Re: Digital negative ???

[Yves Gauvreau <gauvreau-yves@cgocable.ca>]

Don,

if you allow me the chance of rephrasing one of the questions below, may be
your response would be different (may be not).

Did you know that the data of an image, the numbers saved on your disk or in
memory, are transformed at least twice on its way to the face plate of your
monitor and these transform can change significantly the tonal relationship
of your images (and not the data itself)?

Regards,
Yves



----- Original Message -----
From: "Don Bryant" <dsbryant@bellsouth.net>
To: <alt-photo-process-l@usask.ca>
Sent: Saturday, December 22, 2007 1:38 PM
Subject: RE: Digital negative ???


> Yves,
>
>
> >
> And here is another question: How a CGI step tablet differ from a camera
raw
> file?
> >
>
> A camera RAW file is proprietary and may or may not be encoded in a
lossless
> format. A step tablet file is usually stored in JPG format.
>
> >
> Camera raw data as to be processed before use, see above, why not computer
> generated step tablet?
> >
>
> Because the RAW file has to be decoded to be displayed which is one of the
> primary functions of RAW processing software.
>
> >
> What's the gamma of such CGI?
> >
>
> 1 as you mentioned. It has a linear encoded space.
>
> >
> What is the white point of the CGI?
> >
>
> 0%
>
> >
> What is the colorspace of the CGI, especially colored ones?
> >
>
> What ever you assign it.
>
> >
> Did you know that the data of an image, the numbers saved on your disk or
in
> memory, are transformed at least twice on its way to the face plate of
your
> monitor?
> >
>
> Yeah, so what.
>
>
> >
> Though we know a few things about this CGI data (step tablet), like the
> relationship between levels is linear and it as an implicit encoded gamma
of
> 1,
>
>
> I repeat my question, how does this relate to your original image on the
> screen?
> >
>
> I think you have answered your own question. BTW it is possible to decode
a
> RAW file so that it has a linear encoded space as opposed to gamma encoded
> space. In some applications this is preferable but usually not.
>
> Merry Christmas,
>
> Don Bryant
>
>
>