RGB and CMYK Monitor Calibration!

deemarie · October 17, 2005 9:10 am

I have written a number of articles on color over the years. This is updated as of 2005. I started working in the field of graphics before color profiles even entered the arena. I remember when many programs, such as Adobe Illustrator, used manual calibration to calibrate the monitor inside a specific program. I wish many of these programs still had that as an option, because many pre-packaged profiles simply don't work. For example, I have two Viewsonic Professional Series P95 f monitors, and two P95 f+ monitors. None are exactly alike. This is normal for a monitor. Thus, if I only used a pre-packaged profile, and didn't tweak each a little differently, it wouldn't do me a lot of good. Plus, as the monitors age, their color will change. To create a correct profile, I would have to use special equipment; and I do not mean just the color calibrating software that comes packaged with many monitors. Let me first state something that is unfortunately true. The same printer or scanner with the same driver version on different operating systems will produce different colors. This is a real problem. For example, I had my Epson 1280 adjusted under Windows 2000 to my satisfaction. No matter what I do, it will not interpret color correctly under Windows XP. Here is how I use the tools available to me at home to calibrate my monitor. This method has worked for me for years even though it has changed slightly as the programs have changed. I will use Photoshop CS2 to demonstrate. However, this works in other programs since it is program independent. I am working in RGB. However, at the end of this discussion, I will note some facts about my experience with CMYK in this home type of environment. The first step is critical. The monitor must be able to produce a neutral gray screen. Here is a way to tell [if you use a PC, don't use fancy wallpaper] go to: property>appearance>desktop>advanced.
To know if the gray is correct, get an outside source like a photographic 18% gray card, or any medium gray card that is absolutely neutral gray. If your screen is not neutral gray, your colors will always have a cast to them. If you need to correct your screen, use either the software that came with your monitor or with your video card. I am not talking about calibrating your monitor; all I am recommending is that you make your monitor screen a neutral gray. Once you do that, the colors should line up properly. At least, I have never known them not to unless your monitor is overly bright or overly dark or just plain bad. This is not scientific. After years of doing this, I can tell in my gut what I need to do. These are just hints I am sharing to help you get there. I cannot tell you if your monitor is too light or too dark. We all work differently. That is why we choose different profiles. The same color profile will appear differently on different monitors especially if the brightness levels are different. Having the light in your room at a medium brightness and not shining directly on the monitor is also important keep it consistent. I will detour and discuss light now, since it will be important soon. Light is many difference colors. Daylight has more blue in it than does a normal incandescent light bulb. When I am looking at color swatches, for example, I am looking at them under a medium light and near my monitor, which projects a different light. There will be some difference in color between the swatches and those on the monitor because of the reflectivity of the printed paper, and the differences in light. However, the difference should be minimal. If I were working near a window, there would be another difference in color. If you look at a print under a regular light bulb, it will look reddish. Under some fluorescent, it will look green. If there is a black and white grayscale in it, the gray should be a neutral gray under mixed light daylight plus incandescent. I have found that at home the best way is to take a print, or anything that is in color, and look at it near a window as well as a table lamp. We are neutralizing the light to some degree. Again, we are not being scientific, but I have found this method produces good results. Learn to look at colors and see how they change with lights. Once your monitor is a neutral gray, then you can go into your individual programs and choose a color space to work in. In the last two versions of Photoshop, I have used the same RGB color space, sRGB IE 661966-2.1. I have found that space most accurately represents my colors on my screens with the way I have set up my overall monitor, i.e., intensity of light and neutral grayness of the screen. I have created a montage of images to use as a reference. This montage is comprised of Trumatch swatches and pictures of objects I have at home, as well as two images I created. I first created little boxes to be filled in by a Trumach color. In Photoshop I double clicked on set foreground color and then clicked on color libraries.
