Re: Color balancing images
Re: Color balancing images
- Subject: Re: Color balancing images
- From: email@hidden
- Date: Tue, 14 Nov 2006 11:16:28 +0100
The auto levels method seems to use the median as a reference, i.e.
adjust all channels to have the same median.
I've recently been trying the following 2 methods:
Method 1:
- Duplicate the image layer
- For each individual channel, select levels and adjust the gamma so
the average reads appr. 128
- Use the opacity slider to adjust between the color casted image and
the forced gray image.
Method 2:
- Convert to Lab mode
- Duplicate the image layer
- Select Filter->Average
- Invert the resulting color
- Select and delete the Lightness channel (Make L = 100%)
- Set layer mode to Multiply
- Again use the opacity slider to adjust between the color casted
image and the "filtered" image
I've been trying this because I would very much like a kind of "Color
Cast" slider in the RAW processing options as opposed to color temp
and tint. It seems a bit more user friendly to simply select the type
of lighting conditions, for example "Daylight cloudy" and then use a
"Color Cast" slider to *partially* remove the colorcast. Sometimes
the colorcast is desired, but doesn't need to be as strong as
captured etc... (sunset images come to mind or candle light/
multilight source images).
The above methods may not work for extreme corrections, but they
certainly work for "neutralizing" images were I couldn't quite find
the correct T&T.
Method 2 btw has a very interesting side effect: because the color
may be out-of-gamut, Photoshop may clip the color to white for
displaying purposes after changing to L=100. If you then multiply the
color over the image it still works even though the "filter color"
looks white. Obviously, if you would introduce alternative conversion
algorithms in the CMM, you would be able to still see a
representation of the colorfilter. For those of you who missed the
message about alternative RGB conversions, I have copied a previous
message below.
Regards,
Oscar Rysdyk
--------------------------------------------------------
Hello List members,
Due to recent developments in digital image capture and photographic
RAW file processing, discussions are emerging about the usefulness of
alternative RGB conversions in color management systems. For straight
forward matrix-based RGB conversions, current mainstream systems
mostly support Relative Colorimetric conversions only, and the
rendition of out-of-gamut values is based on simple channel clipping
algorithms.
In order to facilitate the discussion, I have been working on a
simple, bare-bones CMM for Mac OS X to demonstrate alternative RGB to
RGB conversions for matrix based profiles. Specifically the rendition
of out-of-gamut colors. The implementation includes a preference
panel which allows one to fine-tune the rendition for a particular
display or even to emulate a particular printer profile.
The files can be downloaded at:
http://www.theimagingfactory.com/download/CMSK.zip
(Again: Mac OS X only)
It's approximately 2.5 MB as it includes some test images. It also
contains a ReadMe file with some additional information and
installation instructions.
I would be interested to learn your comments, specifically about the
usefulness of alternative renditions, particularly within the realm
of photographic RAW processing, image editing in wide gamut spaces,
and/or web-publishing.
Thanks,
Oscar Rysdyk
http://www.theimagingfactory.com
--------------------------------------------------------
On Nov 14, 2006, at 05:25 AM, Roger Breton wrote:
Rich,
Roger,
Have you tried "click-balancing" for the neutrals in Curves or
Levels?
Rich Apollo
Yes, I have, and the results vary. In fairness, yes, that method works
wonder when the image presents some kind of gray-like surface.
Regards,
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
40mac.com
This email sent to email@hidden
_______________________________________________
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