Been reading Dan Margulis these days (thnx adamz!) and a whole new world opened to me: (2 actually) CMYK and LAB.

what brings me to wonder about the importance and avantages of each mode.

Why, when, n how do you guys choose to work in which mode ?
i guess it's not about one being used to work in rgb or cmyk or lab, but rather exploiting the properties of each one.

Been reading Dan Margulis these days (thnx adamz!) and a whole new world opened to me: (2 actually) CMYK and LAB.

what brings me to wonder about the importance and avantages of each mode.

Why, when, n how do you guys choose to work in which mode ?
i guess it's not about one being used to work in rgb or cmyk or lab, but rather exploiting the properties of each one.
As Dan likes to say, every file has 10 channels. Even if you don't need CMYK for output purposes its four channels are a great source of targeted masks. Borrowing a black plate for use as a layer mask in RGB and LAB gives you a shot at much more refined shadow work than either space is capable of simply using master RGB curves in luminosity mode (like taking a sledge hammer to open a jewelry box) or the lightness channel in LAB (still too much punch and no subtlety).

The C, M, and Y channels tend to contain more pure color information than corresponding RGB channels simply because the shadow detail has been removed and sent to the black plate. Subtraction operations with Calculations are a good way to isolate specific colors for masking purposes (for example subtracting magenta from Cyan leaves you with a fairly decent green selection).

In LAB, you can achieve similar results using the Blend-if sliders, much more effectively than RGB or CMYK. Each color channel in those spaces affects two different colors at once (Magenta will cover everything from orange to purple, Yellow everything from Green to Orange and cyan shows up in green through purple), whereas in lab, you can focus on red, blue, green or yellow separately, to much better effect.

If your colors are looking dull, nothing brightens them up like LAB. Increasing saturation in RGB is not the same, since by definition, increasing saturation in a color removes what Margulis calls the contaminating hues, which are what provides detail (pull all the magenta out of green leaves and you're left with a bunch of bright green blobs). And there is nothing to compare with his Man-From-Mars technique in LAB for bringing out colors that you think aren't there. A great move (in moderation).

Even if I'm not outputting in CMYK, a move into that space for skin tweaking is always called for. RGB can be a bit of a bludgeon with skin. CMYK curves are far more subtle. And a contrast curve in the magenta channel with the adjustment layer in Luminosity mode works wonders on a face that has more or less correct numbers but looks flat and dead.

And LAB is the space of choice for killing color casts, as far as I'm concerned; one, because you can easily attack color and not mess up the detail, and two, it's easy, with Blend-If sliders, to deal with multiple casts (highlights too red, shadows too green, for example) in a way that RGB and CMYK can have a real problem with.

The a and b channels have some really bizzare applications as well, again because they are targeting discrete colors rather than each channel being a component of an additive or subtractive result. It's possible to use them for color masks that are fairly precise. Dan shows some nifty used by blending them into themselves in overlay mode to enhance tone.

If you don't need CMYK output, it's sometimes a risk to actually convert the file into CMYK, but if you can get away with it, you can bring out much better shadow detail. And sometimes you can copy the file back into your RGB master and just use the enhanced shadow areas, leaving the.

Lots of stuff you can do.

Great exposition, edgework. You've given us a good, comprehensive, color space tutorial.

<C>

Yeah you have to be very careful with LAB, its very destructive if you use it on 8 bit images and convert those straight back and forth. This process compresses the color information into a very small area of the A and B channels. One way to minimise this damage is to convert your image to 16 bit then convert to LAB, do your edits and convert back. Another point that Margulis for some reason took many years acknowledge, is that a lot of the edits achievable in LAB can be done on the original RGB or CMYK document using Blend modes and luminosity/colour calculations. Its not always necessary to damage your file by converting to a different mode.

Margulis is a great teacher, but he has never been great a technician and the folks at Abode have had a few problems over the years with this

Edgework: u're awsome. i now have folders in my head where i can put ideas in order . thanks so much.

Markzebra: thx for the precisions. i had a feeling about these damages when playing around in LAB. now u mention that ill be more careful. i'll investigate the can & cannot do under each mode.

cheers!

Being an owner of about 20 photoshop books, I am fearful of buying 20 more!
Are Dan's books the most comprehensive?
Should I go for "The Classic Guide to Color Correction" or "Photoshop Lab color.."

I am interested in learning more about working with channels & color modes (in hopes that all the material doesn't fly completely over my head)

Which is my best bet?
or does anyone prefer a different author?