Message2438792.jpg Message2438793.jpg
From there I accessed the Trumatch library. Once there, I typed in the letters and number; like 6a for red and proceeded from there.
I could have used Pantone or any library where there was also a separate book of swatches. The gray scale was just a matter of typing in 100%, 90%, etc. using grayscale as my color mode.
Since I am not working with a service bureau and needing to produce color separations, I work in RGB mode and leave the default setting for CMYK alone. To decide on the appropriate RGB color space, it is important to turn off embedded profiles at this point, even if you decide to use them later. If you don't, your images will not change in color as you change RGB profiles. I then checked all the profiles available in Photoshop and compared them to the swatches and the colors of the other external sources I was using as a test base.
I kept a list of the ones that most closely resembled the swatches as a whole. It is important to use mixed-colors (those under the gray scale in the image above), because I have found that it is harder to tell the saturation level of the RGB, CMY colors if they are the only ones used, and that can make a difference. When I first started, I only used those colors. Then, when I went to print, the colors were not correct. It was because of the saturation levels. A color that looked OK on the screen could be too saturated and overpower another. Usually what you will find is that one color might be off a little, and in trying to fix that by choosing another profile, others will then be off. So, go with what looks best as a whole on your monitor using the swatches as well as all the objects. While I did all the above testing in RGB, I took a blank template and made sure it was in CMYK color mode. I then went through the process of filling in the swatches in CMYK mode, and brought in the bottom images, which converted them from RGB to CMYK. I looked at them on the screen beside an RGB test and an RGB test that I converted to CMYK. The images of figures and pictures were all originally created as RGB so even in the document created in CMYK mode, those images had to be converted when copied and pasted. All the color and gray scale bars in first image to the left were created in CMYK mode. The bars in the middle image were created in RGB mode, and those on the far right were created in RGB mode and converted to CMYK mode. A screen capture was taken of each image. There were no embedded profiles.
Next we need to look at the relationship between the different colors and what they mean. The relationship between Red Green Blue and Cyan Magenta Yellow blacK, is often hard to understand. Both color spaces are interrelated.
Notice how, no matter what mode you are in, the colors created using CMYK percentages will always appear the same. When you create colors using RGB, as you add them together you get white. When you remove all color, you get black. In the chart below, assume that for RGB, when you are creating new colors, you are adding together 255 of each color. In the CMYK section, you are adding 100% of each color to create the new color.
However this is all theoretical. In the real world, it does not happen that way; and that is part of the problem and confusion about colors. Look at the screen captures from Photoshop CS2 mixing palettes. These were created in RGB color mode. Look at the RGB and CMYK boxes only. The top line shows colors made using RGB numbers. The second line shows colors made using CMYK numbers.
The same holds true for the next group of colors.
RGB colors are colors from light think in terms of the light from your monitor while CMY[K] colors are colors from ink think in terms of a printer. In light, if you add Red, Green, and Blue together you will get white light. The absence of all colors is black. Whereas in CMY, it is a building up process, Cyan, Magenta, and Yellow added together create Black [dark mud brown], and when all are taken away, you are left with white. Since the back is not really black, we add blacK to our CMY printing colors. In very simplistic terms, and without going into any scientific explanations; one works in an RGB [light] space, eventually using CMYK colors if the documents are to be printed. If the mode is RGB or CMYK, you are still using the printers [CMYK] colors if the end result is printing. The web has other problems, which I will not even try to discuss here because this is a discussion of RGB and CMYK color modes and not Indexed color.
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  • The Paula Sander's Report is a regular Renderosity Front Page featured column, where Paula investigates and comments on graphic software, techniques, and other relevant material through her reviews, tutorials, and general articles.
October 17, 2005

