Blinky2004

First off...
I see nothing wrong with a nice "friendly" debate between "friends" over a topic such as this. It help gives those not in the know more information to draw from. Just remember that's it's a friendly discussion, not a heated one. So bone-up on your facts, and come out shootin'. Just make sure your gun has blanks, not live ammo.

And second... those saying that RGB was created for graphics displayed on a monitor, are correct. The point about the Web is mute, since it too is "displayed on a monitor". The more specific way to explain this would be to say that RGB is better suited for the Web; not created for it. That's too finite a statement for this topic.
As for my own input on this... i don't really have one, since my print experience is quite limited. But trust me... i've seen this subject explained every which way it can be by competent professionals... and it always comes out the same... research it and decide which method is best suited for you and your own specific purposes.

And third... Doug, just because Erik is a MOD doesn't mean he knows it all... and he would never imply that. He's a very educated and experienced Photoshop user and artist. And his MOD status has absolutely nothing to do with his input on any topics discussed (and this goes for every MOD on this Forum, including me). So to say "(Mod or not)" sounds like a personal stab at Erik. Please refrain from that mode of deliberation, debate, whatever it is. It's unnecessary.

Ok so... load em up! [righton]

Rick

Good link there C9 [righton] Some good info there - thanks

Bacardi

Me too, I work in LAB, but that needs some power-training.

OK then, a real discussion. I'm ready for it.

So, my arguments why to convert to CMYK at the very end are as follows:

1/ A monitor can only display RGB. Not the complete set, but only a small part of it. Some of the newest monitors can display sRGB, a very small color space that cannot even cover CMYK. Which is why Adobe RGB is better as colr space when working for print. Which includes home/deskjet printers. You cannot see CMYK on your monitor. Never.
2/ Photoshop does not have to convert colors all the time, and its algorythms are not forced. You can verify this easily in the following sub-points of my argument:
a/ image blending is far superior in RGB mode
b/ blending modes are a nuisance in CMYK as they give even more unpredictable results. The why is easy to see: Photoshop has to convert CMYK to LAB, do its internal calculation and then, finally, has to convert back to CMYK.
3/ smaller filesize, but that is of less importance on nowadays
puters
4/ Which CMYK are you talking about? As a pro, which you claim to be, you know that there is a dot-gain, a black, and a white point. You also know that it makes a lot of difference to work for a high-class glossy magazine, and a newspaper, a cheap postcard and an art poster that has to be IRIS printed.
5/ Our eyes also use RGB. CMY are IDEALLY the opposites of R, G and B. But anyone with a minuimal knowledge of printing knows, and this can also be verified in Photoshop by comparing 0,0,255 in RGB with 0, 0, 100%, 0 in CMYK, that inks are far from ideal. Which is, amongst other reasons, the reason black ink has to be added to get anything darker than a muddy brown, and why better printers, offset and deskjet, use more than four inks.
How are you going to work with those in CMYK? RGB offers the advantage of being press/quailty-independant.
6/ Colour corrections are far more easy to perform in RGB
7/ All adjustments are better in RGB mode. Try to desaturate in CMYK if you want to see what I mean.
8/ You have more filters at your disposal and they all work better.
9/ Alistair most probably wants to print on his home printer. Most home printers prefer RGB files as their software is made to convert from RGB (often sRGB) to CMYK internally.

The method to follow, as I already mentioned earlier, is called proofing. Bst way to do this is to open the document in a new window. This makes that every change is applied to both versions, except for the option to change the color mode. Set the copy to CMYK. Now when you do your last corrections on the CMYK, both are changed. This way, your AdobeRGB file is perfectly tweaked for printing.

The only advantage of working in CMYK is when colouring line drawings like for comics when you know they will be printed on a four-colour offset press because then you literally paint with inks.
Best way to do this is to duplicate the black channel and load it as a selection on a new layer. Fill this selection with black, and work on layers below it.

I posted all my arguments here, so you can study them and shoot them off, replacing them with you arguments why one has to use CMYK from the start when working for print. And please use arguments from your own experience, not some web-adress with someone else's knowledge.


