i think just changing the mode of the image will be enough.

best.

On Fri, Apr 2, 2010 at 6:01 AM, TenLeftFingers wrote:

I've noticed (and since learned) that when an RGB graphic is printed on a CMYK
printer, the output can be much darker - perhaps more saturated?

Anyway, I'm wondering if anyone can recommend modification I should make to my images before sending them to the printer. I've considered simply brightening the image, but I'm thinking that there might be a smarter adjustment to make.

Thanks!
Ten

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On Fri, Apr 2, 2010 at 5:01 AM, TenLeftFingers wrote:

I've noticed (and since learned) that when an RGB graphic is printed on a CMYK printer, the output can be much darker - perhaps more saturated?

Anyway, I'm wondering if anyone can recommend modification I should make to my images before sending them to the printer. I've considered simply brightening the image, but I'm thinking that there might be a smarter adjustment to make.

Most "CMYK" printers (if you mean inkjets and lasers) are actually RGB printers. So, you can get the most accurate results using a calibrated monitor, Gimp's color management in "Color manged display" mode, and sRGB profile for your image.

You can get better results by calibrating your printer, though.

You could convert to CMYK using the separate+ plugin if that's what you want.

http://cue.yellowmagic.info/softwares/separate-plus/index.html

-- Praveen

On 1 April 2010 21:01, TenLeftFingers wrote:

I've noticed (and since learned) that when an RGB graphic is printed on a CMYK
printer, the output can be much darker - perhaps more saturated?

Anyway, I'm wondering if anyone can recommend modification I should make to my images before sending them to the printer. I've considered simply brightening the image, but I'm thinking that there might be a smarter adjustment to make.

Thanks!
Ten

--
TenLeftFingers (via www.gimpusers.com)

On Mon, Apr 5, 2010 at 5:46 PM, TenLeftFingers wrote:

Thanks folks. I didn't understand the CMYK seperator filter so I didn't use

Don't use the CMYK separation display filter, because it's inaccurate, and can lead to a lot of headache.

it. I'm pretty sure the printing company are using CMYK printers and apple computers - so I might ask them what color profile I should use.

Yeah, I thought you meant laser printers. Some people confuse 4-color laser printers with real CMYK-capable machines.

I'm designing on a cheap laptop so I guess the lack of calibration isn't helping. I looked at the color modes too but the only choice is sRGB, which I'm already using.

Calibrate your laptop display. It's nowhere near perfect, but it's better than nothng. You can get Huey at a very low price, and you can use Argyll CMS with dispcalGUI to get the maximum out of that device (software that comes with it is not very good, though).

For proper CMYK preview, you can use the Print simulation mode (Preferences > Color management). And yes, your printer's profile would help.

Get separate+ plugin (current version is 0.5.6) and use that to output CMYK file. You can use the Pseudo-Composite option in separate+ to get the separated file, and you can use the eyedropper tool on layer mask separate+ creates to see the exact output value for each channel (you'll see what I mean when you actually do all this).

You can also use Scribus to help you with creating press-ready PDFs. Scribus converts images to CMYK automatically for you. For photographic images, this is not a problem.

Regards,

On Tue, Apr 6, 2010 at 1:10 AM, TenLeftFingers wrote:

Branko, that was extremely informative. Thank you.

Yeah, I thought you meant laser printers. Some people >confuse 4-color laser

printers with real CMYK-capable >machines.

Actually, I didn't know the difference. Thanks again.

Most commercial 4-color lasers process data internally as sRGB, and everything you feed it will be converted to RGB. I've done tests on a huge 4-color laser at work, and it actually works better if you feed it an sRGB image, and set color management for the printer to proof. Of course, the sRGB file you feed it should be a digital proof of your final CMYK output, if you intend to use the printer for proofing. But the proofs produced by such printers are decidedly not reliable for any practical purpose.

In contrast, the commercial CMYK printer (real CMYK printer) and some high-grade CMYK lasers, do the separation of CMYK files into individual colors (plates), and therefore it is important that you pre-separate your files.

You can get Huey at a very low price, and you can use Argyll CMS with dispcalGUI to get the maximum out of that device (software that comes with it is not very good, though).

I've just looked those up and it sounds like these tools are almost vital.

Depending on how important color management is to your workflow, you might want to get something more serious than Huey. And a good monitor, of course. I've had decent results from my cheap monitor and Huey, but I wouldn't bet on my setup for color-critical work (like corporate identity brochures, etc).

For proper CMYK preview, you can use the Print simulation mode (Preferences > Color management). And yes, your printer's profile would help.

Get separate+ plugin (current version is 0.5.6) and use that to output CMYK file. You can use the Pseudo-Composite option in separate+ to get the separated file, and you can use the eyedropper tool on layer mask separate+ creates to see the exact output value for each channel (you'll see what I mean when you actually do all this).

I've just installed seperate+ and when I get familiar with it, I'll try this out. It seems from my first attempt, that without calibration / printer profile, the process is useless.

Yes. You should get the target printer profile, and Adobe's ICC pack. Find it on adobe.com for a free download. Most people use either sRGB or AdobeRGB as their RGB profile (not monitor profile, of course), and Gimp can extract your monitor's profile if it is installed properly, and use that as your monitor profile.

You can also use Scribus to help you with creating press-ready PDFs. Scribus converts images to CMYK automatically for you. For photographic images, this is not a problem.

I used Scribus and noticed that when exporting, there is a "For Print" option in the color dialog. The output looked too pale on screen so I didn't send this to the print company. De you think this would have solved my darkness problem?

Without properly calibrated monitor, and target profile, my guess would be just as good as anybody's.

Regards,

On Mon, Apr 12, 2010 at 1:35 AM, TenLeftFingers wrote:

Branko,

There's a wealth of information to process there - thank you so much. I really would rather do this work on Linux or not at all and you've given me everything I can imagine needing to know.

You're welcome. Party due to this topic, I did an overview of color management involving separate+. You can check it out here:

http://www.brankovukelic.com/post/513356271/gimp-color-management-for-dtp

On Mon, Apr 12, 2010 at 5:39 PM, TenLeftFingers wrote:

You're welcome. Party due to this topic, I did an overview of color management involving separate+. You can check it out here:

http://www.brankovukelic.com/post/513356271/gimp-color-management-for-dtp

I saw that and I have it bookmarked ;) The new site design is great.

Cool. Leave a comment there if there is anything that's not clear enough.

TenLeftFingers píše v Po 12. 04. 2010 v 17:39 +0200:

You're welcome. Party due to this topic, I did an overview of color management involving separate+. You can check it out here:

http://www.brankovukelic.com/post/513356271/gimp-color-management-for-dtp

I saw that and I have it bookmarked ;) The new site design is great.

You should also check with the print shop, if they have experience with colour managed work-flow and what are their expectations of colour encoding.

You would know that once you ask for the preferred profile for images in RGB space or for a particular CMYK profile of their printer. If they do not tell you much useful information, you'd better look somewhere else to have your images printed...

regards,

Milan Knizek knizek (dot) confy (at) volny (dot) cz http://www.milan-knizek.net - About linux and photography (Czech language only)