
>
> [4] http://www.juergenspecht.com/d1scussion/#13
>
> [5] http://www.lonestardigital.com/digital_dee.htm
>
> [6] http://ptj.rozeta.com.pl/Soft/RawPhoto
>
> --
> Alan Shutko <ats@acm.org> - I am the rocks.
>
>
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