RBG vs CMYK printing - leave on RBG?

[Sam889]

Hi all

I am creating a big poster and wanted to query the use of RBG vs CMYK. So i understand that one should use RBG for display on a monitor and for web products etc. and CMYK for print products (such as a poster) however, if I import a nice colour image into a document set to RBG, it prints very nice, colours vibrant.  If I then set that same document to CMYK and print that same image, it appears washout out and dull.

So my question is, why not leave my document set to RBG? it may not reproduce exactly whats displayed on my monitor, but its much closer than using the CMYK?

Thanks for your assistance.

[Silkrooster]

When sending an image to a printing service, ask first as some require the image be rgb.

If you don't mind the slight color shift, then don't worry about it. The exception is a printing service that requires cmyk.

[Phoenix15]

you should correct the washed out cmyk version in photoshop, then bring back into illustrator. it's good practice to never print in rbg mode.

[Monika Gause]

Phoenix15 schrieb:

you should correct the washed out cmyk version in photoshop, then bring back into illustrator. it's good practice to never print in rbg mode.

That depends on the printing process. Large format printing might actually be completely different.

[Test Screen Name]

If you are using a CMYK printer, with a CMYK driver, and you convert a file to CMYK using the correct profile for the printer, the results should be the same as printing RGB (though drivers may do certain improvements).  I suspect you are converting to CMYK without selecting exactly the right profile, which is damaging.

Also, non-PostScript printers, at least on Windows, only accept RGB data for printing, and convert to CMYK themselves. If you convert to CMYK, then to print it must go back to RGB again and again to CMYK - very poor.

[Andrea Spinazzola]

First of all we have to distinguish the input process from the output process.

Second, RGB color mode is no more related exclusively to video or web environment as someone said. This is only an ancient convention that has no sense today.

Third, It depend on nature of the image that you have to print.

With these three statement in mind, I can explain how to precede.

Related to first point, you can import in your document both RGB and CMYK.

If your output device work exclusively in CMYK colo space you have three choice:

1. Convert your images before importing them in AI (in this case I suggest you to ask to the service the color profile used by the printer so you can match the input values to the output values)
2. Leave the the images in RGB when you import them in AI and export the document as PDF using the PDF settings for color conversion. In this case, if you don't know wich printer color profile to use, and if you know that the printer can print CMYK only, so the best way is to use the PDF/X-1a:2001 setting, that automatically convert the images to CMYK.
3. Leave the the images in RGB when you import them in AI and export the document as PDF or leave in AI. Usually the modern RIP (Raster Image Processor) software can automatically convert the images as needed by the printer with the correct color conversion.

If your output device work exclusively in RGB, leave the images in RGB and don’t convert the images in any way.

You can print directly from the AI file or save as PDF, if you prefer you can use the PDF/X-3 but be sure that the PDF color settings maintain the RGB color mode.

In conclusion, in 90% cases, you will prefer to maintain the RGB color mode for your images.

Is the right choice for many reason:

- The gamut is more extended than CMYK so you can print all (almost all) the colors contained in your images (on RGB printers).

- The images can easily shared on other project for web, mobile, screen without losing any colors.

- The images are lighter than CMYK

- Color correction is more easy (it depend case by case) due to the fact that your gamut is more extended and the blacks (k) are not "cutted" by the CMYK conversion.

There are a 10% cases where you should convert your images in CMYK before the output. This is related to the third statement, it depend on the nature of the images.

In some cases, with darker images o lighter images it could be more convenient manage the blacks so you need to convert in CMYK.

In few words, leave the images in RGB and try to go deeply in knowledge of color management, print and PDF.

Hope this would help you.

Ciao,

Andrea  Spinazzola

[Mike_Gondek]

Depends on your output device and color management settings

If printing to

==========

Lithography - CMYK

Large Format inkjet printer/Giclée with more than 4 inks - RGB

Lambda/Lightjet/Chromira - RGB

In most cases for posters you are printing a large quantity and you will go to lithography so unfortunately your colors will dull a little going to a destination colorspace of CMYK that has less vibrant colors. The good thing about you switching to CMYK before you print, is that you can improve the color, and not get a surprise when you print, if you are using a hardware color calibrated monitor.

If you are printing a few posters for personal use (inkjet/Giclée), or a museum quality chromogenic print (lambda | Océ LightJet | ZBE Chromira) stay in RGB. The chromogenic printers are actually RGB exposing to silver Halide, where the inkjets have more than 4 inks so they can simulate the RGB gamut well especially if you have good software for the conversion such as GMG.

[Jacob Bugge]

Sam,

In addition to what has been said already, it may be noted that if you need CMYK for printing, for greatest possible consistency (CMYK and RGB versions as close as possible), you should consider starting in CMYK and then convert to RGB in special files for RGB use. That will give you duller colours on screen but prevent disappointment (and others wondering) when things are seen in print.

In some cases, everything actually starts with Pantone inks/colours (such as corporate/official colours) which are used for primary print, and which may be converted to CMYK for secondary (less critical) print and/or to RGB for screen use/secondary print, and there may also be a choice whether to make the CMYK and RGB versions as close as possible.

[Andrea Spinazzola]

Sorry Jacob,

but I totally disagree with your statement.

A CMYK image converted in RGB produce the same colors of a CMYK image (not converted), either on RGB or CMYK printers.

An RGB image printed on RGB printer, can access to all the RGB gamut and that's why is not the same thing.

The CMYK gamut is contained in the RGB gamut but not the opposite, especially if you print on plotter or printer with extended gamut.

In other words, if you start with a CMYK file you automatically cut the extra gamut provided by the RGB color space and that's the reason why you have color consistency.

This is not the right workflow because once you convert from RGB to CMYK (or start in CMYK) you loose the gamut, so your images probably will look well on CMYK devices but not on RGB (digital prints, fine arts, web, plotter, ecc.).

If you need to manage the color consistency you have to use the "soft proof" using the color proof option in PS, AI or ID.

The color proof allow you to add the same printer profile that will simulate on screen the appereance of the RGB colors when they will be reproduced on CMYK printers.

This is the color management introduced by Adobe and of course is the correct way to manage color variation from screen to print.

The color proof can also simulate the paper and the black ink.

Nothing personal but this is what I've learned from Adobe and this is what I teach to my studensts every day.

Ciao,
Andrea

[jdanek]

Try to refer to RGB as RGB.  How big a poster are you talking about?  What profile are you using for your RGB image files?  Always follow the parameters set by your print vendor.  As part of that communication, always discuss the project with your print vendor first, then proceed onto file preparation.