Photoshop training is an important piece of the prepress puzzle. If you’ve been plunked down in front of your computer and scanner and you haven’t been given adequate training in Photoshop, you’ve been set up to learn some expensive lessons. There’s always a reason why photos come out like mud off the press. And that reason can often be found in the numbers.
Muddy photos are one of the most common problems with inexperienced Photoshop users. Knowing how to set up your images so they perform well on press is a crucial skill. Whether you learn this in a classroom, from a book, website, or interactive DVD, when you learn Photoshop from a pro, you’re ahead of the game.
Want to stay out of the (Photoshop) mud? Read on …
Highlights and Shadows – Follow the Numbers
Looking at the numbers when scanning is the final assurance of good quality. Even with a calibrated monitor and scanner, you will need to establish proper numbers in key areas of the scan. This is especially important in the highlight and shadow areas, since most color monitors fall short when showing good highlight and shadow detail.
Typical white highlight values should be about equal amounts of yellow and magenta with a little more cyan. For example; 3-5C, 2-3M, 2-3Y. Why are the numbers unbalanced and not equal, you ask? Its all in the inks. As a rule, all process color inks are contaminated in some fashion.
Cyan, magenta, and yellow inks printed in equal percentages will reflect more red light. This results in a reddish color cast. To compensate, youll need to unbalance the inks by increasing the cyan amount. A average midtone gray will be around 50C, 42M, 42Y. This same relative balance applies to the highlight and shadow, as well.
The shadow values will vary depending on the type of paper that the image will print on. Newsprint values will normally be the lightest, with percentages around 70C, 65M, 65Y, and 70-80K. Commercial work should have percentages around 90C, 85M, 85Y, and 85-95K. Looking for these key areas of white, black, and gray, and then establishing reliable numbers will eliminate some of the guesswork involved in scanning.
Once youve established those numbers, youll want to analyze contrast. With the balance of the color separation in order, you can examine the overall brightness of the image. By the way, if there is not a white, black, or gray point to examine, simply skip that step in the process. The best way to establish good contrast is to ask yourself a few key questions. Contrast is best defined as the separation between light and dark areas.
- Can the whites be whiter without losing much detail? If the answer is yes, you can use one of many controls either on the scanner or in Photoshop to reduce the tone values in the white areas.
- Can the shadow area be darker without plugging up the detail? In some cases, by making the shadows dark, the whites appear whiter, resulting in more contrast.
- Use caution when adjusting contrast with slider- type controls. These controls
are okay, but you need to watch the numbers because the white areas can easily be reduced to nothing and the black areas may go solid, resulting in an unwanted appearance.
This section on highlights, shadow, and contrast originally appeared in The Photoshop Plug-Ins Book.