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TIPS, converting RGB to CMYK.

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  #21  
Old 09-26-2011, 03:44 AM
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Re: TIPS, converting RGB to CMYK.

I'd do the adjustments on the RGB file to keep it fairly inside the gamut (using a best-guess CMYK-profile for soft-proof/gamut warning), and not converting to this "random" CMYK-profile and back.

I don't like needless colour space conversions, it might add unwanted dithering/banding.
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  #22  
Old 09-26-2011, 05:00 AM
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Re: TIPS, converting RGB to CMYK.

Unless you're sending film seps to the mag with the appropriate attributes (ie UCR, GCR max ink density etc) I wouldn't sweat it on the colour conversion. Just check there are no illegal cols, of which you should be intuitively aware anyway, phone their prepress dept to cover your ass, send it and bill it. Unless your client is a big player the mags won't tweak their set up to suit a few ads. Marlboro used to be able to get their corporate red special attention but they were spending millions.
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  #23  
Old 09-26-2011, 09:52 AM
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Re: TIPS, converting RGB to CMYK.

Quote:
Originally Posted by kav View Post
If you make that first conversion with default settings and no regard for what colors are present in the data, it can screw it up.
Screw up the data how? Do you have RGB images that one can test to see and better define what Ďscrewed upí and Ďbutcheredí means?

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Either perceptual or relative colorimetric conversions can produce clipping and weird effects.
Examples please. What rendering intent would you suggest otherwise?

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If you just did a straight conversion without regard for saturated colors, it will find a way to get them into a reproducible range for the profile.
What is a Ďstraight conversioní? How does one convert without regard or with regard to saturated colors with or without a profile (your methodology is as yet unclear and undefined).

Quote:
Say it's a red object.
Red is an English word we use to define a sensation in our brains. Computers donít understand what red is, but they do understand numbers. Can you provide numbers, in a color space to continue with the analogy and testing?

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Had you adjusted to get them in range, your image would not take the same detail loss. Anyway yeah you could do the round trip to cmyk back to colormatch if you want, but without making adjustments before the first conversion, the problem remains.
If the original data is in a working space that is larger than the destination color space (in this example some CMYK, lets say SWOP V2), the its out of gamut. By converting to this space and back to RGB, you provide an RGB document for the other guy to convert and they have no out of gamut colors or a wide gamut space they may not understand how to properly deal with. Thatís all the trick provides. Its a dumbed down RGB doc for dumb people who donít understand color management and you suspect would totally hose the conversion if you gave them something like Adobe RGB (1998) or ProPhoto and they had no clue it was Adobe RGB (1998) or ProPhoto because again, they have no idea how to deal with color managed data.
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  #24  
Old 09-26-2011, 12:54 PM
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Re: TIPS, converting RGB to CMYK.

Here’s the bottom line: If you hand off separated data and there are any issues with the output, you get the blame. And this can be very expensive! You have a few options:

1. Target the conversions and do a really good job, charge for that service big time.
2. Client demands CMYK and has no real target for conversion or gives you the impression they do not (they tell you to use the ‘generic conversion’ or SWOP V2 and you find out this is a sheetfed press etc). Get a delivery notice in order that is signed and specifies that you converted the data, you have no responsibility for what comes off the press.
3. Send client RGB, you’re done.
4. Send clueless client RGB such that they can’t hurt themselves (Jeff’s trick).

You either nail the conversions or you don’t and the degree in which you don’t either lets you get away with the conversion or gets you into a boat load of trouble. A $5K an hour printing process isn’t the time and place to be screwing around with color!

The problem by and large is, there is a group of clients and printers that think all CMYK is basically the same, you just ask Photoshop to convert the data from RGB to CMYK, its all done, good, ready to print. That is a dangerous and incorrect mindset.
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  #25  
Old 09-27-2011, 11:18 AM
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Re: TIPS, converting RGB to CMYK.

I typically use the Edit->Convert to Profile->(desired CMYK profile) method on a flattened copy of the file that was retouched in RGB. You'll see if any of your colors get hosed if they're now out of gamut. It's usually very saturated blues, some reds, and yellows.

When I worked primarily in automotive retouching, I handled the file entirely in CMYK from beginning to end because I was typically always working with bright, saturated colors that would instantly crap up had they been worked in RGB and converted after the fact. I can't say I've run into the same problem with fashion and beauty nearly as much, so I tend to stay in RGB.

