Targeting

Every printing system is going to look different from what you see on the screen. This is the nature of the beast. To eliminate these differences, you must modify the image before printing so that the print matches the screen. This is called targeting.

There are several ways to target for a specific printing device and medium. The most precise, complicated and expensive way is to use profiling software and color management. The least precise, simplest and cheapest way is to do it by eye. It is a less precise approach, but as you gain experience, you'll find that you can get closer and closer to "perfection".

Profiling Software

Though I have no experience with profiling software, I am familiar with the theory, and can summarize it for you. Basically, you print a test image, then scan it using either a calibrated scanner, or a color measurement device of some sort. Then the profiling software takes these measured color numbers and figures out how the image would need to be changed to get the "perfect" print. The result is a color profile that your color management system can use to modify your images before sending them to the printer for printing.

In theory, this should work great.

Profiling By Eye

I don't have a lot of money to blow on profiling software and color measurement devices, so I've devised my own profiling process that works surprisingly well. The premise is simple. Print an image you are familiar with, then compare the print to what you see on the screen. Adjust the screen image until it matches the print. Make a note of these adjustments, and figure out the exact opposite adjustments. Now use these opposite adjustments on the image and do another print. This print should be really close to the original screen image.

Comparing the Output to the Screen.
The trickiest part here is lighting the print. You should light the print in the same way it will be lit when displayed. Daylight is a good compromise if you can somehow swing it. Also, you're screen had better be working properly. Be sure it has warmed up, and use adobe gamma, or other tools to be sure you have a proper black point, and no serious color casts.

Adjust the Screen Image to Match
Each imaging application has different tools for adjusting color and tone. I'm most familiar with Photoshop, so I'll talk in terms of Photoshop's tools.

First you'll want to look at the overall brightness/darkness of the image. This is the easiest thing to adjust. Use the Levels dialog and adjust the gamma (middle input slider) until the image brightness matches. A black and white image would be easiest to work with.

Next, the color balance is a good thing to check. If the print appears yellow compared to the screen, go to the blue channel in the levels dialog and adjust the gamma to match. Too red or cyan, adjust the red gamma, etc.... Believe it or not, printing a black and white image can help a lot here.

Saturation (amount of color) is important to match up, and also fairly easy. It's best to do the saturation after you've adjusted brightness and color balance with a black and white image. Then the only thing remaining to check is the saturation, and this requires a color image. Print the color image using the opposite of the adjustments discovered so far. Go to Photoshop's Hue/Saturation dialog and adjust the saturation until the print and screen match.

Figure the Opposite Adjustments
Now that the screen and print match quite closely, you can figure out what changes need to be made before sending the image off for printing.

For gamma adjustments, you will take the reciprocal. For example, an overall gamma adjustment of 1.1 in the RGB channel means you need a gamma adjustment of 1/1.1 (.91) in the RGB channel before printing.

For saturation adjustments, simply negate the value. For example a saturation adjustment of -10 means you need a saturation adjustment of +10 before printing.

Once you've written a list of these opposite adjustments, you know what needs to be done to the image before sending it off to be printed on the specific printer being tested. In Photoshop you can create a macro that adds adjustment layers with all the needed changes for you. This makes it very simple to target for a particular printer or printing service in one click.

Conclusions

For me, this technique has worked surprisingly well. And as I pointed out, the better I get at seeing color, the better I am at matching screen and print. Consequently, the better my profiling becomes. The other nice thing is that you don't waste tons of prints doing tests. One black and white, and one color test print is usually sufficient.

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