Rendering : CMYK instead of RGB


#1

I’m not too satisfied with the photoshop conversion from RVB colors to CMJN , is there a way to directly render a CMJN file in max ?

Or how do you do then for print ?


#2

photoshop conversion of RGB to CMYK is about the best you can get, the printer can either print the colour or not. The only way to make it easier is not to use vibrant colours like bright red when modelling and texturing for print.
i think max only outputs as RGB.
:beer:


#3

Ok that’s what i thought :hmm:

Thanks anyway :slight_smile:


#4

The conversion in Photoshop is probably as good as it gets. Some colors are just not there in CMYK (like bright green for example).
So rendering in CMYK wouldn’t be a solution.

Converting images to CMYK for print is a real art. There are some books about the subject, a heavy read but definitely worth it if you are going to do more print stuff.

Oi! I was slow typing this message :slight_smile:


#5

Thanks Marcel, do you know any of these books ?


#6

No 3D program can render CMYK colors. Form*Z offers a option to render in CMYK, but this means only that the rendered RGB picture is converted internally. If you are not satisfied with the color conversion, open photoshop, hit F1 and look for the conversion settings, there’s lots of interesting stuff to read.

But be careful: If you want to print your images with offset, you might want to talk to the people at the printing company about the settings they use. Otherwise it can happen that your beautiful pictures turn out really ugly. The standard for Europe is Euroscale Coated v2, btw.

You can convert your RGB image via GCR or UCR. GCR means, that the dark color are built with black, UCR means that dark colors are built with CMY, which looks a little bit different, especially in the middletones.

If you mean that all your colors are not bright anymore after the conversion: The cause for that is, that the CMYK colorspace (subtractive colors) is much smaller than the RGB colorspace (additive colors. See this ). For example: If you convert a bright RGB blue into CMYK, it looks darker and washed out.

A solution to this problem would be to print with six colors (CMYK+Green+Orange), but Photoshop doesn’t offer that module. There is software you can buy, but do that only if you are a printing professional, they’re expensive. :smiley:

So, if you want to print your images in CMYK, because you have to do that for a client, or a brochure, a magazin etc., then talk to your printing company about the best way to convert it (they will be happy that you do it yourself and answer every question).

Before you convert, add a little tiny bit noise to your rendering, because you will get moiré effects, if you don’t do it. Then convert and adjust the colors. If you have the money, let the printing company print a scitex proof or something. Take it with you, compare the colors on your screen with the print and adjust again. Do that until you’re happy.

I hope this was helpful and not confusing. It was a real fun to talk about that :beer:


#7

thanks a lot bibi5000, great informations. :slight_smile:


#8

i heard about “cinema 4D art” renders in CMYK


#9

This is the book I bought:

Professional Photoshop: The Classic Guide to Color Correction
by Dan Margulis (Author)
Publisher: John Wiley & Sons; 4th edition (August 2002)
ISBN: 0764536958

Be warned though, it is a very heavy read. Reading more then 5 pages at a time will make your brain explode :slight_smile:
Even my boss (who has been working a couple years doing print stuff in Photoshop) got some invaluable tips from that book.


#10

thanks a lot bibi5000, great informations

Thanks, being a help feels good :smiley:

Here are some links that cover the issue color conversion:

About RGB and CMYK

About color conversion. Attention: They’re talking about SWOP (American printing profile)

Color spaces

RGB vs. CMYK color space

Theoretical aspects of six-color printing


#11

I would never use photoshop to convert to CMYK, if you need output for print take it to the co. that is doing the printing and let them convert it with Professional conversion software. if the project is not that critical then by all means use photoshop.


#12

FYI:

I have used a settings file from the manufacture of the specific output device (film recorders like AGFA, Linotronic, Etc…) in photoshop to generate the CMYK data. I think this called a color settings file and includes setting for dot gain, gamma etc…

-Shea
www.Ls3D.com

:airguitar


#13

katie…ill think you’ll find 8/10 x they use photoshop to do that


#14

Yep, you can bet on that. I worked four years in printing companys.

You can use the software you want, it makes no difference if you know what you’re doing. But PS is one of the most professional tools you can get.

