The guidelines below are for black-and-white halftones printing on Bookmobile's black-and-white printers: the Océ VarioPrint 6320. For our 4-color printing, please see our Print Settings Files for Color Interiors and Covers.
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Levels and Curves adjustments are similar in that they both adjust an image’s tone. Both Levels and Curves allow you to change the black and white end points of the tonal range in the image, which allows you to adjust the contrast of your image.
The difference between Levels and Curves is that Levels will make tonal adjustments throughout the entire tonal range when moving the sliders. Curves allows more precise adjustments with the ability to adjust specific tonal ranges—such as only affecting the Midtones, for example.
Notice that the image below on the left doesn’t take advantage of the full dynamic range, especially in the highlights side of the range. This can happen during a conversion or compression, but it can be corrected.
In the image on the right, we’ve moved the highlights slider down to 196. This stretches the histogram so that it takes full advantage of the entire dynamic range of colors instead of leaving out the highlights. Also, while holding down the option key (on a Mac), while sliding down the slider, you’ll be able to see when/which pixels will start to be effected. That will help show you when to stop—if you go too far you’ll start to clip pixels from the lightest area. This adjustment can also be made by a Curves adjustment as well.
Below is an example of a standard S curve tone adjustment using the Curves adjustment tool. S curve relates to the shape of the curve that is created by dragging a point in the highlights upwards and by dragging a point in the shadows downward.
A midtone point can be used to anchor the midtones if necessary. This adjustment can be used for boosting tonal contrast. The image below on the left is the original, and the image on the right shows the curve applied.
Any questions? Let me know!
We’d like to thank our Preflight Manager Paul’s dog, Lola, for participating in these guidelines. She’s a good girl!