Excellent explanation! I'll keep it with this other great thread:
http://www.retouchpro.com/forums/rp-tutorials/17664-photoshop-channel-concepts-power-ten.html

Being an owner of about 20 photoshop books, I am fearful of buying 20 more!
Are Dan's books the most comprehensive?
Should I go for "The Classic Guide to Color Correction" or "Photoshop Lab color.."

I am interested in learning more about working with channels & color modes (in hopes that all the material doesn't fly completely over my head)

Which is my best bet?
or does anyone prefer a different author?If you haven't read Dan's book on Lab, you should, regardless of whatever other sources you might consult. Understanding the inner workings of that space has altered my own workflow considerably. There are moves in Lab that cannot be replicated elsewhere.

His "Professional Photoshop" (latest edition) is also a fundamental source, and repeats virtually nothing from his Lab book. I'm not a disciple, I don't slavishly follow all his advice, and there are many who absolutely disagree with his approaches, particularly if they spend a lot of their time in color labs working with calibration and profiles. Dan's just not "scientific" enough for them, and they're probably right. Thing is, in the real world, where you need to get real results and satisfy pain-in-the-ass clients, Dan's techniques just work; they enable you to immediately improve your thinking about color and to produce results. So for the working stiff, it's hard to find things to complain about.

Yes - if your a beginner you may find the LAB book quite frightening. Being comfortable in a color space means taking the time to work in there. If you are used to RGB color correction there is nothing wrong with it, there are powerful Saturation moves and many of the things achievable in LAB are actually achievable within the confines of RGB. Photoshop uses LAB anyway behind the scenes to calculate things like Color range and blending. CMYK also has its uses, as an abstract space. Margulis argued for years that Professionals should always color correct in CMYK and his Professional Photoshop, is still a CMYK based book. Probably the best written but a little flawed. If you want to learn CMYK, and you should if you want a full grasp of the subject, its great

One new way to work with other modes Ive never heard mentioned yet by Margulis or anyone else - is the fact that you can use Smart Objects to do a lot less damage. Ill try and give you an example - duplicate your Background layer, convert the duplicate to a smart object. Open the duplicate and then convert the Smart Object LAB. Attach a LAB curve or any other adjustment to the Smart object and save it. Now use blend modes, blend if, to make the converted LAB version of your file interact with RGB base pixels. Now back in the master document you potentially have the full power of the 10 channels at your disposal, with no converting the base pixels back and forth. You could have both a LAB and a CMYK version of your file residing in the original, with all the power that entails - channels can be copied back and forth.

Hi JeniferFrances,

Dans book, "The Classic Guide to Color Correction" is a real head-banger.
Every time I try to read and understand more than a few pages at a time
I bang my head on the keyboard as I doze off to sleep..
The book is excellent but for me a very slow read.

I would highly recommend it...... Tom

great tip from mark. another step to a smart workflow.

RBG = rich color for web and digital use. CMKY= a better idea of what your image will look like printed. Thats the most simplest way to look at it. lol. But talking about how to edit color and in what mode, is like talking about church and religion. It can go on for days. My friends and i have a joke we call it the holy color war. because so many people have so many views about whats the best mode to edit in. I edit in both. :)

One new way to work with other modes Ive never heard mentioned yet by Margulis or anyone else - is the fact that you can use Smart Objects to do a lot less damage. Ill try and give you an example - duplicate your Background layer, convert the duplicate to a smart object. Open the duplicate and then convert the Smart Object LAB. Attach a LAB curve or any other adjustment to the Smart object and save it. Now use blend modes, blend if, to make the converted LAB version of your file interact with RGB base pixels. Now back in the master document you potentially have the full power of the 10 channels at your disposal, with no converting the base pixels back and forth. You could have both a LAB and a CMYK version of your file residing in the original, with all the power that entails - channels can be copied back and forth.

Really great tip Mark, never thought of that before Cheers!

The Dan Margulis book Professional Photoshop is great but I think he makes it a harder read than it needs to be!

Mark

Thanks for a fantastic tip! I didn't realize this and it just made my day!!
There was an application years ago that enabled multi-color space layers within a single
image. xRes. Bought out by Macromedia and then killed. Or more accurately, crunched down into a program called Fireworks.

And to think that this existed in CS2 also and I never noticed!

This is huge.... really really really huge. And I hope you don't mind if I bring it up at my class in Vegas.