And I have to say that nowadays, a lot of magazines, including higher end ones, aren't NEARLY as concerned with color correctness as they used to be, or at least that's my perception. Sometimes I'll flip through W or Vogue and the color is abysmal in some stories. That's probably due to a number of factors, but bottom line, to the original poster, I think you'll be fine
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  #26  
Old 09-27-2011, 11:33 AM
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Re: TIPS, converting RGB to CMYK.

Quote:
Originally Posted by eraanexact View Post
I typically use the Edit->Convert to Profile->(desired CMYK profile) method on a flattened copy of the file that was retouched in RGB. You'll see if any of your colors get hosed if they're now out of gamut. It's usually very saturated blues, some reds, and yellows.
Well hosed is one way of describing it. The facts are, the CMYK gamut canít be used to reproduce those colors. Reality sucks <g>. Thatís what should come off the press. Yes its different. But its the reality of the output.

Quote:
When I worked primarily in automotive retouching, I handled the file entirely in CMYK from beginning to end because I was typically always working with bright, saturated colors that would instantly crap up had they been worked in RGB and converted after the fact.
Nothing here has changed other than you didnít get to witness the wider gamut RGB prior to the conversion. The data is hosed as you call it (I prefer to say the color matches what youíll probably get). Reality still sucks but ignorance is bliss (you never saw the extended gamut version). There is no such thing as a CMYK capture device (even the old school drum scanners, were RGB devices).

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Sometimes I'll flip through W or Vogue and the color is abysmal in some stories. That's probably due to a number of factors, but bottom line, to the original poster, I think you'll be fine
Fine in terms of maybe the color will be good or abysmal. As Iíve tried to point out, maybe you care, maybe you donít but IF its abysmal, just donít get blamed for this. Either have a contractual out or let someone else make the abysmal color. Its not difficult to produce an abysmal CMYK conversion. Making a really good conversion is not so easy.
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  #27  
Old 09-27-2011, 12:23 PM
eraanexact eraanexact is offline
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Re: TIPS, converting RGB to CMYK.

Quote:
Originally Posted by andrewrodney View Post
Nothing here has changed other than you didnít get to witness the wider gamut RGB prior to the conversion. The data is hosed as you call it (I prefer to say the color matches what youíll probably get). Reality still sucks but ignorance is bliss (you never saw the extended gamut version). There is no such thing as a CMYK capture device (even the old school drum scanners, were RGB devices).
Yes, that's what I meant by working the file in CMYK, that what I'm seeing is what will likely print in the end. I did actually witness it in a wider RGB gamut before converting to CMYK, that's the whole point of working it in CMYK so that I wouldn't be surprised in the end with the higher saturated colors. You don't have to yell at me man, I'm on your side.
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  #28  
Old 09-27-2011, 02:27 PM
mushmush mushmush is offline
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Thumbs down Re: TIPS, converting RGB to CMYK.

I would prefer to send em' a SWOP V2 file- - IF they get RGB, who knows what conversion their using for it- or if they just let the prepress rip handle it

......It would be my take after working with a printer who insisted on RGB submissions and then used perceptual intent to convert, killing my 3/4 tones; so I'm a little gun-shy

oops!i meant to add the thumbs down at the end

Last edited by mushmush; 09-27-2011 at 02:28 PM. Reason: change in text
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  #29  
Old 09-27-2011, 06:56 PM
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Re: TIPS, converting RGB to CMYK.

Quote:
Originally Posted by mushmush View Post
I would prefer to send em' a SWOP V2 file-
Even if the press isnít a web press, or conforms to SWOP V2?
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  #30  
Old 09-28-2011, 04:00 PM
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Re: TIPS, converting RGB to CMYK.

Quote:
Originally Posted by andrewrodney View Post
Even if the press isnít a web press, or conforms to SWOP V2?
Ah! Yes, I should have added the caveat- if I could not get a profile from printer . I would have use my best guess as SWOP V2.

Now in the op's post, this was to be a very large run- so I can't begin to explain why there isn't that level (profiled press) of color management.
That expense is mostly on the printer side: materials, man hours, utilities..etc
But OP must remember:: This is a large run and if I want more work from this person I should make sure they're happy. The relationship between that Publishing company and that Printer is unknown to me.

You could try calling someone in the Graphics department for the Magazine and ask what their color settings are for InDesign or Acrobat.
If they don't know what you're talking about, it's 99/100 gonna be default SWOP for the CMYK setting.
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