This subject is one that has frustrated photographers and print makers for years. We hope to shed some light on the subject and remove any stigma of “black magic”. Everyone knows it’s important, but can you easily learn color management to make better prints? Most of our clients have become comfortable learning how to use color management software to their advantage, and we believe you can, too. Let’s get started.
There are three color spaces you should be aware of to effectively manage color:
- Image input (camera) color space
- Monitor color space
- Printer color space
A digital image must be linked to a color space in order to be viewed and printed. This color space is defined as an ICC Profile, which is a file that, when attached to an image, structures the image color characteristics into that space. When you open an image in Photoshop, the image is viewed through the color space chosen by you or Photoshop. The appearance of Photoshop is controlled by the monitor profile, and when the print is made, the image color space is converted to the print color space. The various color spaces are all linked together.
Color space in this discussion relates to the amount of the visible spectrum applied to an image. Look at the color profile Adobe 1998 ICC Profile and see the coverage of the color spectrum below. You see the outer structure of the universe of color and there in the middle is how much of the space is being applied to the profile. Adobe 1998 is considered the most popular color profile for photographers and is said to be a very wide color space for images. This does not mean that your image actually utilizes the entire space. Most photographers hardly use the entire color space.
There are numerous color profiles that have been created for different reasons. Each of these profiles covers a specific amount of the spectrum, which is shown below in the charts. Below are just a few of the color profiles used. They illustrate the different spectrum that they encompass.
Image Input Color Space
The color space of a digital capture file is portrayed in RGB (red, green, and blue). Therefore, the profile that will be used to describe that image will be an RGB profile just like we described above. Input profiles offer the largest space of the three color spaces. This brings up an issue: If the input image offers a greater color spectrum than the monitor, how can I view my images accurately?
Most image do not utilize most of the color space and can be portrayed accurately in spite of this, but there are images that go beyond the monitor color space. So should we use a very wide color space for our original, or should we compress the image to a smaller color space that can be viewed and printed accurately?
I would not convert the image if it were going to be printed via inkjet. Evolving technology allows inkjet printers to reproduce a wider and wider segment of the color spectrum. However, if the image is to be printed via printing press, you may want to compress the image for the printing company. We will be discussing the importance of soft proofing, which will explain how to view the relationship of the image profile to that of the printing profile. This is an extremely valuable feature Photoshop offers. This means that you will be able to see how the image will look before you print it. If a color cannot be accurately reproduced, you will see it, but it is important that the monitor you are viewing the image on is calibrated correctly.
Monitor Color Space
A monitor, by its structure, is an RGB device. This means that all the colors you see are made up of red, green, and blue. A good monitor is supposed to portray millions of colors, but does it? Let’s look at a high-end monitor profiled to see its spectrum.
You can see that the monitor color space doesn’t cover the entire spectrum, but instead only a portion of the color space is covered, not any greater than the Adobe RGB 1998. In fact, Adobe 1998 RGB extends in areas of yellow and green beyond the monitor’s profile. If this is a profile from a top monitor, should we not expect less from a less expensive monitor? Actually, not too much lower. That’s the good news, but there are other reasons to buy a good monitor discussed elsewhere. Remember, all monitors are not created equal, nor are they necessarily accurate. They must be calibrated to accurately portray the output viewing conditions of color temperature and brightness. If the image is viewed on the monitor set at 65K (daylight) and the output image is viewed under warm lighting, this mismatch will cause you to improperly color correct.
It is also important to understand that a monitor transmits the image, while the output print reflects the image. Transmitted images are more lively than reflective images. So unless you create accurate profile between the monitor and output, what you see is not what you get. To purchase a monitor spectrophotometer, go to monitor calibration.
After you captured the image you want to view it on your computer monitor. As you can see from the above profiles, the color space of a monitor may not reach the color space of the input profile. So it is important to choose a monitor that can be calibrated to offer the widest color space.
Let’s discuss a little bit about monitors. I have said that not all monitors are created equal. We are now looking at images on LCD monitors and most of them are made for gaming. The few that are made for graphic applications, such as Photoshop, are more expensive. These monitors, such as LaCie and Eizo, have color control built into the monitor. They are capable of storing several configurations. To create a monitor profile with other monitors that do not have built-in calibration, Xrite’s Gretag calibrator and software can be used to accomplish the task. Many of the less expensive monitors can be profiled very well.
However, not every monitor on the market can be used. A monitor needs to have a brightness of at least 300, contrast of 700+, and control of each of the RGB colors. Do not get a monitor with over 2000 contrast. The software walks you through the settings on the monitor and sets the color density curve on the video card.
Monitor profiling is fairly straightforward. The profile made is directly related to the settings on the monitor of brightness, contrast, and color. Only one setting on the monitor can be used per calibration. There are some good choices of less expensive monitors that you can calibrate and will portray a very good spectrum. Go to monitors for our recommendations.
The monitor calibration controls the color and brightness of the white point of your chosen color temperature, such as D65 (daylight), and the black point. Then it forms a smooth curve between those points.
The choice of color temperature is extremely important. It relates directly to how the output image will be viewed. But here’s the rub! If you are printing for a gallery that views their prints via incandescent lighting (3400K), no monitor today can be calibrated to that low a color temperature. You will have to choose a point that a monitor can be calibrated to, such as 5000K (D50) and you should purchase viewing lights that match that temperature. Ideally, you should measure your lighting and set that temperature of the lighting during calibration.
Printing press viewing conditions have been D50 for years, but it’s advisable to check with the printer for his or her settings.
As you lower the color temperature on the monitor from D65 to D50, you also lower the monitor’s blue setting. Blue contributes greatly to contrast. Therefore, you need to choose a monitor with high brightness and contrast around 800.
