exact colour correction?

"Peter" wrote in message

I’m working some shots and I’ve always eyeballed my color correction using levels in RGB on a channel by channel basis. I tighten the highlights and shadow arrows to the histogram also with a final tweak on the mid tones in rgb. I use the alt key and stop when I’m going to lose info on highlights or shadows. I don’t know if its me but is there a better and more exact way of doing this? I seem to have on occasion a miniscule but bothersome color cast on close inspection, it passes to the layman but for me I really need this to work. Consistency here is very important.

Hi Peter,

Your procedure is a good start. Relying on the histogram in the way you describe improves contrast, but will introduce color casts in quite a number of images.

One approach that addresses this issue is the shadow, highlight, and neutral drill, outlined in Dan Margulis’s books. If you have Windows Photoshop, and are interested in learning how to do this, consider taking the Curvemeister class, which is free and starts on the first Sunday of each month.

Many people use the Curvemeister demo for the class, and most of the techniques that I teach in the class may easily be carried over to Photoshop curves.
—
Mike Russell
www.curvemeister.com

Peter wrote:

I’m working some shots and I’ve always eyeballed my color correction using levels in RGB on a channel by channel basis. I tighten the highlights and shadow arrows to the histogram also with a final tweak on the mid tones in rgb. I use the alt key and stop when I’m going to lose info on highlights or shadows. I don’t know if its me but is there a better and more exact way of doing this? I seem to have on occasion a miniscule but bothersome color cast on close inspection, it passes to the layman but for me I really need this to work. Consistency here is very important.

Any input please.

Pete

When you say "I seem to have on occasion a minuscule, but bothersome, color cast on close inspection", do you mean the PRINT has the cast or your MONITOR image has the cast?
If your inkjet print has a cast, you can probably adjust it out by tweaking your printer driver in advanced mode.
Are you using Generic inks?
When the cast occurs, does the it occur with all papers? The more info you present the more likely you are to get a good answer. Bob Williams

The cast doesn’t appear on the monitor because I don’t want to see it, but with a print and a comparison I can see casts. When I go back to Photoshop it’s confirmed, my color correction is out. I missed it somehow. As for printing I usually correct it somemore with soft proofing. I’m using the epson r2400 and everything I use is epson, I’ve not ventured out with different papers and such.

The problem really lies in my unscientific placement of the gamma sliders in levels, I’m just eyeballing it and I feel that a more exact method is required here.

Peter
"Bob Williams" wrote in message

Peter wrote:

I’m working some shots and I’ve always eyeballed my color correction using levels in RGB on a channel by channel basis. I tighten the highlights and shadow arrows to the histogram also with a final tweak on the mid tones in rgb. I use the alt key and stop when I’m going to lose info on highlights or shadows. I don’t know if its me but is there a better and more exact way of doing this? I seem to have on occasion a miniscule but bothersome color cast on close inspection, it passes to the layman but for me I really need this to work. Consistency here is very important.

Any input please.

Pete

When you say "I seem to have on occasion a minuscule, but bothersome, color cast on close inspection", do you mean the PRINT has the cast or your MONITOR image has the cast?
If your inkjet print has a cast, you can probably adjust it out by tweaking your printer driver in advanced mode.
Are you using Generic inks?
When the cast occurs, does the it occur with all papers? The more info you present the more likely you are to get a good answer. Bob Williams

If there are true gray tones in the image, *and* if the gray tones are not supposed to have cast, then monitor the Info palette values while you color correct. In such areas, a true gray without cast should be r=g=b. But true gray areas without any intended cast often do not exist in an image. Think white sheet of paper lit but candle light.

Peter wrote:

The cast doesn’t appear on the monitor because I don’t want to see it, but with a print and a comparison I can see casts. When I go back to Photoshop it’s confirmed, my color correction is out. I missed it somehow. As for printing I usually correct it somemore with soft proofing. I’m using the epson r2400 and everything I use is epson, I’ve not ventured out with different papers and such.

The problem really lies in my unscientific placement of the gamma sliders in levels, I’m just eyeballing it and I feel that a more exact method is required here.

Peter
"Bob Williams" wrote in message

Peter wrote:

I’m working some shots and I’ve always eyeballed my color correction using levels in RGB on a channel by channel basis. I tighten the highlights and shadow arrows to the histogram also with a final tweak on the mid tones in rgb. I use the alt key and stop when I’m going to lose info on highlights or shadows. I don’t know if its me but is there a better and more exact way of doing this? I seem to have on occasion a miniscule but bothersome color cast on close inspection, it passes to the layman but for me I really need this to work. Consistency here is very important.

Any input please.

Pete

When you say "I seem to have on occasion a minuscule, but bothersome, color cast on close inspection", do you mean the PRINT has the cast or your MONITOR image has the cast?
If your inkjet print has a cast, you can probably adjust it out by tweaking your printer driver in advanced mode.
Are you using Generic inks?
When the cast occurs, does the it occur with all papers? The more info you present the more likely you are to get a good answer. Bob Williams

In article <piB6f.14678$>,
"Peter" wrote:

I’m working some shots and I’ve always eyeballed my color correction using levels in RGB on a channel by channel basis. I tighten the highlights and shadow arrows to the histogram also with a final tweak on the mid tones in rgb. I use the alt key and stop when I’m going to lose info on highlights or shadows. I don’t know if its me but is there a better and more exact way of doing this? I seem to have on occasion a miniscule but bothersome color cast on close inspection, it passes to the layman but for me I really need this to work. Consistency here is very important.

Any input please.

Use curves, not Levels, for color correction. Using Curves allows you to perform much more precise color correction.

—
Art, photography, shareware, polyamory, literature, kink: all at http://www.xeromag.com/franklin.html

I’ve read up on your posts and have done some reading thanks to your insight. As for curves, I will have to start using it, I’ve been putting it off long enough, no doubt. However because I started this latest assignment in Levels I’ll keep it for this one. What I’ve now opted to use is color correction by numbers. I’ve been picking out my highlight and shadow based on the threshold option in the adjustment menu. I use the color picker to identify these points. I then put in the readings from the info menu and add it in the levels menu. This appears to kill the cast. Now as for highlights? In rgb I slide the gamma to lighten my images (grey cloudy day). How do I know when enough is enough and when does posterization become a factor. Now the reason I ask how much is sufficient consistency is gold.

Many articles site to pick out neutral areas that are supposed to be or you think are grey, I try to avoid guessing. This seems unrealistic to me cause on many a day your monitor may be out or light in you computer darkroom may affect the visual…..

Your input is greatly appreciated

Thank You Peter
"Peter" wrote in message

I’m working some shots and I’ve always eyeballed my color correction using levels in RGB on a channel by channel basis. I tighten the highlights and shadow arrows to the histogram also with a final tweak on the mid tones in rgb. I use the alt key and stop when I’m going to lose info on highlights or shadows. I don’t know if its me but is there a better and more exact way of doing this? I seem to have on occasion a miniscule but bothersome color cast on close inspection, it passes to the layman but for me I really need this to work. Consistency here is very important.
Any input please.

Pete