Photoshop Channel concepts: The Power of Ten

[wallykid]

Hi Michael,

As promised I'll leave you in peace now. Your posts have been very helpful. I really do appreciate the time you took to answer my questions. I owe you a beer or two!

Take care,

Conor

[Graphics23]

Originally Posted by Richard_Lynch

Michael,
I don't know about pushing off someone to Dan's book as that was a pretty good primer.

Thank you!

I always recommend Dan to anyone serious about image editing. In the prepress world, Dan is the Man!

I use sRGB almost exclusively (largely because of tests in my workflow) and am glad to see you downplay the importance of color space -- too many, I think get riveted to an idea they've heard. Pre-press people don't have that advantage, as they have to deal with reality ;-).

Yes, indeed! I deal with far too many "Artists" who get hung up on their precious colors. If they only knew what I do to their files prior to output...

In the last five years I can recall loosing only one job due to not being able to sufficiently match color, and that was because the "Artist" wouldn't supply me with hardcopy to see what I was supposed to match!

Probably the best thing that ever happened for me having to do with imaging was getting thrown under the pre-press train when I worked for a photography book publisher as a jack of all trades...including layout, color correction, and editing. It was a fabulous way to learn all about digital rendering.

I've said many, many times that spending a year as an entry level prepress technician is an invaluable education for someone looking to work in any aspect of the graphics industry.

One major peeve of mine is that college level graphics courses don't really prepare the student to work in the real world. Too much emphasis is placed on having a pretty portfolio and not enough on production.

I am curious as to your position stated:
That may confuse some people as Adobe clearly uses profiles as names for working color spaces. I think I know what you mean, but would you care to clarify?

As used by Adobe, the term "working space" refers to an application level setting which determines the default ICC Profile for RGB and CMYK documents. This default profile, or "working space", is used whenever one changes color mode via the Image>Mode menu commands. It is also the assumed profile when one opens any document which does not already have an embedded ICC Profile. Even, confusingly enough, when one chooses "Leave as is (don't color manage)" in the Missing Profile dialog or "Discard the embedded profile (don't color manage)" in the Embedded Profile Mismatch dialog.

I took exception to the term "working space" as used by the original poster, because it implies that one is changing the application level color settings on a per document basis, a practice I don't recommend. Converting your Adobe RGB image to sRGB for posting to the web is not the same as changing the "working space".

I'm nitpicking, certainly. But I always make it a point to use the terminology as precisely as possible when explaining these rather complicated subjects.

Now how about elaborating on that channels as layers topic?

Regards,

Michael

[dahved]

I read your Powers of Ten, and this thread, and I say "Thanks!" for all the great info.
I'm wondering what you meant when you wrote about a quick blend of the A into the L using Overlay mode. What steps did you take to do that? (I understand that it was in LAB mode, but I don't get how you overlaid a channel on another.)

<<<For example, the other day I was working on an image where I wanted to increase the contrast between subject and background. After running the Ten Channel Action I noticed that in the A channel of LAB the subject was light and the background dark. After a quick blend of the A into the L using Overlay mode I got just what I was looking for.>>>

David

[Graphics23]

Originally Posted by dahved

I read your Powers of Ten, and this thread, and I say "Thanks!" for all the great info.

You're welcome!

I'm wondering what you meant when you wrote about a quick blend of the A into the L using Overlay mode. What steps did you take to do that? (I understand that it was in LAB mode, but I don't get how you overlaid a channel on another.)

I almost always use the Apply Image command when doing channels blends. One may also use Channel Mixer and Calculations, but I tend to use those more for creating masks.

Here are the steps:

Open the channels palette and convert to LAB.
Duplicate the background layer.
Click on the L channel. Then hit the tilde key (~) to view the composite so you can see the results.
Go to Image>Apply Image.
The "Source" will be the image you're working on.
Set "Layer" to Background.
Set "Channel" to A.
The "Target" is always the active channel(s) and layer of the working image.
Set "Blending" to "Overlay".
Set "Opacity" to 100%.
Click "OK".

ApplyImageScreenShot.jpg

Here's the results of the actual image I was referring to:

Before

tiger-before.jpg

After

tiger-after.jpg

Regards,

Michael

[Michel B]

Trying to replicate this Lab correction in Elements with Benny Pedersen's Lab add-on:
- Extracting A channel in a duplicate file
- add a luminosity layer on original, ie duplicating background, new 50% gray layer under duplicate. Duplicate set to luminosity, merge down, set mode to luminosity
- copy A channel from duplicate file to new layer, link to luminosity layer and mode to overlay.