Once the monitor is calibrated, you now have the ability to view the image as it will print. But will we be able to print the colors in our image?
Output Color Space
How does a digital printer know how to reproduce that image? Can the printing press accurately reproduce my page colors? Can the poster or sign reproduce the Pantone colors I have chosen?
The answer is that each device on its own has no intelligence. Ink, paper, and the printer are all dumb. A digital camera can offer you a raw color space or a designated one. There are hundreds of monitors and video cards that give you a basic image, but while the monitor and video card have preset color settings, they are not color accurate and not necessarily portraying the correct tonal value and shadow detail. You bring the intelligence to this process through color management.
So far, we’ve chosen an input profile and made a monitor profile. Now we have to make an output printing color profile. This is accomplished by printing a set of color patches that represent gradations of the color spectrum and then reading them in with a spectrophotometer. Color management software takes the difference between the color of the patches sent to be printed and the color that was printed and creates a profile that when used in printing or soft proofing corrects the color of the output to match the color of the input. I call this complimentary non linearities. However, if the output inks and media controlled by the printing software cannot reach the color of the input image, then the output will not match the input. So, it is important to choose a wide gamut rich ink set and media that can reflect color extremely well. This is where the discussion of what ink to use comes in, whether a standard ink set is good enough, or whether it is necessary to use multi-channel ink colors. This explanation is found in ink sets.
Output color profiles are made to be the printer’s color i.e. cyan, magenta, yellow, black, and any other color or colors such as green or red. That is where you have heard this is a CMYK profile. If you are printing through Photoshop with the Epson driver, you will need to make an RGB proofing profile that links the input image profile to the output profile set up by Epson. If you are going to use a full RIP that directly relates to the output color inks, then you will be making a CMYK or a multi-channel profile. This type of profile offers far greater control. When you purchase a RIP or color management software, you will learn the step-by-step procedure. Go to RIP Symphonic Evolution to see the controls offered.
Why do I need a RIP?
Each printer may have different characteristics due to the fact that the print heads are not made to matched standards. The atmospheric conditions of each location can affect the performance. Low altitude, high altitude, and variances in humidity are some factors. Each batch of print media can have coating differences.
Printer manufacturers do not support third-party materials or inks and do their best to prevent you from using them and being creative. Each of us have our favorite media and most of the time it is from a third-party company.
To think that you can adjust for all the differences by working Photoshop curves is foolish. While you might find a few media that you can work with the same profile, most of the time the differences are too great.
A third-party RIP allows you to to work with any combination you want. It gives you complete control and by choosing cost-effective media and ink, you can save a bundle—well beyond the cost of the RIP in a year.
What is the part a RIP plays in making a profile?
I cannot stress the importance of a good RIP. The RIP has many functions, including controlling how much ink is laid down. The RIP must be able to limit the amount of ink laid down to prevent excessive use, causing blistering, blotching, and blocked-up shadows. Each RIP handles this task a little differently. Ideally, you want to limit each color ink independently to its highest density on each media to obtain the widest overall gamut. This means that cyan might have to be limited by 15%, while magenta might be limited by 25% in order to reach its highest density before the densities flatten out.
After limiting the ink, you must linearize the amount of ink from 0 to 100%. This is basically like a stepped grayscale of each color.
How is a profile made?
After the RIP has been linearized, a chart of colors is printed out and, with the the use of a spectrophotometer, read into the color management software. The printed data is compared to the original data sent by the software and a map data file of the entire printable color spectrum of your media and ink is created. This map is called an ICC profile.
How do I control the black ink?
The new color management software has a feature that allows you to control black independently from the color channels. You can control the black to enter only in the shadows and vary the percentage of black from 0 to 100%. All this information of control can only be used in making CMYK or multi-channel profiles, not in RGB.
What must I know about black ink control?
Black ink is used to replace color in the shadows in order to reduce the total amount of ink used and increase shadow detail. It is also used to increase the density of 3/4 tones. Solid colors may not be deep enough without the addition of black ink. If too much black ink is used, it may overpower color, resulting in abnormal looking, over-darkened shadows.
Too much black ink used will decrease the color gamut. Too little black used can cause a flatter image.
How do I know how much black to use and how it should blend with color?
The answer relates to the dynamics of the media and ink, not to mention experience. These are some of the special topics that we teach in our seminars.
Where do I place the ICC color profile?
The profile may be used in either Photoshop or in the RIP. The conversion engine (software) contained in Photoshop and in the RIP applies that profile data to the image file in order to correct the file for printing.
It is sometimes thought that you can simply gray balance the ink and avoid making a profile. Please be aware the even if you can set curves to create a gray balance, it does not mean that all or any colors will print accurately.
For example, in order to produce a middle ton gray, more magenta ink is needed. In order to produce a middle-tone brown, more green ink is needed. The profile will map the colors to accomplish this result. However, this cannot be accomplished by simply using color correcting filters, because while you would be correcting one color, you would be adversely effecting another, or in this case, if you add green and then you add magenta, you have effectively cancelled each one with the other.
Similarly, if a media appears to have a yellowish white, the image will tend to print neutrals more yellow and light shades of blue will not print accurately. The profile will have the ink heads print more blue to compensate for the yellowish media.
A review of popular profiles
There are several RGB profiles that have been created to allow the image to capture all of the existing color. Adobe 1998, SRGB, ColorMatch and ProPhoto are some of the most popular. All images must live in a defined color space. What this means is that when you bring an image into a graphic program such as Photoshop or Illustrator, the program needs to define the image structure in order to portray that image correctly. The larger the color space, the more difficult it is to reproduce.
ProPhoto is the largest color space, while Adobe 1998 is the most popular for photography. It accentuates yellows and greens. For many years, ColorMatch offered a balanced color space used by reproduction houses.