Colour Management and a new file format.... Worth a read !!

[Barry Johnston]

Here's something interesting......

Here is a blog post by the main guy working on HD Photo (a new file format) in Microsoft. The new HD Photo file format has been adopted by the JPEG committee and will eventually become JPEG-XR (probably sometime this year hopefully).

This blog post is absolutely brilliant in describing color spaces and aspects of color managment most do not know.

Although you may know this already, I just want to clarify it.

Color in software engineering and web-related content is described as RGB. Given that each color channel is 8 bits (or more easily referred to as 8bpc (bits per channel)), a typical C++ representation of a standard grey color would be:

COLORREF mycolor = RGB(128, 128, 128);

Orange would be:

COLORREF mycolor = RGB(255, 128, 0);

8 bits gives us a possible 0 - 255 value. My 1D camera captures images at 12bpc (because it uses the DIGIC II processor). 12bits gives a possible 4096 colors per channel. Canon's newer cameras use a 14 bit sensor which provides 16535 color variants of each channel.

Heres the link. Its a little long, but brilliant and worth spending the time to read it.

http://blogs.msdn.com/billcrow/archive/2007/10/25/hdr-and-color-spaces.aspx


Regards,
Barry

[Andrew Rodney]

Microsoft and color management (they still don't even color manage their darn browser or OS). Yawn. IF and when Adobe implements this, lets talk. Otherwise, its not ready for prime time.

As for the JPEG committee look at the success (not) of JPEG 2000.

He writes:

Because of these different light sources, the camera will measure different values for the red color of the apple. However, as far as we're concerned, the apple is always the same red color, regardless of the lighting conditions.

Excuse me? Its not the same color of red. What color is the apple when there's no light?

If you want a primer on scene versus output referred colorimetry (important for photographers), let me suggest this:

http://www.color.org/icc_white_paper...ent_basics.pdf

Further on:

"Adobe RGB" is a working space that provides a slightly wider gamut than sRGB, with more color spectrum that is appropriate for printers. (Remember, sRGB is defined based on the characteristics of display monitors.)

So is Adobe RGB (1998) (it was once known as SMTPE-240 in Photoshop 5 until someone told Adobe they got the chromaticity values off the web wrong). All RGB working space are based the same way and are theoretical (mathematically defined) color spaces just like sRGB!

He's got Gamma wrong (when talking about sRGB, its really a Tone Response Curve as it doesn't fallow the gamma formula). But lots of people do this (its still incorrect).

The scRGB color space and HDR/WG image formats will dramatically change the way most digital imaging is performed.

We'll see. Until its supported in Photoshop and other mainstream imaging products, its not.

[Nikolai Sklobovsky]

The HD Photo (aka jpeg XR) format is another take at the shortcomings of the jpg, I first heard of it about a year ago, or so. Backed by MS itself, no less.
However, I tend to agree with Andrew here: until it is widely supported by Web scociety (sine qua non), Windows (at least), Adobe (a must) and (preferably) the primary camera manufacturers, it's gonna be what it is now - yet another image file format.. yawn.

[Barry Johnston]

er, should that be SMPTE-240 ?

Regards,
Barry.

[Georg R. Baumann]

Barry,

can I just ask you, would you have an idea how to describe "transparent" in C++?

I think about buttons like back/forward arrows on a webpage that I would like to be transparent depending on the background, but evidently, RGB has no such value....

[Andrew Rodney]

Originally Posted by Barry Johnston

er, should that be SMPTE-240 ?

Regards,
Barry.

Actually it was SMPTE-240M!

[Barry Johnston]

I do agree with some of your views regarding Microsoft, and they may not have it fully together as far as colour management are concerned. I am in the printing and graphic arts industry where the standard of course is Mac.

Hands up those of you who own a PC, and how many of you can afford to own a Mac ? Honestly, I would prefer a Mac to PC anyday (especially as a photographer), but in Australia Mac's are unaffordable for many; and therefore, I along with 98% of the populace are stuck with PC's, and we have to make the best with what we have.

My aim at this forum is to learn from others and to help where possible. It is easy to criticize and shout down the other side, but personally, I don't care what computer you have or what car it is that you drive. If you were stuck on the side of the road, it wouldn't matter what car you were driving, I would stop to help..... this is the way I view life.

I am not here to argue or to convert people, but to try to understand how to make the best with what ever equipment it is I have.

However, I do appreciate your points of view.

Best Regards,
Barry.