Anyway, if you have converted your rendered image to CMYK and you did’nt have done this before, make sure you

a) ask the printing company for settings/tips

b) if you’re getting moiré/banding in your image, especially in gradients, use the noise - filter in photoshop before you convert to get rid of it.

c) Don’t trust your monitor. If you want to calibrate it, ask the printing company for something they have printed recently and the image data for it. If they give it to you, open the images in your image editing software like PS and compare the print to what you see on your screen.
Look onto your Photoshop CD. There has to be a image that is called “Ole No Moire.tif” or “TESTPICT.TIF”. Open it also.
Try to adjust your monitor. In Photoshop, open Edit->Color Settings and look at the Color Standards. There are some settings, the important ones are:

Standard for Europe
Standard for USA
Standard for Japan

Chose the one that applies to you. As RGB colorspace, chose AdobeRGB(1998) or sRGB. Both are usually ok. If you have a monitor gamut installed (your monitor is listed in RGB color spaces) you could also try this one, but I’d stick to AdobeRGB or sRGB.
It depends on you and your equipment how good the calibration turns out. Don’t rush it and DON’T TWEAK THE SEPARATION TABLES in the CMYK settings.

You can buy or borrow hardware to calibrate your monitor, but color calibration is something you must have done a few times and you have to know how a printing process works. It’s not meant for semiprofessionals, so don’t bother using it.

d) let the printing company make proofs of your images BEFORE they print. Do that until you’re happy/run out of money. If you’re not familiar with color correction, find a printing company which does it for you, let them make proofs BEFORE the print.
That’s the way every professional does it.

The proof fulfills two purposes: It lets you check your colors so you know that your data is allright and second it lets you check if the FINAL print is allright. Because also printing companies can do bullshit. Yes, this can happen. But if you’re a wise man/woman, you have a digiproof in your hand and you can slap it around their ears.

/edit: Here’s another link where you find informations about printing (you can also order calibration strips here)

FOGRA Graphic Technology Research Association

yours truly
fab


#15

yea I know most use Photoshop, which is why we kept shopping till we found a service that was professional and exacting. Don’t get me wrong, PS is fine for allot of work (Most work), but for us, when we have a client paying top dollar we deliver a product that is handled correctly from start to finish.


#16

Photoshop is definetely good enough for any print job, and if the results turn out shitty then it is because of the lack of knowledge of the person behind the computer, wrong color profiles, non-calibrated screens or bad prints, not the software itself.

The stories about ‘products being handled correctly from start to finish’ and ‘Photoshop being not good enough’ sounds like marketing nonsense to me.

But, I’m very interested how a so called ‘correct’ pipeline looks. Katie, can you tell me which programs are used in your studio for scanning, color correction, image manipulation and making images ready for print (when you are using the pipeline that handles everything correctly from start to finish) ?


#17

well if you can spot the difference between a cymk conversion done in scitex and one done in photoshop then i’ll gladly give you back the extra dollars your client and you like to spend

the gamuts are the same on any colour system, the curves are device dependant and the pixels all talk the same language

10 years of highend 3d and 2d print images behind me for international companies, and i’ve never run into a lack of quality with ps’s conversions…its usually the operator thats the problem

katie, i think you’ve been sold an expensive red herring


#18

You can do a picture in Maya, Max or PovRay. If you’re good, the picture will be good. You can use Photoshop to convert your pictures or DeBabelizer or some freakin’ hundredthousands-of-euro program you want. If you know what you are doing, it will be good. If you suck, the picture will suck. Agree?

Does anyone have more enlightening tips for the conversion of 3D images to CMYK or do you just want to rant about software? If you know a better way and a better software: fine. Name and explain it.

Katie, if you tell us that you will never use PS to convert you images, that’s okay. But please enlighten us what kind of “Professional conversion software” you use and how you use it.

It was -JT-'s ask for help which started this thread, so be helpful.

If we start a flame war here we should ask the mods to move this thread into the Photoshop forum where it belongs.
(Would be fine by me, I’m always eager to learn new things.)

:airguitar


#19

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