Out of Gamut

[CES020]

I've been trying to become educated on color by reading as much as I can, and by attending any seminars around by anyone teaching anything about printers and color. Having said that, on a scale of 1-10, 10 being educated, I still think I'm a 1.

It's been quite confusing (understatement), as some people saying "Design in CMYK only" and then other's say "RGB only" and then others say "It doesn't matter, the RIP's going to handle it. I've seen well respected people say completely opposite things fairly frequently.

My question is about trying to understand the gamut of a printer and how you know something is outside the gamut of your printer. In Illustrator, there's the infamous little hazard sign when you pick a color, telling you that the color selected is "out of gamut". Out of what gamut? I assume it's the color space you are working in. RGB, having the larger gamut than CMYK, I understand that it's saying the color you have selected is outside of, let's say "Adobe 1998 RGB" gamut. However, what good is that data to me, other than knowing I'm outside of Adobe 1998 RGB? That still allows me to select a color that's INSIDE of Adobe 1998, but still outside of my printer's gamut.

It seems to me that I should have something loaded in the color settings that relative to my printer(s), which then, would be a real indication if the color selected was out of gamut.

Anyone care to tell me if I'm thinking about this right, wrong, or where I'm confused? I'm just trying to understand it better.

Thanks!

 

[SightLine]

You are correct in that yes you can create a printer profile to load that your programs can use as a reference to what is within the printers gamut. One thing to keep in mind - the built in CMYK profile in Illustrator, Corel, Photoshop, etc. is not even remotely close to the capability of the CMYK inks ink your printer. The CMYK inks you run have a far greater gamut than the default CMYK design profile.... This is why you see many suggest that you design in RGB (Adobe 1998 profile or even sRGB). This way you have a much greater color range than if you were to design in CMYK (using the default web coated SWOP profile). I'm not sure why but many insist on designing in CMYK with that profile thinking that CMYK is CMYK is CMYK which is far from reality. Now, if you want to get a full i1 setup with the full software package then you could profile your printer and create a full blown CMYK profile that is specific to YOUR printer and inks then add that into Adobe Bridge (which will make sure it is consistent across Illustrator, Photoshop, InDesign, etc). Then if you design with that custom CMYK profile you will be working specifically within the gamut your machine and its inks are capable of. That being said - that specific profile will be for one specific resolution, heat setting, passes, and particular media. It would be very complicated and time consuming to make a special profile for every single media and resolution combination.

So for use anyways - yes we have several custom profiles we have made specifically for our printer/ink using FlexiSigns built in profiling. However we design in RGB (Adobe 1998 profile) and let the RIP deal with the times where colors might be out of range. Using "perceptual" rendering intent in Flexi generally gets the out of range stuff "close enough". There are always going to be some colors that you are just not going to be capable of getting close to but I've found that it is very rare that you cannot get close enough.

 

[DIGIXTRA]

I've been trying to become educated on color by reading as much as I can, and by attending any seminars around by anyone teaching anything about printers and color. Having said that, on a scale of 1-10, 10 being educated, I still think I'm a 1.

It's been quite confusing (understatement), as some people saying "Design in CMYK only" and then other's say "RGB only" and then others say "It doesn't matter, the RIP's going to handle it. I've seen well respected people say completely opposite things fairly frequently.

My question is about trying to understand the gamut of a printer and how you know something is outside the gamut of your printer. In Illustrator, there's the infamous little hazard sign when you pick a color, telling you that the color selected is "out of gamut". Out of what gamut? I assume it's the color space you are working in. RGB, having the larger gamut than CMYK, I understand that it's saying the color you have selected is outside of, let's say "Adobe 1998 RGB" gamut. However, what good is that data to me, other than knowing I'm outside of Adobe 1998 RGB? That still allows me to select a color that's INSIDE of Adobe 1998, but still outside of my printer's gamut.

It seems to me that I should have something loaded in the color settings that relative to my printer(s), which then, would be a real indication if the color selected was out of gamut.

Anyone care to tell me if I'm thinking about this right, wrong, or where I'm confused? I'm just trying to understand it better.

Thanks!

I hope this can help you to understand the theory a little bit:
1/ People tell you to use CMYK or RGB or mixed color spaces... are technically right if you have an ICC workflow in place. The one that asked you to use CMYK is a little bit on the conservative side. Think of it this way... If your printer is a C,M,Y,K,LC,LM, LB printer but I ask you to print using only CMYK. You still have an OK print but you know that all the light color is just a watse.
People tell you to use RGB or mix of color space is the one that is using ICC workflow. The Rip can only handle 2 imbeded profiles at a time (be it CMYK and RGB). If you have multiple profiles better to let the software such as Illustrator, Quark express to handle it.
2/ Common mistake that people tell you RGB has a bigger color space than CMYK...technically this is not correct. Both of these color spaces are device dependent. This mean each device can give you different color gamut - think of all the TV that are on store display will give different red even they are all RGB devices. In one color space it could give you a better gammut than the other. For example RGB give you better blue but CMYK will beat the RGB on the green side. For this reason ICC engine has to rely on the independant color space such as LAB and use this as a reference to convert color between spaces.
3/ To know which color is outside of your printer gammut... you need 2 things:
a) Profile your printer using popular device such as Eye1.
b/ Once you have the ICC of your printer generated, you can bring it into Photoshop and open the file under this profile. Photoshop will show you which color is out-of-gammut.

Hope this would help..Sorry for my English.. it is not my "forte" and you may have a little hardtime to understand.

 

[P Wagner]

In order to answer the original poster's questions adequately, we need to understand a few basics:

1) Large-format CMYK printers that are driven from a RIP are considered CMYK devices in the color management arena. By way of contrast, desktop color printers are usually considered RGB devices, in spite of the fact that they often use CMYK ink or toner as their colorants.

2) Most RIPS are attempting to leverage the ICC-based workflows. See www.color.org for more information on the ICC.

3) ICC-based workflows are intended to reproduce the color in the file, across the myriad of devices in the modern workflow, including displays, scanners, digital cameras, and printers. Each of these is inherently unique in terms of it's gamut.

4) CMYK and RGB do not represent gamuts. They are color models used by physical devices the digital workflow.

5) Gamuts are based on the behavior of a given device, in a given state (calibrated or uncalibrated).

6) Embedded Working Spaces are an ICC construct designed to provide standardized meaning to RGB or CMYK values (numbers) in files. US Web SWOPv2 is the most commonly used CMYK working space in North America. sRGB is the most commonly used RGB working space worldwide. Graphic arts professionals often use the Adobe 1998 working space.

The attached image displays the relative size of SWOP (white boundary), Adobe 1998 (red boundary), and a custom-built media profile for the HP Latex 260 when printing on 3M IJ 35c vinyl media. Note that the SWOP boundary is almost (but not quite) entirely enclosed by the custom IJ35c boundary. This means that a CMYK job file set-up to use US Web SWOP will never contain the colors outside of the white boundary, and the printer will not produce anything outside of the white boundary, in spite of the fact that the printer is perfectly capable of producing colors out to the multi-colored boundary.
On the other hand, if an RGB file is set-up using Adobe 1998, it can contain everything inside of the red boundary, which includes tons of colors outside of the printer's ability to reproduce in place (multi-color boundary). In this case, the RIP will re-map those colors to end-up inside of the multi-color boundary, but will give us all of the color that the printer is capable of when printing onto that media.

Hope this long-winded explanation helps with these concepts.