Re: "Non-linear"?
Re: "Non-linear"?
- Subject: Re: "Non-linear"?
- From: Marco Ugolini <email@hidden>
- Date: Tue, 07 Oct 2008 15:33:38 -0700
- Thread-topic: "Non-linear"?
In a message dated 10/7/08 9:00 AM, Mo wrote:
> Hello All.
>
> Sorry for the late reply, I was out of the office for a few days.
> Thanks to those who have help clear the muddy waters.
>
> From my understanding and from what I have been told by an Adobe
> employee is that a user should work in a linear working space to
> acquire the best possible color gamut, as well as the best possible
> source color space to transform images into another color space and/or
> mode. The color space also affects Photoshops tools in their ability
> to function at maximum performance.
Mike,
I believe that there has been a terminological misunderstanding. I'm almost
certain that what the Adobe person was referring to were working spaces that
are *visually linear*, as well as *perceptually uniform*.
"Visually linear" means that equal steps in the color space are perceived as
equal steps by the human observer. "Perceptually uniform" means that an
equal amount of change in a color space (in lightness, for example) is
*perceived* as equal regardless of where it takes place within the confines
of that color space.
But in no way does this mean that the working space must have a linear
*gamma* (also called "Tonal Response Curve", or TRC). Visually linear is not
equal to gamma-linear (TRC = 1.0). As a matter of fact, human vision is far
from linear, and instead functions more along a logarithmic curve. (The L*
in Lab is an attempt to model the way human visual perception works, and is
not very far from gamma 2.2.)
> I think if we replace the term "linear" with "uniform" it makes far
> better sense in what I was trying to describe and it was not my
> intention to provide disinformation to the original inquiry.
I think I understand what you meant now. :-)
> So I guess I should pose a question to the forum. Is Adobe RGB a
> better color space then sRGB? If not, then why did Adobe create it
> for it's applications?
"Better" is not applicable. What is "better" in a given instance depends on
how the image was created and which is its intended use.
AdobeRGB is a larger color space than sRGB. But that does not make it
"better" in an absolute sense.
If your work is limited to output for the World-Wide Web, sRGB is very
likely all you need.
But if you work in the print world, AdobeRGB is a "better" space, since sRGB
does not encompass a sizable portion of colors that exist in quite a few
standard CMYK print spaces (SWOP, sheetfed, etc.).
And if you are a fine-art photographer, you may want to consider an even
larger working space, such as ProPhoto RGB, or DonRGB.
Marco Ugolini
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