RGB CMYK LAB and Dan Margulis !

[Hello_taipan]

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.

[edgework]

Originally Posted by Hello_taipan

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.

[lurch]

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

<C>

[Markzebra]

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

[Hello_taipan]

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!

[jenniferfrances]

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?

[Michel B]

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

[edgework]

Originally Posted by jenniferfrances

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.

[Markzebra]

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.

[Tom K]

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

[KR1156]

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

[MatthewMarshall]

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.

[mayday]

Originally Posted by Markzebra

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!

[cricket1961]

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

[Markzebra]

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.

[cricket1961]

Originally Posted by Markzebra

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

[Sistere]

Originally Posted by edgework

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.

Damien

[Kevin Connery]

Originally Posted by mayday

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.

[mayday]

Originally Posted by Kevin Connery

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.

[Markzebra]

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

[mayday]

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

[cricket1961]

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

[Markzebra]

"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.

[cricket1961]

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

[JMB]

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

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

[pixel_monkey]

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.

[KR1156]

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

[Sistere]

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

[Markzebra]

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.

[KR1156]

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.