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Input/Output/Workflow Scanning, printing, color management, and discussing best practices for control and repeatability

colorspace question

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  #11  
Old 03-21-2010, 08:39 AM
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julie_swiderski julie_swiderski is offline
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Re: colorspace question

does anyone know why a printer would prefer a grayscale file over desaturated rgb file for printing black and whites on 4 color press?
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  #12  
Old 03-21-2010, 02:39 PM
pixelzombie pixelzombie is offline
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Re: colorspace question

a desaturated image will look very flat in certain areas
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  #13  
Old 03-21-2010, 03:24 PM
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Re: colorspace question

im having quite the opposite effect. the grayscale image is flat and muddy with no contrast, the desaturated rgb file has much more tonal range and contast, with much richer blacks.
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  #14  
Old 03-21-2010, 05:12 PM
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Re: colorspace question

When printing a "neutral" gray image. A 1/c Black "grayscale" file will stay neutral due to the black only. When printing a neutral gray image made up of 4/c a straight conversion from rgb to cmyk will give you full cmy neutral and a skeleton black (dark shadow end only). This will be tough to produce as neutral on press because of ink balance sensitivity and other press conditions. A custom profile or action build to create a lighter perhaps shorter ranger cmy and a heavier longer range black would help on press to keep neutral but also have some extra depth and detail.
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  #15  
Old 03-21-2010, 07:59 PM
Kermy Kermy is offline
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Re: colorspace question

Use prophoto or adobe 1998. prophoto preferably as this has the widest gamut. but you need to do this from the start when you convert your raw files. theres no point assigning a profile once its converted. and once you have done your retouching you will need to convert to cmyk. what you should do is go to 'edit' then to 'convert to profile' and select a Fogra labeled cmyk profile. Fogra 39 is the best one out there at the moment. And what this does is provide the best rgb to cmyk conversion possible, as some colours don't convert to cmyk too well. you loose vibrancy, especially in reds. so you might have to slightly tweek the cmyk when its converted. But by choosing the Fogra engine for conversion you are minimising the difference that exists between rgb and cmyk...
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  #16  
Old 03-22-2010, 08:44 AM
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julie_swiderski julie_swiderski is offline
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Re: colorspace question

Imbet,
..."A custom profile or action build to create a lighter perhaps shorter ranger cmy and a heavier longer range black would help on press to keep neutral but also have some extra depth and detail."

im forgetting how, but we used to do this, ghosting back each channel and pasting into black, and they came out beautiful. im sitting here working on this now trying to remember how i did it, it's been so many years since i worked in prepress using cmyk. we're using rgb files here and our printer converts them.

Kermy,
our photographers do use prophoto and yes they come out beautiful but the files im using are adobe 1998 (our photographers didn't shoot the material we're using) I'll see if i can find that profile Fogra 39

thanks!
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  #17  
Old 03-22-2010, 12:38 PM
SilvaFox SilvaFox is offline
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Re: colorspace question

Quote:
Originally Posted by ImBET View Post
When printing a "neutral" gray image. A 1/c Black "grayscale" file will stay neutral due to the black only.
Grayscale B/W's do not print neutral. They print thin and ( depending on what paper is being used), toward green.

You would think they would print neutral, but not the case.

OK. Sorry. Back to profiling.
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  #18  
Old 03-24-2010, 10:45 AM
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Re: colorspace question

When printing on press the black (1c grayscale)will be as neutral as your black ink. When printing on an older inkjet your black (1c grayscale) will rip into a file that is made up of that ink set, and mostly looks green. We have an Epson 7900 which prints blacks much more neutral than our old 4800 and 9600
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  #19  
Old 03-24-2010, 04:15 PM
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Re: colorspace question

Quote:
Originally Posted by julie_swiderski View Post
Imbet,
..."A custom profile or action build to create a lighter perhaps shorter ranger cmy and a heavier longer range black would help on press to keep neutral but also have some extra depth and detail."

im forgetting how, but we used to do this, ghosting back each channel and pasting into black, and they came out beautiful. im sitting here working on this now trying to remember how i did it, it's been so many years since i worked in prepress using cmyk. we're using rgb files here and our printer converts them.
I came up with a similar technique because I was sick of seeing casted 4-colour black and white images.

Starting with a real nice looking monotone-RGB or Grayscale image, try this:

1. Load the luminosity as a selection (opt+cmd+2 in CS4)
2. Save selection as an alpha channel
3. Create a new CMYK document with same size/res
4. Fill a layer with a rich, neutral, black-controlled black (40/31/29/100 for example)
5. Duplicate the alpha channel into the CMYK image
6. Load a selection from the alpha channel
7. Fill the selection with white on the rich black layer
8. Create a curves adjustment layer, set blend to soft light.
9. Make an s-curve and adjust to taste


This will give you a monotone cmyk that is really neutral, because the black is so much stronger than the other colours. It will be rich because it contains all for inks. It'll also make sure there is black in all tones instead of just shadows.

Its really pretty good. Give a try. BTW I don't know how this will look on an inkjet, just good on press.

--Shift Studio.
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