Article Comments

CorwinRathe ( posted at 12:00AM Mon, 17 October 2005

A good way to remember the two is RGB is a additive color system and CMYK is a subtractive color system using the four main process colors used to print with. RGB also has a much larger color gambit or colors it can reproduce then CMYK does. Although there are colors in each color space that the other can't reproduce the same.

Paula Sanders ( posted at 12:00AM Mon, 17 October 2005

There will be more articles in this series. The next will be on "Resolution" and, then, after a product review, one on the Epson R2400 and one on calibration using hardware and software.

deemarie ( posted at 12:00AM Mon, 17 October 2005

I am so excited about this series Paula, I know I can hardly wait until next week :] Dee-Marie

Dall400 ( posted at 12:00AM Tue, 18 October 2005

This is a good series for someone like me, who has never understood cmyk color, has always used RGB, but has always had prints come out either dark or a bit faded! Although my monitor calibration at the moment is good, this is always good info to have access to! Thanks, and can't wait for the next articles! Cheers, Jesse!

Gongyla ( posted at 12:00AM Wed, 19 October 2005

I always read your articles, but this one leaves me baffled. No monitor can ever display CMY. It can fake it in the best of cases, but never attain the real thing. As for RGB: some monitors can indeed display sRGB, but these are exceptions. In case they can, it's usually written in huge letter on the cardboard box in which they are sold. CMY is only useful for offset-printing and some -very rare and exceptional- cases of deskjet printers. Either these come with a profile of themselves, or you have to create one yourself. Calibration means that there is one strict and exact norm to which all can be adjusted. This norm exists and was created by a joint effort of Adobe and the CIE. A profile means that for every colour a comparison with the standard (calibration) norm is created and the difference between the norm and the real value is added to a list. For example: "This should be 128,128,128 but on this device it is 128, 132,129. Therefore we must adapt accordingly." And, in case you use Photoshop, why not use the Gamma utility that comes with it to calibrate your monitor? When working for print, it is adisable to use the AdobeRGB and not sRGB as the first one encompasses many hues that CMY can produce but that you cannot see in sRGB. Hence the big problem many people experience when they have something printed. These and many more suateions arise when reading your article.

Paula Sanders ( posted at 12:00AM Wed, 19 October 2005

Gongyla - I am really glad you read my articles, and I am sorry if you did not think I was clear in certain parts. Firstly, I never said the monitor displayed CMY. In one part I distinctly wrote that: "CMY[K] colors are colors from ink think in terms of a printer." Also, you will notice I am speaking of RGB and CMYK mode, just as Photoshop does. Secondly, I am not speaking of only calibrating your working space within Photoshop, but your monitor as a whole. Before profiles, calibration was done by manipulating the colors until the screen looked "good." If I remember the version, Illustrator 4 or 5 still used that method very satisfactorily. I don't use the Gamma because I didn't like its results when I tried it years ago. Maybe it is better now, but my system works by judging from my workflow. In a few weeks I will be able to judge further since I will be runnung tests using specific software and a colorimeter and writng about the results.

CorwinRathe ( posted at 12:00AM Wed, 19 October 2005

Colorimeter's are a excellent tool for calibrating your monitors. To really build good printer profiles use should use a spectrophotometer. Color management is miles from what it used to be, but it's important to remember even with te best profiles it doesn't give you a perfect match. The main thing color management does for you is preserve the realtionships of colors and move colors into the correct color space that are outside the color gambit of the output device that you are using to print with. Enjoyed reading your article, you have some interesting stuff. I think your article on resolution will be helpful to many. People often have problems with it when they first get started out.

novelist999 ( posted at 12:00AM Fri, 21 October 2005

I can't wait for more articles on this subject, because I recently got a top of the line Sony monitor, but I've not been happy with the way images look on it. I've struggled endlessly trying to callibrate it. Thanks so much for these articles. I'm sure they will help. :-)

Paula Sanders ( posted at 12:00AM Sat, 22 October 2005

Well, I am in the process of testing the MonacoOptix colorimeter. I have not used any hardware to calibrate my monitors since I have always been satisfied with how I did it myself, but I felt I needed to do this for this series. I will start this coming week and it will be a few weeks before that article comes out. But I am excited about this myself. I have really loved the responses to this first article in this series and they spur me on to write more. Thanks a lot.

nickcharles ( posted at 12:00AM Sun, 23 October 2005

Excellent article, Paula! This series is of special interest to me, as I am taking on a project that will eventually go to print. Can't wait to see the rest of this series :D

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