CMYK VS RGB Roland SG2-300

[swarnes]

Hi,
Attached is the colour I am printing,
The more solid one is RGB and the one with the black dots is CMYK, is this normal in printing, it just looks dark and not correct. The colour is off.
CMYK VS RGB Roland SG2-300
Please advise.

 

[jeff412]

RGB and CMYK will be different. We have found that RGB is usually the color that we want. However there is a lot more to color management than just picking the color you want. Corel and illustrator have color management settings that you should set up. Your RIP will have lots of color management settings that can greatly affect what colors come out of the printer. There are many color management videos on YouTube that can help. I highly recommend learning everything you can about color before you get too many files created. If not, you may find yourself correcting a lot of files years down the road, like we did.

 

[bteifeld]

The best way to specify a color is L*a*b*, or Lab. It is an
absolute specification of the color, because it does not
depend on a color space profile to give it meaning.
A good intro that explains this well is Ed Hagen's
Project BBCG- A Better Brand Color Guide, downloadable from:

https://www.projectbbcg.guide/wp-content/uploads/2023/01/How-to-build-better-brand-color-guides_v1.2.pdf

If you use an RGB or CMYK specification for a color, it is
meaningless without an accompanying color space profile.
In the colorful words of the book "Real World Color management",
this would be an image file that would be called "mystery meat".

An example of a color space profile for an RGB color specification
would be ProPhoto, as embodied in the file ProPhoto.icm. If you are
creating a design document, be it vector or raster, ProPhoto is
probably the best color space profile to assign to the document.
This also true of camera-originated images based on RAW files
which ultimately must be processed with a RAW converter into a
TIFF or JPEG file. See Jeff Schewe's book, The Digital Print, for more
about this.

If you are using a scanner as a basis for image documents, you need to
properly profile your scanner, and use the scanner profile as the color
space profile for your image document. This same concept can be applied
to cameras as a basis for image documents when the lighting conditions
are very well controlled, like in a studio setting. Xrite and Basiccolor are
two good sources of camera/scanner profiling software.

As a general rule, there is no good reason to use CMYK color spaces
in original documents that will be used in inkjet printing. This means
that you should never use CMYK specifications of color in documents
targeted for inkjet printing. For those situations where you have a
document that is based on CMYK specifcations of color- there are
many different opinions as to which color space profile you should use.

For files that are "mystery meat", you can use your design software to cycle
through some color space profiles to determine what may work best. This does
depend, however, on a properly calibrated and profiled design monitor that
meets or exceeds AdobeRGB as its reproduceable gamut. Gaming monitors
with sRGB reproduceable color gamut are not acceptable for color work.
Many laptop displays are sadly sRGB, so check your laptop display's gamut
spec.

If you are looking For color space profiles on Windows systems, they can be
found in the \windows\system32\spool\drivers\color directory.

 

[unmateria]

You need to calibrate everything properly with a spectrometer. Meanwhile, in illustrator make sure you are using srgb and not adobergb (enabled by default) and in export settings convert to srgb and embed profile.
But without an spectrometer, you are going to get just aproximations (with big deltas) loosing many time.

 

[damonCA21]

Looking at your values on that you are actually printing a slightly greenish shade of yellow ( the cyan element ) rather than pure yellow.

Printers that use CYMK inks are never the best when trying to print green tones, so what you are getting is pure yellow from the yellow head, then the printer adding small dots of cyan to try and produce the colour so it will look correct from a distance.

Because RGB is only using three colours, the printer has to convert this internally to CMYK as it obviously doesn't have red green and blue ink, so has to make them up from the CMYK inks. This can lead to giving a better result on come colours and worse on others.

 

[bob]

Every so often someone opens the gate and lets the coloristas out.

To answer your question, use RGB for bitmaps and CMYK (or RGB) for flat filled vector objects. Set your rendering intents to 'Perceptual' for bitmaps and to "No Color Correction' or 'Saturation' for everything else. Print a Pantone color chart for a reasonably complete chart of colors that you can print. If it's not on the chart, you can still print it most likely but not without seeming endless iterations in an attempt to get it 'just right'. Settle for 'good enough' and go about your life doing something other than obsessing about color.