Chris

Thanks for the compliment Chris. Much appreciated.. it does have its limitations and can look more powerful on first glance than is the case in practice unfortunately: Remember that the master document still needs to be in a single color mode. So your LAB Smart Object is converted back to RGB each time you save.

The advantage is its non destructive, and in the example I gave you can use LAB adjustments on your LAB embedded file to your hearts content without sucessively damaging the base pixels Margulis style. One further tip is that you can set up actions to take the LAB or CMYK channels and paste them into the master on the fly. would be nice if you could hide channels in your smart object leaving visible only the ones you wanted to blend, maybe thats one for the Adobe Feature Requests.

Thanks for the compliment Chris. Much appreciated.. it does have its limitations and can look more powerful on first glance than is the case in practice unfortunately: Remember that the master document still needs to be in a single color mode. So your LAB Smart Object is converted back to RGB each time you save.
.

Ah, but when I saved down a RGB master image with a cmyk smart object and closed it and reopened it, the smart object was still CMYK.
Conversely, a master CMYK was still retaining a RGB AND a L*ab smart object.

This is great, at least for my workflow.

Chris

As Dan likes to say, every file has 10 channels. Even if you don't need CMYK for output purposes its four channels are a great source of targeted masks. Borrowing a black plate for use as a layer mask in RGB and LAB gives you a shot at much more refined shadow work than either space is capable of simply using master RGB curves in luminosity mode


Well said...Edgework. Extremely useful and most importantly...pretty damn practical. In fact, I printed it out and stuck it on my wall over my monitor for reference since I am still sucking my pacifier in regards to using CMYK & LAB.

Thanks for taking the time to sit and write something meaningful and not just a criticism or opinion. :grin:

Damien

The Dan Margulis book Professional Photoshop is great but I think he makes it a harder read than it needs to be!
It IS a tough read, but the simplified versions used in 2 other authors' books took longer to cover less material and in less depth. I'd prefer a book which can be re-read to something which doesn't give as much coverage.

The LAB book is, however, much easier to follow, in my opinion.

It IS a tough read, but the simplified versions used in 2 other authors' books took longer to cover less material and in less depth. I'd prefer a book which can be re-read to something which doesn't give as much coverage.

The LAB book is, however, much easier to follow, in my opinion.

Don't get me wrong its a great book, and for its information one of the best around, just not sure I like his writing style.
I have'nt read the LAB Book yet but looked through it and it seems better and more direct.

Fiddling around today I realised that you actually CAN hide channels in the Smart object file by unchecking the channels in the Advanced blending options - For example if you wanted to blend The A channel of LAB with your RGB document, open your LAB smart Object, Option Double click the Base LAB and turn off the L and B channels. Now save the smart object- your A channel will now appear intact in your original RGB document, converted to 3 channel RGB obviously (weird) but still useable. There you go even I learned something today.

You are welcome to use this Chris. By the way, what part of your workflow uses this? For me its alpha's and Getting a K density channel into RGB

Another great finding Mark! you offer some of the best advice and techniques on this site

This will allow for the adjustment of the black channel in RGB mode. Or certain calculations that work better in CMYK than RGB.
My softlight retouching is a lot harder to do in a CMYK file (more pressure needed)but now I can have a RGB file embedded and not have to worry about converting to CMYK at the end. Filters that work on RGB files but not CMYK are useable now. The list goes on and on. Having a CMYK base with a RGB smart object to tweak or filter. And within the RGB object, a L*ab object to change color or calculation masking.

Mark, I can write a whole book about just this one technique.

Chris

"and not have to worry about converting to CMYK at the end" - here's is a technique, You can have an empty "container CMYK" file with your working file as an embedded RGB. its possible to merely change your destination profle (lets say Euroscale or GMG) simply by using Assign profile on the CMYK master. No destructive after the event CMYK to CMYK coversions necessary any more if you set your files up this way. You can set up a droplet for each CMYK destination space which simply opens the file ASSIGNS the profile and then saves a copy. Non destructive CMYK to CMYK effectively using the embedded master RGB as the source each time. Pity most studios don't bother to get their heads around this stuff.

Smart objects are still too new to be used my most I've found. "Instances" too, occurances of the same Object used multiple times in a document, is another feature with a great many uses, each instance can be a different in every respect except the base pixels. This has mind boggling potential.

Now you are seeing it Mark! Way to go! Exactly what I meant by no more conversions to cmyk.
And each smart object can have multiple smart objects within. Even illustrator objects!

Like I said. This is huge.

