Curves – Individual Channels

John, thanks for your reply. I think perhaps you are spot on with the extra tweaking suggestion my notes were quite brief and my memory has failed me on the detail.

We did not touch on LAB mode much so not sure under what circumstances its preferrable to use it. I will have to research some more. In fact its about time I invested in some books on the topic as you (and others) have suggested to me.
I gues I’ve been a bit "shy" of using layer upon layer (not sure why) but it seems th emorte I read this is the name of the game.
Thanks again.
"John T" wrote in message

These are my views on your question. I’m still a learner.
In deference to the people who ran the course you attended, I suggest that perhaps what they really recommended was that after adjusting the individual channels, the image might sometimes be further improved by a little extra tweaking of the composite RGB or CMYK channel, perhaps to increase overall contrast and so on. But you have to be have to be the judge of this. Don’t forget CIE Lab mode. PS has 10 channels and all can be used to improve an image.

You’re well on the right track as regards using adjustment layers, but you are way off base in looking for "an easier way." It only takes a mouse click to create an adjustment layer. That’s not too hard, and it gives you the ability to revise your adjustments whenever you wish.
I recommend you study a book such as "Professional Photoshop" by Steve Margulis.

http://www.amazon.com/exec/obidos/ASIN/0764536958/qid=105922 4386/sr=2-1/ref=sr_2_1/104-5152271-4935905

The book is in its 4th Edition, and the author claims that he is still a learner.

Another good book is "Photoshop Color Correction" by Michael Kieran.

http://www.amazon.com/exec/obidos/tg/detail/-/0321124014/ref =pd_bxgy_text_1/104-5152271-4935905?v=glance&s=books&amp ;st=*

On Sat, 26 Jul 2003 02:01:30 GMT, "Peter Detheridge" wrote:

I once did a PS scanning course where it was recommended to colour

correct

the individual channels first and then do the final editing on the combination of RGB (or CMYK depending on the mode you are in). Trouble is, I do not see how to do this. Easy I hear you say….use the

Red

Channel /Green Channel and Blue channels from drop down list and do the usual highlights and shadows etc. All good until I try to do this for

RGB

together which then overrides the changes I just made to the channels individually.

Other than making a new adjustment layer per channel plus one for RGB,

is

there an easier way to do this?

"John T" wrote in message

…
I recommend you study a book such as "Professional Photoshop" by Steve Margulis.

http://www.amazon.com/exec/obidos/ASIN/0764536958/qid=105922 4386/sr=2-1/ref=sr_2_1/104-5152271-4935905

*Dan* Margulis. Excellent book.

I’ve just ordered a copy from Amazon!!

"Warren Sarle" wrote in message

"John T" wrote in message

…
I recommend you study a book such as "Professional Photoshop" by Steve Margulis.

http://www.amazon.com/exec/obidos/ASIN/0764536958/qid=105922 4386/sr=2-1/ref=sr_2_1/104-5152271-4935905

*Dan* Margulis. Excellent book.

On Sun, 27 Jul 2003 00:34:55 GMT, "Warren Sarle" wrote:

"John T" wrote in message

…
I recommend you study a book such as "Professional Photoshop" by Steve Margulis.

http://www.amazon.com/exec/obidos/ASIN/0764536958/qid=105922 4386/sr=2-1/ref=sr_2_1/104-5152271-4935905

*Dan* Margulis. Excellent book.

Thanks for the correction, Warren. I’ve got no idea where the "Steve" came from, and I’m embarrassed that I checked the name of the author only a few minutes before I wrote it in the email.

Thanks Mike,
I am sure I have adjusted the end-points in the separate channels with the eye droppers and then done "final adjustment" using the eye droppers for the end points of the composite, only to see the curves change in the individual channels.

Regardless, I intend to take your advice (again:-)) and only make overall contrast/brightness changes in the composite.

Peter
"Mike Russell" wrote in message

Peter Detheridge wrote:

I once did a PS scanning course where it was recommended to colour correct the individual channels first and then do the final editing on the combination of RGB (or CMYK depending on the mode you are in). Trouble is, I do not see how to do this. Easy I hear you say….use the Red Channel /Green Channel and Blue channels from drop down list and do the usual highlights and shadows etc. All good until I try to do this for RGB together which then overrides the changes I just made to the channels individually.

Other than making a new adjustment layer per channel plus one for RGB, is there an easier way to do this?

I’m not sure I understand what you mean. Adjusting the RGB "Master" curve does not change the adjustments to the individual channels.
If you mean changing the master curve alters the final RGB values, and/or adds a cast to the imagethat’s what’s its there for.

Better still to not use the RGB curve at all for the endpoints. If anythikng, us it only for subtle changes to overall brightness. You can

do

everything you need using the individual channels.

—

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Peter Detheridge wrote:

Thanks Mike,
I am sure I have adjusted the end-points in the separate channels with the eye droppers and then done "final adjustment" using the eye droppers for the end points of the composite, only to see the curves change in the individual channels.

I’ve found that the eyedroppers generally don’t work well. They will indeed adjust all three channels rather brutally, forcing your highlights and blacks to neutral white, which is often the wrong thing to do because more often than not it adds a color cast, which none of us wants.

Try applying the same curve as an adjustment layer in luminance mode and you’ll get a more natural result. Or if you want to take the trouble of convertint to Lab mode you can have separate control over your brightness and color saturation.

Regardless, I intend to take your advice (again:-)) and only make overall contrast/brightness changes in the composite.

The best use of curves is to use the individual RGB channels to correct overall color casts and adjust the shadow, highlight, and overall brightness simultaneously, without resorting to the master curve at all.

This is how Margulis does it, and it is extremely effective.

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net