Re: Understanding color balancing
Re: Understanding color balancing
- Subject: Re: Understanding color balancing
- From: Dan Reid <email@hidden>
- Date: 20 Dec 2005 08:22:41 -0800
- Date: Tue, 20 Dec 2005 09:19:40 -0700
on 12/19/05 3:25 PM, Lars Vinberg at email@hidden wrote:
> A short intro about myself since I am new to posting on this list: I am a
> landscape photographer, work with film up to 8x10 as well as digital. I am
> also a software engineer.
>
> I am trying to figure out how to make a color balancing tool for correcting
> color balance in photographs. Ideally the user should be able to use a
> dropper tool to click in neutral hightlights, midtones, and shadows,
> possibly even more points. The tool should then make a correction of color
> balance for the luminance where clicked. Possibly a UI similar to Photoshop
> or Aperture.
>
> My question is: What is the proper way to do this, mathematically? The
> working color space is an RGB space. My guts tell me that adjustments should
> be made in chrominance only, keeping luminance fixed. Adjusting RGB curves
> directly is of course a no-no. I could do corrections in Lab space but
> calculations get a bit expensive. Is there a better way?
>
> I admit that this question is a bit vague, but to more precisely formulate
> my question I think I need more information or understanding of how to
> mathematically do chrominance corrections.
>
You can do this easily in Photoshop if I understand your question correctly.
Photoshop levels will do this task easily (actually curves too). Simple open
the levels or curves window. Double click on the highlight eye dropper, this
will open the Photoshop Color picker. Now click on the image highlight area
you want to adjust. This will sample the color. Now adjust the saturation of
HSB to remove chroma while preserving hue and lightness. Click ok to accept
the color picker change. Now click again with the highlight dropper and see
Photoshop automatically remove color saturation without messing with
lightness or hue. It figures out the RGB number for you like a sophisticated
color calculator. Pretty cool, no?
Same process for gray and black eye droppers if you need to adjust those
areas as well. If you need to skew the color balance you can always adjust
the hue angle to get better match if needed.
No long-winded explanation here just a simple resolution. Geez.
--
Dan B. Reid
RPImaging
Color Management Products & Training for Print, Internet, & Motion Graphics
http://www.rpimaging.com | Toll Free: (866) RGB-CMYK
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden