# Why are we told to design in RGB?



## InfaRedd (Aug 17, 2011)

Hello, 

this may be a silly question, but why is it said that you should set your colour settings in photoshop to RGB when we print in CMYK, the CMYK colours can never be as bright as RGB on screen so is there much point in this, as some design can look great on screen, but come out dull looking on the shirt.

Also is there anyway on photoshop that I can create pure CYMK...I'll try to explain....

Basiclly I tried to get a pure yellow colour in photoshop, so I in my colour picker window I changed yellow to 100% and all the rest (cmk) to 0% but when I click on the yellow with a colour picker it shows that my yellow is 100% and there was always about 5% C in there and and sometimes 1% M, and when printing you can see th 5% Cyan coming through.

and the same applies for all the colours, you can not get pure 100% c,m,y or k!

Thanks for your time


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## treefox2118 (Sep 23, 2010)

The biggest reason why we "need" RGB files is because most RIP technology only has RGB color mapping. It knows what colors of CMYK it will output based on RGB values.

Some RIPs in the wide format world also support CMYK inputs. Most likely, most current DTG RIPs could handle a CMYK color table, too, but that would require more coding and testing.

In my wide format department, we can take two totally identical looking RGB and CMYK files and print them using different input ICC profiles, and the output will be as much as 25% different!

One thing you can try to do is design in RGB, convert to CMYK in Photoshop, and then convert back to RGB before saving. See if this helps you get a more consistent screen-to-print result


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## dot-tone (Jun 19, 2008)

I do not dispute what Treefox says. I will only add to that.
Not listed in order of importance.

1, We (as an industry service provider) receive art files from many sources. One important source is another design house. They will most often refer to pantone colors when creating art. This is not to say that all customers want PMS matches but some do and this part (for those who do require matches) Keeping the art in RGB is critical. This allows your DTG rip to do it's job. If we were to make adjustments outside the DTG preferred settings (inside photoshops color settings for example), results wold be unpredictable as they tend to conflict with the DTG settings. This more so involves people who want to match the original art as best they can. Many DTG owner just load the file and print. However it comes out is what they get. Thats ok also, if that fits your business model.

2, Again connecting the process with pantone colors, creating your art in RGB with vibrant colors or not, is closer matched in print when compared to many of the PANTONE colors. Pantone has specific ink formulations that can be achieved in print using these custom colors. Many will more more accurate to RGB colors used (when compared to CMYK color conversions. You've heard before that CMYK can give you many many colors, but also is limited in the window of available colors in print. It it does not allow for colors that are way outside the gamut. The link here has a good image example of pantone gamut and CMYK gamut.

MMP - Print Design Mail: Color Theory & Color Profiles

Added to the discussion of color gamut (as seen in the above image example is the RGB color gamut and the human eye gamut. Our eyes are capable of extending far beyond what can be printed or even seen on screen in RGB.

When you leave your file in RGB, you are more so allowing the DTG RIP to do it's best. If you were to convert to CMYK, you are 1st stripping out potential color than could be achieved in the DTG print process. 2ndly, your specific settings inside Photoshop can potentially compound this result.

If you design or create the art in CMYK, you are more accustom to the color limits. A take away of this is that you are not reaching your full potential in image vibrancy.

Have you ever wondered why screen printers will print a 10 color simulated process print over only 4 colors in CMYK? The reason depends on the job request. If you do not own a DTG printer and are only doing 200 white shirts, with full color art, then you may want to screen print it using CMYK (if the customer is not that picky about the image).

If it's for a larger production run, while they will use more colors, in setup and production time, they may choose to do sim process to *A*, be more consistent with the printed image during longer runs in production and *B,* to reproduce the image more accurately. I'd guess that for medium to large volume shops, 95% or more of multi color images are ran in simulated process.

All of this applied to both DTG printing and traditional screen printing. Most screen printers know to start out creating the art in RGB.

As I touched on above, is the fact that once you convert (from) RGB, to CMYK, your additional color data (the wide gamut) is stripped out and _cannot_ be added back in once converted. The idea of converting back to RGB becomes fruitless.

Lastly, RGB files provide a wider option of editable filters and effects that you might apply while designing. A CMYK file will also allow you to still use "some" of those filters and effects but have slightly different results. Additionally, once you convert to CMYK from RGB, some of those filters may still be there for you to use, but are no longer _editable_.

Getting into color setting and how they play a part is yet another lengthly discussion.

Bottom line? Keep your files in RGB and you can't go wrong. Wider printable color options and wider range of tools to play with inside Photoshop. Since I put so much into this post, I think I'll keep a copy for my blog. 

Dot-Tone-Dan


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## InfaRedd (Aug 17, 2011)

Thanks for all the info, I think I'll stick with RGB then, but I still seem to have the issue of being able to print pure colours, when I do a test print threw my rip software the printer will print pure cmyk, but if I try to do that in photoshop it wont let me, theres always a percentage of other colours in there.


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## PositiveDave (Dec 1, 2008)

RGB has smaller file sizes - it has three rather than four channels.
It has a bigger gamut, at some point we need to convert that to CMYK but it makes sense to do it at the last moment - by the RIP because it is possible to lose more gamut than is necessary if an imperfect conversion is done. PS will generally not be using the same profile as your printer.


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## dot-tone (Jun 19, 2008)

Going against what I just posted above, this is a unique situation.

To make an isolated area solid Cyan within nothing else in it, Do that in the CMYK (master channels) . Like for-instance, if you were to create a square, go to the channels window, select the master channel (the top one that previews all together) and fill in 100% solid cyan in one area. Repeat for other colors in other isolated selections.

This is doing what you want manually.

In this case, you would want to convert to CMYk first, and let adobe's settings do what they will, and then manually fill the selected are to be 100% solid Cyan (after the fact), forcing it to work after you've converted.

If the DTG rip changes it and adds in other percentages, I can't help there.


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## cavedave (Dec 5, 2006)

We supply RIPs to a number of the manufactures and there is no problem printing RGB or CMYK, there are always pros and cons to both, some people swear by RGB while other CMYK.
RGB has a bigger color gamut, but as the T-shirts have a very small gamut it doesn't really make a lot of difference and if you setup your color management either should work well.

The contamination you get of other colors in areas of pure Cyan are caused by the ICC process (as it trying to match a color) and not all Cyans are the same.
Normally there are ways of setting up exceptions for this in the ICC process and work best in CMYK.


Best regards

-David


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