This said: I also prefer LAB. I scan 48 bit, and LAB. THis gives the best master file possible. 48 bit offers the necessary tools (even in PS7) to make the last adjustments on the histogram that are necessary.

retired_paddza

Erik - I'd agree with most of what you said with the minor exception of point 5. We see in a relatively additive nature, but not specifically RGB. It could be argued that we preceive in the RYB or HSB or HSV spaces. Even, to a degree, in CMY (the actual color compliments to RGB, K is just because we have poor technology for ink).In fact the CIE L*a*b color model was developed to more accurately describe color as a human would perceive it... and more importantly....

Point 2: Lab is profile independant. Lab color is the basis for any work that you do in graphics. The engine for photoshop is built around the Lab model and either of the other models have to refer to that model to make anything happen (hence the conversion loop the loops that you described when moving in and out of CMYK).

The major disadvantage, as you pointed out, is that L*a*b... while more accurate, is horribly hard to deal with conceptually. It's much easier (since we're taught this from preschool on up) to deal with mixing colors together from separate pots rather than degrees of color. This is why a lot of print people tend to work in CMYK all the time even when it's actually not the best space to be in. CMKY is literally dealing with mixing different amounts of ink... this makes conceptual sense when you think about it in those terms.

Regardless of the method you use, it's always best to try to not convert your document unless necessary. Since photoshop is already thinking in Lab for the most part, going from RGB to Lab isn't a major problem (ever notice how quickly it does the state change compared to other color spaces ). When you step into another color model though, you're asking Photoshop to make changes to the core data in the document. So, since all photographic data starts out in RGB when it gets into the computer, you're better off leaving it that way until you need to make the change. Since most home printers do their own color conversions and you'll break things by second guessing them, it's best not to make the conversion with your software, but instead let the printer use the profiles that are built into them for that specific reason. The only time I really work in CMYK is when I'm in Illustrator and I'm building something that is going to go out for offset printing, and usually it's has to have some kind of spot color in it. Regardless of my workflow, I always make duplicates of things that I'm working on to combat that loss of data. If I am forced to convert a document's color space, I always save a second copy to work on, because you lose data when you make the conversion.

While I prefer the control over luminocity that Lab gives me, even then sometimes I find it hard to deal with some operations solely in Lab (back to that preschool thinking we've been drummed with ) so I'll make a live duplicate of the document that is in RGB into Lab and move pieces back and forth between them. When Working with something that requires the luminocity data, I'll most likely move the L channel from a Lab document into either the channels or layers (depending on what I'm doing) of the RGB document. This gives you the simplicity of working in RGB, but the power of working in Lab. Just a personal preference though, I don't know that someone who was comfortable working in Lab would really need this, as I think you can pretty much do anything in Lab that you can do in RGB, featurewise.

One last tidbit on the magical world of Lab color and then I'll stop rambling. One of the best techniques I learned over the years was to stop using the "greyscale" conversions done by Photoshop automatically. When you want to go from color to monotone, switch to Lab, go to channels, click on the L channel and switch to greyscale. It will then give you a window prompting you if you want to delete all other channels and use the current channel. Click yes. This creates a greyscale image based on the luminocity of the photo rather than on the averaged luminocity derived from the component RGB channels. This is closer to what actual black and white film would do (not as robust, but closer) and you will get a much more dynamic photograph as the result.

Well, that's more than a mouthful, I'll stop now $0.02

Bacardi

I fully agree with you.

What I intended to say is that our eyes have little "cells" in them that are sensitive to specific frequencies. And these frequencies correspond with what we call red, green and blue. We always see light of a certain frequencies pattern that activates thjose cells. Coming from a light-emitting object, the come so as to say in a straight line. Coming from reflection, thin,gs are different. For example: cyan absorbs red, so our eyes get more green and blue, resulting in a cyan-like colour. We use this in colour-correction in Photoshop.

The big advantage of LAB, apart from the fact that it offers that underappreciated gem called the lightness channel, is that it is so wide...I once read that a slide can render 75% of what a human eye can see, a monitor only fifty, and a print has to do it with merely 25%. The big advantage of LAB is that all the info is there, even if we can never see it on the monitor or the printer. As yo?u say: no problems between mac and pc, etc etc...
Another advantage is that, because LAB encompasses all colours, colours will not be clipped.