Chris

I can write a whole book about just this one technique.

You better start to do that and I sure will buy it! XD

This is good stuff. Thanks for this very nice tip, Mark. This is probably the greatest approach to nondestructive retouching I've ever seen. The possibility is immense if not endless.

mark, chris....can you help me understand this a little better.

having the working RGB file inside a container cmyk file, going back to your RGB embeded file, the working file everytime you want to do a direct RGB to cmyk conversion. is that the point? instead of cmyk lets say euro to cmyk us sheetfed.

i must be missing something, and sure i am. it just sounds the same as, let's say i have an RGB master file. if i need different RBG>CMYK conversions, why not just go back to the RGB file and do separate save as files each time i need a different cmyk conversion. what does the embeded RGB method do that's better than save as steps?

im just having trouble following it. i get the channels and filters and blending, just not following what is so different about the conversions.

thanks

Hey guys,

Just wanted to drop a line and say that I took some peoples advice and ordered the two main Dan Margulis books listed in this thread...had'em overnighted from Amazon.

I've spent most of today with the LAB book and must say that in the little bit I have actually gotten down...the way I retouch is forever changed! Seriously!

If anyone is contemplating buying one or both of the main Dan Margulis books...but maybe are gun shy of spending the cash...do it! There are so many things I thought I knew but now realize I didn't know as well as I thought. (What?)

Thanks for the book tips guys.

Damien

Your right KR1156 - there is nothing different about it - you are effectively converting from your RGB master using whatever profile setup you have in color preferences (another flaw I agree). What makes a big difference to me is the whole thing is embedded in a single file, this is what gets confusing working with other people, having many different versions floating around - RGB, CMYK Euro, GMG retouched CMYK - maybe some pap file someone has converted using default SWOP - and THEN repurposing these CMYK files - disaster. Thats all.

There is nothing different about the conversions, and they are also flawed in that whatever rendering intent, black point you have set up in Color Settings will always be used. BUT ... if you know what you are doing its a great way to keep things clean.

i got ya mark, thanks for the clarification....i thought i was missing something and it was bugging me!

but i do like a very clean, smart & simple workflow...so we're on the same page.

I probably wont get any sleep tonight... thanks Mark! :dizzy:

i dont know why you guys all fuse so much about color conversions, when you take it to your print shop or give it to your clients to print, they are just going to hit the print button on there hp printers and let the software do what ever it wants with the file. lol lol lol

i dont know why you guys all fuse so much about color conversions, when you take it to your print shop or give it to your clients to print, they are just going to hit the print button on there hp printers and let the software do what ever it wants with the file. lol lol lol

But, this is not just color conversions. It's also a really great approach to nondestructive retouching. You have the ability to retouch at any level within the smart object layer that's within another smart object and use whatever amount of layers you want within each level and you still end up with a single layer for your master file. It sure helps my workflow enormously. I used to have to flatten all my retouching layers to just the original and the retouched version in my files and back up the masters in my hard drive before I pass them over the quality control team...it was just such a pain. Now I don't have to do that anymore.

This is not something new, though. I just realized that Deke McCelland mentioned briefly about this approach before CS2 came out. I didn't pay much attention to it back then and never thought it can be taken to this extent.

It was new for CS2, just not talked about evidently.
Be careful with the amount of smart objects you use. I had a empty base CMYK
with a RGB smart object that contained a Lab smart object. It went from 250 mbs to
1.7 gigs. No alpha channels either.
It could eat up your hard drive space rather quickly. And although it is really great, having to save a smart object each time will add an enormous amount of time to your workflow. Of course it all depends on the resolution and file size of the image.
To me, the benefits outweigh everything but the time factor. So it just means to use it when it is most beneficial to me and not any rush jobs.

Chris

I do notice the increase in file size, but it's ok for what I do here. What I meant by that Deke mentioned it before CS2 came out was that he was showing it on the CS2 space monkey beta version before the final retail release.

Chris, you brought up a good point about the increase in file size, which led me thinking about smart object instances. I haven't used them, yet. I'm assuming they should behave similar to the instances in Flash or other 3D programs out there that let you edit the look of each instance in whichever way you want as long as you don't mess with the master object and still maintain a considerably small file size . This is going to be wild if this were true.

funny thing is i use the smart object for embeded illustrator files when i do production and mechanicals...helps when i need a clients logo or something, and need to apply Photoshop effects, if i needed to modify the illustrator file, i would quickly do it and save, instead of having to copy and paste and resize and register all over again.

but i never even knew you can turn a Photoshop layer into a smart object, i vaguely remember glancing over it somewhere, but never knew how to use it.

i'm in RGB 95% of time, and don't do the cmyk conversions, so i really love the bringing in the K plate. that's where i get most use out of it.