The result was not enough, so I duplicated the A layer and did minimal colour and levels adjustments.

Thanks for this tutorial (and to Benny Pedersen...)

Michel B

[Graphics23]

Well done, Michel B!

Regards,

Michael

[ratherbsouth]

Hi Michael,

Wow... I thought I knew something about photoshop and digital imaging until I found this site and especially your posts. I've been using photoshop since version 2, but now I realize just how much I still need to learn. I'm very interested in your solution to the high contrast image (the backlit christmas scene) and custom ICC profiles. I had no idea that this type of adjustment could be done just by assigning a new profile. I would like to learn more about creating and using custom profiles. Is there a book or website that you recommend that covers this subject? Is there a website where I could download custom ICC profiles, like there is for actions, etc.

Thanks for your time!
Andy

[sonny7]

Pirate,

GREAT, I have been a user of the technique of using LAB channels to find an alternative means to an end. Found your action to be very useful. Great insight. Thanks
Richard

[dahved]

Michael,

Thanks for the step-by-step help...I still need lots of practice to figure out what corrections any particular photo would need...

[Graphics23]

Originally Posted by ratherbsouth

Hi Michael,

Wow... I thought I knew something about photoshop and digital imaging until I found this site and especially your posts. I've been using photoshop since version 2, but now I realize just how much I still need to learn. I'm very interested in your solution to the high contrast image (the backlit christmas scene) and custom ICC profiles. I had no idea that this type of adjustment could be done just by assigning a new profile. I would like to learn more about creating and using custom profiles. Is there a book or website that you recommend that covers this subject? Is there a website where I could download custom ICC profiles, like there is for actions, etc.

Thanks for your time!
Andy

Hi Andy,

Welcome to RetouchPRO!

Thanks for the comments.

I can't say that I've been using Photoshop since version 2, but I could probably get my hands on a copy of version 3 if I go digging around in my attic.

I can't take credit for the idea of using custom ICC profiles. I got the technique from reading Professional Photoshop by Dan Margulis.

I don't know of any specific websites on this topic, but Dan has a newsgroup over at Yahoo, and there's a discussion of his work over at Digital Grin where I volunteered to do the chapter summary on ICC profiles. It's still in the works, I got promoted to management a little while ago and have been quite busy lately, but when finished I'll very likely post an edited version here at RetouchPRO.

It certainly is a powerful technique, and as stated previously I use variations on it quite often. Dan's book shows how to create the custom ICC profiles used in his examples and provides them on the companion CD.

Regards,

Michael

[Graphics23]

Originally Posted by sonny7

Pirate,

Arrrr...

That be Cap'n to you, ye swob!

Arrrr...

GREAT, I have been a user of the technique of using LAB channels to find an alternative means to an end. Found your action to be very useful. Great insight. Thanks
Richard

Hi Richard, welcome to RetouchPRO!

I'm glad you find the action useful and thanks for the comments,

Regards,

Michael

[Graphics23]

Originally Posted by dahved

Michael,

Thanks for the step-by-step help...I still need lots of practice to figure out what corrections any particular photo would need...

You're welcome!

There's the rub. All the fancy technique means nothing if you don't know when and why to apply it.

I'm very much in that boat myself. Working in the print industry, I have an eye for print, so I know when and why to fix images so they look good on paper. But I don't really have a "retoucher's eye". Which means I don't immediately see the things that are required to make an image of a model's face ready for a high-end fashion magazine.

This thread is a good example. I looked at the image and thought, "That should print well, what more does it need?" But the retouchers see a myriad of issues which need correcting.

So not only do you have to learn how to use Photoshop, you also have to learn why to use it.

But that's what makes it so much fun!

Regards,

Michael

[Stroker]

You are not limited to the 10 channels in the Channels palette. It is most definitely a good start, but there is more. If you know the different colour spaces, blending modes, and ChOps, then you can extract even more channels.

Attached is an example of the pure hue channel and saturation channel (HsY). Both of these done with stock tools.

(I borrowed the tiger - I hope you don't mind.)

[Graphics23]

Nice one, Stroker!

I keep the old HSB/HSL plugin around to extract Hue and Saturation channels.

Giving me, in essence, a total of 14 channels!

But the "B" of HSB, the "L" of HSL, and the "L" of LAB, are pretty much identical.

So I just stick with the "L" of LAB since it's far easier to get to.

But the "H" and the "S" sure come in handy at times!

Regards,

Michael

[ratherbsouth]

Many Thanks Michael,

I will pick up a copy of the book that you mentioned. Looking forward to learning more about the technique.

Andy