Your method for making greyscale is great. It is the most accurate one. Yet sometimes I miss the channel mixer. I sometimes use this tool to set to monochrome when I want to tweak something.

What I also love is Ctrl/Cmd clicking the lightness channel to use it as an alpha, then press D and then X to set inverse default, and fill the selection on a layer mask on a copy of the layer. This influences the blending modes tweaked by the brightness.


As for my arguments above: I will play the devil's advocate, and defend Doug against myself:

I agree that it is not necessary to use it, but there is one good reason to use CMYK: namely when you feel inclined to do so. Many people from the 'old' school (no sneering intended) have worked their whole lives with CMYK, glueing films etc. They feel home in it. Agreed that RGB has many advantages, but they have their experience to share, and everyone can learn from that. Isn't it beautiful to see how different methods can yield similar results? There is no obligation to use either CMYK, or RGB. Do as you feel comfortable. Mant painters have problems with RGB because they have been taught at school that the primaries are red, yellow and blue. They often prefer Hue, Saturation and Lightness to RGB. Nothing is wrong with that. Technique is only the background, the car you drive in, not the goal. Then why, if I may ask, did you react?

Mainly because we have a reputation of a friendly and helpful board. Unfortunately, as of lately, that reputation of friendliness has been under fire, and is severely wounded. We need time to recover. Helping people does not mean play mr. Knowall. It means listening to their question, and trying to answer that. He who wants to show what he knows/can, most often shows what he doesn't know/ cannot.
I appreciate a lot the enthusiasm, but saying (this is *not* meant personally, but in general) "this is THE way to do it", is unfriendly. Better is to say "you could try this", or "you may want to".

Quality has to be everywhere, even in what can argueably be called "mannerisms". Being courteous.

Enough preaching. Let's have some fun...

Say, I've been told that in earlier days PS had a HSB mode. Does anybody know where it hs been hidden?

retired_paddza

Ah, okay, then take it as further information, which really it was intended as. I think I was more adding than arguing anyway.

Well... If you dig around (and around and around) on your Photoshop install cd you will run across a little folder with a little plug in which works as a filter to convert RGB to HSB or HSV. It's off somewhere in those goodies folders I believe (Don't have my cd handy a.t.m.). It will change the channel data to work in those modes. I was excited to play with it when I first found it, but it seems a little bit kludgey to me. Find it and play with it. I'd be interested to hear other experience on this matter.

MisterMister

Thanks, Mark.


Well, in all honesty, it came across that way to to me (as a "know-it-all" attitude). That's my feeling about it anyway.

No one person knows everything, and obviously I was right to begin with (the RGB comment) so there was no need to carry it further.

Anyway, moving on now .........

retired_paddza

Well, in all honesty, it came across that way to to me (as a "know-it-all" attitude). That's my feeling about it anyway.[/quote]

Yeah, it does, but not who you're thinking of I'm sure.

That's very true.

That's very not true.

That would be nice. Why not join in the conversation as it stands, since there is a ton of useful information being put forth here from lots of knowledgable people, rather than popping in only to try to get a last jab. There's nothing wrong with discussing issues, that's kind of what the forums are for, as Mark pointed out. But posting just to bait an argument is a waste of everyone's time. }P

MisterMister

This was not "a last jab". I have a right to express my feelings (I would hope so anyway), so to explain it better I want to say one last thing ....

It doesn't take much to admit when you're wrong. Heck, even as grumpy as I am I still admit when I'm wrong.

And also if I insult someone or say something that insults someone, even if another finds it insulting or marginally annoying, whether that was my intention or not, at least take responsibility and apologize for it - even a fake apology is better than none at all.

In the end, it's not a matter of who's right or who's wrong, it's a matter of etiquette. I can spend all my life working with Photoshop and still have some new kid come along and tell me something about the program I never knew before.

MisterMister

You're welcome, Rick

Additive color, or RGB mode, is optimized for display on computer monitors and peripherals, most notably scanning devices. The printing world operates in subtractive color, or CMYK mode.

For more info on this subject I found this page:

http://www.cdman.com/graphics/color/rgb_cmyk.html

Also, for Alistair, I found this Illustrator CD template, which can be downloaded here.