It's amazing how unforeseen possibilities start to surface when we look at the same thing from several different perspectives. I've been possessing my raw files into smart objects so I can reopen them in camera raw whenever I wish. They're basically tiff files with just a smart object layer inside, but it never occurred to me that it can go a lot further from there.

but i never even knew you can turn a Photoshop layer into a smart object, i vaguely remember glancing over it somewhere, but never knew how to use it.

Funny that i thought it was ONLY for Photoshop layers. :grin:

mquest - try counting sheep, its more effective at getting you to sleep

I had a empty base CMYK with a RGB smart object that contained a Lab smart object. It went from 250 mbs to 1.7 gigs. No alpha channels either. yes this is true - i think its because Photoshop has to generate a full resolution preview of the embedded object in the master document, if you have a CMYK master with an RGB Smart Object there are now three copies of the base pixels: the CMYK base pixels, the RGB smart Object itself ...AND a preview of the RGB smart object converted back to CMYK which sits in the original file. Chris in your 3 level embedded version there is alot of extra data being generated to create the previews. Its also worth mentioning that your LAB object by the time it is reflected in you CMYK master has been converted twice.

Instances - yes I suppose the equivalent in Illustrator is what they call Symbols. This idea is actually more powerful in photoshop than in other software for this reason - now with smart filtering you can apply distortion filtering as well as warp, you can group multiple adjustments/curves, apply opacity, blending - all this individual to each instance. Its capable of enormous subtlety. As an example I have used them to coat a car bodywork and recently as a pitch to do skin where a potentially variable tattoo design had to be imposed on her. In practice each instance can have different perspective and distortion blending and opacity masking. Its magic when you see your entire image change before your eyes on updating the Smart object, or replacing it completely.

Markzebra is God.
thx for the tip man !

i'm in RGB 95% of time, and don't do the cmyk conversions, so i really love the bringing in the K plate. that's where i get most use out of it.


i'm trying to figure this out but can't seem to get a handle on it, how would i use the smart object to add K only to a RGB file?

i'm trying to figure this out but can't seem to get a handle on it, how would i use the smart object to add K only to a RGB file?

You convert the smart object to CMYK and adjust with curves.

Chris

Tai,

Thanks for starting this thread...I learned a ton

You convert the smart object to CMYK and adjust with curves.

Chris

ok, i got that far but i can get a similar result by just using selective color on the RGB file itself...

i'm trying to figure this out but can't seem to get a handle on it, how would i use the smart object to add K only to a RGB file?


what i do is double click on the base layer of the CMYK smart object and turn all chanels off except the K, then save. when i get back in RGB, i do the necessary blending of that K plate.

ok, i got that far but i can get a similar result by just using selective color on the RGB file itself...

True, but you are not pushing in just black. You are pushing in an interpretation of black. At least you can dial in exactly the amount of black you want.

i'm not sure what you mean by interpretation as i'm getting the same numbers when i read the cmyk values...

i'm not sure what you mean by interpretation as i'm getting the same numbers when i read the cmyk values...Those are the numbers you'd get if you converted your RGB file to CMYK. But as long as it's an RGB file, your shadow detail is blended throughout the three color channels. The difference is that when you manipulate a K curve in CMYK you are dealing with only shadow information in a way that RGB and LAB cannot match. I've used the K plate as a layer mask to refine my shadow moves in RGB, but it's not quite the same. That's why Dan always says that CMYK is the best space to work with shadow detail. And nothing beats the effect of sharpening the K plate only, not possible in RGB.

i'm not sure what you mean by interpretation as i'm getting the same numbers when i read the cmyk values... - This is a useful technique - what Chris means by interpretation is a re-separation of the K channel back into RGB. Its the same as if you had duplicated your RGB document, converted the duplicate to CMYK, copied the K channel, and pasted this copy from the clipboard back into your original RGB document. If you now look at your three RGB channels you will see the K channel dropped into the R, G and B in equal amounts - because photoshop has made your copy into a new desaturated layer. Each of these channels is identical to the K channel in CMYK.

