Best results when changing RGB to CMYK

Report · Sep 21, 2007

Hi There,

How can I get the best results when converting a RGB to CMYK? For example, a tif visual when offset printing... Is there any programme, plug in, machine for this?

Many thanks

Report · Apr 24, 2019

It's easy, In Photoshop specifically. You save your edited photo as .psd file, then change the photo Mode from RGB to CMYK, but before this converting, you are asked to rasterize the image and flatten all layers, so you'll lose your original work and image. When the image is rasterized and flatten, then go again in section "Image" than "Mode" and change your RGB image to CMYK... without losing any colors!

Report · Apr 24, 2019

Sorry,

I am sure your comment was well intentioned but I am afraid you are mis-informed -

For the safety of other users, I feel I need to point out that the method you describe is a really simplistic and possibly even dangerous method of converting from RGB to CMYK

And its pretty rare that a conversion to CMYK will happen "without losing any colors" which you claim to be the result of using your "easy" method.

Why is Photoshop's "image/mode/CMYK" too simplistic?

- because relies upon 2 settings which a user may have never even looked at:

1: the default CMYK profile selected in Photoshop's "color settings".

This is often not the right CMYK profile for the current print job.

CMYK profiles are totally specific to the print method and substrate, there are NO good defaults w that work for everything.

e.g such conditions as Coated or uncoated paper - sheet fed or web press or even newsprint perhaps?

you can read more here: color management / colormanagement : about icc colour profiles

When sending a letter you'd never use a default ZIP code, do remember that CMYK needs the right coding too.

2: the default rendering intent in Photoshop's "color settings".

Controlling the rendering intent during conversion can provide better results that relying upon a default.

in Photoshop's "convert to profile" action is the safe way to do this conversion.

I hope this helps

if so, please do mark my reply as "helpful", so others who have similar issues can see the solution

thanks

neil barstow, colourmanagement

Report · Apr 24, 2019

HI ashokcool2636,

I am glad you found my reply helpful

thanks

neil barstow, colourmanagement

Report · Jun 11, 2019

If you cannot get these details, Miss Sparkles, you are in trouble, and need to take action to protect yourself from fallout. One method is to make sure of real printed proofs. It may suggest that people involved are not very picky about colour (designers often have much higher standards than the client), and you could choose to go with industry lowest common choices for your country.

It won't be a question of the print house "not thinking to change them to CMYK". That will happen in the printing process, one way or another.

Report · Jun 11, 2019

In any properly set up modern RIP (output device for professional printer) you can send tagged RGB (RGB with an ICC profile). The RIP will do a job as good, perhaps better, than Photoshop. No knowledge of CMYK profiles is required.

So you only need to send CMYK for people with old equipment, or equipment not set up correctly, or people who - despite their equipment working well - use out of date checks. Unfortunately, this covers a lot of printers...

Report · Jun 11, 2019

Hi Test Screen Name,

That’s a point, in RIP conversion - and it often works fine.

In fact it's the default process of a modern "late binding"workflow where the PDFs are made in RGB and conversion to CMYK is automated down the line based on printing use.

However, I like to teach my clients (many of whom are photographers) that’s its worthwhile taking control of the conversion from RGB to CMYK manually, creatively, on a file by file basis.

- That way the colour and tonal compression issues sometimes associated with conversion to CMYK are often avoided, such as the dreadful purple skies we've all seen in print. A bit of judicial editing to saturation of severely out of gamut colours in the RGB file can often smooth an image's way through the conversion to CMYK and into the world of offset print.

Also choosing between relative Colorimetric and Perceptual Rendering Intents for CMYK conversions can improve results,

there is no sensible overall default for Rendering Intent.

Even if a photographer or designer is going to send out an RGB file in the end, it can still be worth doing the above judicial edits to saturation [as preview to it's eventual conversion] to ease the images way through the bottleneck en route to offset print.

I hope this helps

if so, please do mark my reply as "helpful"

thanks

neil barstow, colourmanagement

Report · Jun 11, 2019

If I get the colour management spec (is that what it's called?) and the PDF spec from the printer, could you help me make sure I have set it up right for them. Would really appreciate help on this.

All this talk of colour set ups has worried me greatly, I'm just amazed that my previous jobs have printed correctly when I have been seemingly not doing it correctly? Arggghhhh!

Report · Jun 11, 2019

Hi Neil,

So I've read all of the above and think upon reading your information I will link my RGB images to my InDesign document.

Can you tell me what I am asking the printer for? If it is just the PDF spec, how do I, when exporting the PDF to that spec, export it with all the images as CMYK should they be required in CMYK need to please? I have looked through the PDF options and I cannot see this as an option?

And if I'm not changing the images from RGB to CMYK myself (as I think it sounds way too complicated to do it without knowing exactly what options you're selecting and not selecting, Id hate to mess up the jpgs) I don't need to worry about the colour management side of things do I, I can let the print house do that?

