In our example you might have noticed we used a very high resolution. In fact, the small 2 inch pattern we made was about 4 megs. A full comic page done at a similar resolution could be as large as 70 megs! There's a specific reason for this: a high resolution is needed to prevent a moire pattern.
Pixels are square. Dots aren't. Since Photoshop images are comprised of large numbers of square pixels, to render a small dot and make it reasonably round requires a fair number of pixels. Let's zoom in very closely to our Zip pattern to illustrate this:
In our example, the halftone pattern is rendered at 1000 DPI. With this number of pixels, Photoshop can achieve a convincingly round dot.
This image is the same halftone pattern but rendered at only 300 DPI. Notice how some of the dots appear malformed? Photoshop does it's best approximate a round dot, but with only 1/3 of the pixels to do this with the result just isn't very spherical. These alternately shaped dots can form their own undulating pattern in what's supposed to be an even tone. This is refered to as a moire pattern and it's pretty undesirable. Moire patterns are pretty common when two ordered fields are overlapped. The interaction between the two frequencies creates a totally new pattern. The frequency of this distortion is often refered to as the "Beat Frequency". pattern isn't too sharp.
For the purpose of generating Zip, I'd suggest a minimum of 600 DPI. 600 DPI works well for for larger Zip dots, generally 65 LPI or higher. 1200 DPI is ideal, and should be able to adequately handle smaller dots. Common ranges for LPI are usually between 45 and 150, with 150 being almost a fine, continous tone. Quite a bit of commerically available Zip is between 45 and 75 LPI.
In addition to being able to create standard halftones, Photoshop also allows you to create custom ones. This is a powerful feature that opens up a wealth of possibilities for toning.
Any pattern can be turned into a halftone. Start with any grayscale design on a square canvas. You can define custom patterns in Photoshop by selecting all and then [edit>define pattern...]. Small, seamless images tend to make the best patterns, but feel free to experiment. I'd recommend a decent range of grays as well, since Photoshop will have a much easier time making a smoother transition between light and dark if the source
Once you've defined your pattern, simply mode change to bitmap. However, make sure the Method is set to "Custom Pattern" and that you select the pattern in the pull-down pattern menu.
In my case, a simple black to white grad converted to a halftone with a generated this image:
The range of possible effects is quite varied, but the technique requires a lot of experimentation to produce usable results. However, it's time well spent since there's no other easy way to achieve such original patterns.
Photoshop has made the tedious chore of lettering much easier. Individual artists no longer have to train themselves in the discipline of lettering, or the expense of sending their work out to be professionally lettered.
As lettering is a faily basic function in Photoshop so there's not a whole lot to cover in terms of technique. A couple of points to keep in mind, however:
Lettering is generated on its own Text Layer, which means it can easily be redited. Be sure to save a .PSD version of the file in case of typos or dialogue changes. Text layers are indicated in the Layers Palette with a "T" on the preview icon. If you wish to edit the text as a graphic, you can rasterize it [layer>rasterize>type]. This can be important if you want to merge it with a balloon.
Since you're using fairly extreme resolutions designed for printing, make sure to turn OFF anti-aliasing on your letters. If the anti-aliasing is on, the gray in the letters will halftone, possibly making the lettering fuzzy. The anti-aliasing controls are located in the text options along the top of the screen.
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