Glad everyone finds this stuff interesting and useful, Smart objects after the release of CS2 took me a year or so too for me to get my head around, because they were so new. But they are a pretty important usability breakthrough I think

Oops sorry edgework,I duplicated your answer there. Yes Its about shadow detail density. In CS3 You can of course use a Smart filter on your new K layer to sharpen it - you could for example apply a blend mode to the K layer, maybe multiply? sort of like the opposite of a shadow highlight, bottom end density control with a scrubby slider.

definitely something to master but i can't justify doubling a file size everytime i need to add black to an RGB image, at least not at my current gig...

I had two questions:

first, I like your tip edgework on sharpening the black plate. How would you do this? I tried to copy it on a new layer, run high pass, and change to overlay blending. It looks interesting that way. Is there a superior method you use?


Second question is, I'm fully aware of how each mode has its own seperate gamut, but I've never come across color shifts unless printing or uploading to web, etc. Except when switching modes with lots of layers and masks. So can someone give me reasons, or better yet examples where switching modes under normal circumstances are bad?

I had two questions:

first, I like your tip edgework on sharpening the black plate. How would you do this? I tried to copy it on a new layer, run high pass, and change to overlay blending. It looks interesting that way. Is there a superior method you use?You're thinking too hard. I meant sharpen the K channel. Literally. Go to your channel's palette, activate only the k channel and sharpen it. Works particularly well for faces since there is virtually none of the textural detail in the black plate to get grunged up. Eyes and hair can take a heavy hit and always look better for it. Do this on a duped layer to blend as desired.

Second question is, I'm fully aware of how each mode has its own seperate gamut, but I've never come across color shifts unless printing or uploading to web, etc. Except when switching modes with lots of layers and masks. So can someone give me reasons, or better yet examples where switching modes under normal circumstances are bad?

Not bad, necessarily, but the reality is that CMYK is incapable of producing many of the colors you take for granted in RGB. Find a picture of a vivid blue dress with lots of variations in blues and greens for detail. You'll find that with the default conversion in Photoshop, which is Relative Colormetric, all those subtle shifts in tone will pretty much turn to mud. Blues and greens suffer particularly, as well as vivid purples, turquoise and oranges and virtually all pastels; they are simply out of the normal printing gamut for CMYK. (Reds fare better and Yellow is actually purer in CMYK.) Photoshop converts colors that are in gamut precisely, and the stuff that's outside the range gets crunched at the edges. Hence the blue mud. The other useful conversion mode is Perceptual which recreates the relationship between all the colors but which will necessarily alter all of them in order to do so. It's useful when you're not going to get the original RGB color anyway and at least want to maintain detail and a reasonable facsimile of the original intent. Other options would be to pull out the lightness channel from LAB, or one of the RGB channels that captures the needed detail, copy it before converting, then layering it in on top of the image in luminosity mode. You'll need to play around with moves like this, and you'll send your colors way south, but, again, the colors weren't there to begin with. If it's a toss-up betwen bad color and bad detail, or color that's off but which has clear detail, go with the second.

Of course, not everything goes to a printing press these days, but if you need 1000 copies of something, you'll need to navigate the mysteries of conversion. (Just remember that every beautiful image you've ever seen in a book, magazine or poster has managed to get around these limits, so all is not lost.).

Yes -everything that edgework has said is 100%. Having some sort of production experience helps a lot in knowing what a good CMYK file is, and that just converting an Adobe RGB file to PhotoshopSWOP default is a no-no. The key is the black plate. Each press varies immensely in how it handles the black ink: whats the ink limit? what kind of GCR do you need? ie how HEAVY is the black plate as it stretches into the lighter tones of the image. Images vary too, more monochromatic images can benefit from a stronger K plate which helps their detail and highly saturated images a lighter K.

By the way Margulis is a good teacher in these areas because thats his background I reckon. Edgework has given some good advice there about moves on the L channel (which can now be a smart L) and a lum blend on this, thats great technique which I use. Luminosity blend uses LAB calculations fairly non destructively without any conversions actually you can just use adjustments with a Luminosity blend with tremendous power.

Hi guys and girls,
I am reading my way through the LAB book and found some difficulty following the calculation instructions....it states that in the calculation screen choose green channel and it should be applied to the whole picture (all other channels if none is selected). In CS3 I do only have the option the choose red, blue, gray etc. Would that in conclusion mean that I have to dup the layer twice and apply the green channel in the first dup to the red channel, and in the second copy to the blue channel? Wouldn't a channel mixer be more appropriate? Please let me have your thoughts, as I am lost here. Thanks