It's all gone a little quiet and I really need some help on this if anyone can help please?

Report · Jun 11, 2019

Hi Miss Sparkles

If you don't plan to make the CMYK conversions, then, yes, you just need the PDF spec. and follow those instructions carefully.

Only the people receiving your file can tell you the PDF spec. needed. The magazine publisher should have that information.

If the images are required to be in CMYK then you need a CMYK ICC [print] profile relevant to the publication - I would suggest using Photoshop's image/mode/convert to profile to do this conversion so you can see what's happening on your calibrated display screen.

Your screen is calibrated I hope, if you are making important judgements about appearance on it?

You may want to read up about the Rendering Intents available for this conversion (basically 'Relative Colorimetric [with black point compensation]' - or 'Perceptual' are the two options you'd choose from.

Here in the UK there is a magazine manufacturers group which can, I believe, provide submission guidelines for their member publications, you may find something like that Stateside too.

I hope this helps

if so, please do mark my reply as "helpful"

thanks

neil barstow, colourmanagement

Report · Jun 12, 2019

Hi Miss Sparkles

I could help with the colour, but that’s reasonably straightforward once you have the spec.

Rob Day is your man for help with PDF, why not ask on the Indesign forum

Report · Jun 12, 2019

Thank you.

So, if I am changing the images to CMYK the colour profile to set up should come from the print house?

Report · Jun 18, 2019

In the ideal world your colour setup instructions would come direct from the printer, if that is not possible your colour consistency is nothing more than pot luck, however sticking to recognised standards such as FOGRA39 (coated), FOGRA29 (uncoated) etc would be your best bet if you have nothing else to work with.

But lets not forget with all the good preparation and setup the colour of the end printed product is in the hands of the Pressman running the actual job and how good he/she is achieving the intended targets (and how good their foreman is at checking its to standard).

Ultimately the best advice is to do some research and find a print company that has a good reputation and one that prints to recognised standards.

Report · Jun 19, 2019

Excellent, thanks so much Andy.

After all the checking and making sure I was doing the best I could for an optimal result in print, it turned out the client actually wanted to take my A5 InDesign file (as a PDF) and insert it into PowerPoint to get it professionally printed!! At that point, I explained to him that I couldn't be held responsible for how the job would print and just sent my packaged InDesign file to him instead. Apparently, he did send the PP file to the print house and not the InDesign file so I can only imagine what the end result will be. I have never been asked to send a PP doc to professional repro before!

I have been working in design many years but have often found it very difficult to get the PDF spec (and now I guess that will include colour spec) from the print house, does anyone know why this is such tricky information to get from a print house or is it just the difference between a good, reputable print house and a not so good print house? I'm just so intrigued as to why there seems to be a big mystery around this info and I'd love to know why.

Report · Jun 11, 2019

So, if I've got CMYK jpgs in my InDesign document (the jpgs were changed simply from RGB to CMYK in Photoshop and Illustrator, this is the way I have always done it and didn't know it was wrong) and want to PDF my artwork (once I hopefully have PDF specs from my client's printer) would I be better off going back to the original jpgs (which are RGB's) and linking those instead of the CMYK version and then send the PDF to the printer, or do I change them to the new way of changing all the images from RGB to CMYK (if I can understand how to do it) and send the PDF using those JPG's instead?

I'll be honest, I'm totally confused and this job has got to be at the printer's by Friday, so now I'm a bit stressed!

Report · May 16, 2024

I've always had good results using the image>mode>cmyk method and then correcting with selecting colour as per the below video:
https://youtu.be/V3oCJTbWblw?si=5BNDjf1KX6b1VYRp

Report · May 18, 2024

@crispincorky ::WORKING IN OR CONVERTING RGB TO CMYK::

Generally I would advise that there is significant opportunity for error when converting to CMYK unless some thought is applied to the process.

When simply choosing image>mode>cmyk the default CMYK ICC default profile [as selected in "Color Settings"] is used. IF that default profile relates properly to the print condition that’s the destination for the files then that's OK. [usually CMYK data is prepared for an offset or digital press].

BUT, many users simply take the advice to use image>mode>cmyk without checking whether the default CMYK ICC profile is the right one for the print destination in question. That can lead to some pretty unsuitable data going to press and, thus, a disappointing print run.

::INKJET PRINTING::

Unless preparing files for an inkjet winter driven / controlled by a RIP, then the pipeline that’s used for the data converts from CMYK back to "whoknowswhat" RGB before printing. ALL inkjet printers I know of, unless RIP driven, are far better treated as RGB devices. Taking data from RGB via a press CMYK might needlessly reduce colour gamut - so, will potentially reduce saturation in areas that could have been fully realised had RGB data been sent to the printer driver software. Inkjet printers tend to have colourspaces that far exceed the CMYK press ICC profiles installed with Photoshop

I hope this helps explain my position on working in CMYK colourpace
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management
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