U of S | Mailing List Archive | alt-photo-process-l | Re: Digital negative ???

Re: Digital negative ???

Here is a bit of text from Adobe:

The Pros and Cons of Raw Data
Seeking a greater degree of flexibility and artistic control, professional
increasingly opt to manipulate raw data from their digital cameras. Unlike
formats which store images that have been processed by the camera, camera
raw files capture
unprocessed or minimally processed data directly from the camera sensor.
Because they are
analogous to film negatives in a photographer's workflow, camera raw formats
are often
referred to as "digital negatives."
Camera raw formats offer both advantages and disadvantages. One advantage is
artistic control for the end user. The user can precisely adjust a range of
parameters, including
white balance, tone mapping, noise reduction, sharpening and others, to
achieve a desired
One disadvantage is that unlike JPEG and TIFF files which are ready for
immediate use,
camera raw files must be processed before they can be used, typically
through software
provided by the camera manufacturer"

And here is another question: How a CGI step tablet differ from a camera raw
Camera raw data as to be processed before use, see above, why not computer
generated step tablet?

What's the gamma of such CGI?

What is the white point of the CGI?

What is the colorspace of the CGI, especially colored ones?

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

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

Happy Holidays

----- Original Message -----
From: "Yves Gauvreau" <gauvreau-yves@cgocable.ca>
To: <alt-photo-process-l@usask.ca>
Sent: Saturday, December 22, 2007 3:02 AM
Subject: Digital negative ???

> Hi,
> from the various text available on the net it would seem that most
> use a computer generated (CGI) step tablet in orther to create the proper
> negative for the desired process. My question is, how does this CGI relate
> to the image on the monitor?
> Happy Holidays
> Yves