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Trouble Following CMYK Separation Procedure

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Old 06-02-2003, 11:02 PM
Jeff F Jeff F is offline
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Trouble Following CMYK Separation Procedure

On page 139 of Richard's book, while attempting to create the Luminosity Mask, I'm not getting anywhere near the result I get when choosing the "CMYK Black" tool from the Hidden Power Tools menu. When I accomplish steps 4 and 5 in the book, I get a 50% gray mess as the "Black" layer. It's impossible to tell that there's a man in the photo. However, if I move the Saturation layer above the Luminosity layer then merge these two layers down to the "Black" layer, I get a result that looks a lot more like what I get when just using the tools menu. Perhaps I'm misreading how to do this. Certainly I'm having difficulty understanding how the luminosity mask and the saturation mask work together to create the "Black" plate. Anyone who can shed light on this issue please feel free to comment.

Thanks,
Jeff
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Old 06-03-2003, 09:02 AM
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Richard_Lynch Richard_Lynch is offline
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You need the luminosity to focus on the darker part of the image, and the saturation to focus on the grays and blacks rather than colors. If you were to mix black into colors they would tend to get muddy. The Black plate is technically only supposed to affect the very darkest of colors.

Luminosity masking alone won't do it.

That help?
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Old 06-03-2003, 10:09 AM
Jeff F Jeff F is offline
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Thanks again for helping me out here, Richard. I believe that I understand now why we need the luminosity and saturation masks. However, in my original post I was more concerned about whether or not there is a mistake in the steps of the book or if I'm misreading it somehow. It says to move the saturation layer above the Black layer then merge the two. This leaves the luminosity layer out of the mix -- it's still on top of the stack but uninvolved in creating the Black layer it would seem. But if I move the saturation layer to the top of the stack and merge down to the Black layer, the luminosity layer is sandwiched in between and is part of the solution. It also looks more like what you get if you just use your tools from the CD. Is this a mistake in the book? I'm just trying to get the best understanding that I can from this very difficult subject matter.

And since you brought up the notion of muddying the colors with black added to the CMY separation, even after using the Hidden Power tools to accomplish the CMYK separation on Gorskii's photo, the result muddies the colors a little as compared to the original. Is this simply a trade-off that one has to accept for adding black ink to the mix? Is it possible to get an exact separation that looks identical to the original while using a black layer? Or is this just a problem with showing a CMYK image on an RGB device (monitor). Sorry, but I've been unable to try out the actual printing of this yet. I am looking forward to it, though. I played with it onscreen for quite a while last night to try and figure it all out, but I was unable to get colors as bright as the original without deleting the black layer altogether.

Any thoughts on these subjects would be greatly appreciated,
Jeff
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Old 06-03-2003, 11:02 AM
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Richard_Lynch Richard_Lynch is offline
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RGB is not the same as CMYK, as it says in the book. RGB and CMY will look identical on screen, but the print will notably fade. Black has to be there to emphasize the tonal dynamic you won't get from CMY inks alone.

About the steps...Step 4 does say to move the saturation layer above the black layer. This will lighten the result of the black layer -- effectively masking the saturated colors for being tainted with much black.

I'm pretty sure those steps are correct -- the tools were built to mimic them. If you have the HPA2 action player, you can slow down the playback speed and open the layers palette to watch the steps occur.

That help?
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Old 06-03-2003, 12:06 PM
Jeff F Jeff F is offline
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Ok, I think I found the problem. I slowed the action down, and it appears that the Luminosity layer it grouped to the Black layer (actually 50% gray), changed to a luminosity blend mode, then merged with the Black layer before messing with the saturation layer. I don't have the book in front of me, but I believe this step is missing from the book. If not, I apologize for wasting your time, but I read through that section a couple of times and didn't see any mention about the luminosity layer other than a levels correction. Boy, if I missed that, I'm going to have to talk the doctor into increasing my medication! But now that I've seen the action slowed down, maybe I can start to get my arms around this monster.

Thanks for your patience,
Jeff
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Old 06-03-2003, 07:13 PM
Susan S. Susan S. is offline
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I've finally bit the bullet and attempted to work through this section again, and I think Jeff's right. if I follow the instructions in the book the luminosity layer gets left sitting doing nothing - step 3 on p139 finishes the luminosity mask, but it isn't mentioned again, and isn't grouped with anything to produce a mask. The merging in step 5 only talks about the saturation and black layer being merged. (as I recall this is where I got stuck last time, and thought I must be doing something wrong as I didn't really understand what it was trying to do - I'm a little closer now!)

Actually there are surprisingly few errors in the book for so many detailed steps. And I think this is the first one that has totally stumped me. I'd hate to have to proof-read/test something like this....(my husband's law texts are bad enough!)
Susan S.

Edit: to add - I've just run the actions for the CMYK Black tool - this does appear to have other differences to the instruction in the text as a curves dialogues appears (I can't find any reference to curves in the text version...I guess I need to step by step thru' it to find out but I'm suffering a caffeine deficiency this morning! - my guuess is it is in place of one of the levels adjustment layers)

Last edited by Susan S.; 06-03-2003 at 07:36 PM.
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Old 06-03-2003, 07:50 PM
Jeff F Jeff F is offline
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Hi Susan,

I'm glad it wasn't just me getting lost at that point. I, too, noticed the addition of the curves layers after slowing the action down. I believe they are in there to make the tools more complete for those with expertise to be able to fine tune their results at each step of the separation. My guess is that Richard left them out of his manual steps so as not to add difficulty to an already complicated procedure. He does, however, mention their availability throughout the text for the separation for making precise changes to the different color layers. I must confess that I have struggled with the black layer part of this separation, and even now am only on the most rural outskirts of understanding. But that will probably have to suffice for now at my current experience level.

Good luck with those law texts,
Jeff
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Old 06-03-2003, 08:26 PM
Susan S. Susan S. is offline
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Jeff - I'm now at the stage of understanding what the CMYK separation process is doing and the role of the different masks- I think. the next step is getting on top of the steps that are used to create the masks and understand that fully.

I really ought to go back to reformatting chapters that came back from his co-author with all the italics removed and in the wrong font and with all the style sheets scrambled (why do law books need that many footnotes?!!)....but right now CMYK is more interesting!

Susan S.
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Old 06-03-2003, 09:53 PM
Jeff F Jeff F is offline
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Susan - I'm glad you're getting a handle on the CMYK process -- that's one more person who can answer my questions. As for me, I know I need to devote more of my energy toward gaining experience in more basic correction processes. But I'm just too inquisitive, and it will bother me until I have a firm grasp. As long as I keep making forward progress, I'll be alright. And thanks to Richard's book and all of the help I've received here, I'm headed in the right direction. (Note to self: Crawl first, then learn to walk).

Jeff
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Old 06-06-2003, 09:58 AM
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Richard_Lynch Richard_Lynch is offline
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Finally had a chance to check this. You should merge the Luminosity and Black channels between step 3 and 4 -- there is indeed a step missing. If you try it with the tool, you can follow along in the steps and it becomes pretty clear what is going on. The Luminosity is used to generate tone for the black -- it is then corrected so that the black only is introduced at 50% or darker tones. It is merged with the black layer to do 2 things: change the mode of the layer and change the name to Black.

I'll have to get that in the errata. Thanks!
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