Most of the time, if your file contains an image, you’ll want that image to be in bitmap mode for a nice clean bite into your paper. Otherwise your image will produce a halftone, which means your image will be made up of tiny dots on the surface of your plate.
If you zoom in on your image and it is made up of tiny grey and black pixels, it’s in grayscale. We want your images all in black pixels.

You can correct this by:

• Opening your image in Photoshop and selecting Image > Mode > Grayscale.
• Select Yes if a window asks about discarding color.
• Then Select Image > Mode > Bitmap. A window will pop up looking for info – use a resolution of 600-1200 dpi and an output method of 50% threshold.
• Save your files as a tif (with LZW Compression) and send us the tif. Or insert the Tif into your Illustrator or InDesign file.

Images in higher resolution (600-1200 dpi) will give better, finer results than images in lower resolutions (72-300 dpi). If your images lose a lot of detail, you can either re-scan or adjust your levels of black. A quick explanation about the 50% threshold method. A grayscale image is made up of pixels from 1 – 100% black. When you select 50% threshold, you are telling the computer to change all pixels less than 50% black to be white and all pixels greater than 50% black to be black. So sometimes adjusting the levels of gray pixels under 50% to a little darker and over the 50% mark will keep more details in your image. We suggest experimenting with the following: Image Adjustments > Levels or Image Adjustments > Brightness and Contrast. This may give you more pleasing results in your final bitmap tif.

The ideal LPI depends on your paper and presswork, but most printers printing on uncoated paper use a 100 LPI. It’s a good balance of fine screen and easy printing. The higher the line screen, the more difficult it will be to print, because the high line-screen plate plugs up with ink in the shadows and looks murky over-all. Some printers prefer playing it safe and order 85 or 65 LPI. Using a lower LPI does make the dots coarser and more obvious. The finest line screen that we usually process is 133 LPI, although we would even question the use of 133 LPI, except on coated or hard papers.

If you’d like a halftone for your image, don’t adjust or apply an LPI in your file. Just tell us what LPI you’d like us to use, and we’ll take care of the rest.

If you tell us the paper, the type of press you’re using, and what you hope to accomplish with your halftone, we would be happy to recommend a line screen for you!

The amount of dots in an inch of a halftone is determined by the LPI, also known as line screen. The higher the LPI, the more dots there are per inch. A higher LPI means the dots are smaller and less noticeable. Letterpress printers typically use between 85-133 LPI for their halftones. We find that 100 LPI is a good choice for all plate types and is the default we apply if you don’t specify.

The technical definition: a halftone is a matrix of different size dots which allow printers to simulate tonal variation when printing with a single ink on press. What this means: a halftone allows you, using one color ink, to approximate various shades of color. Take a magnifying glass and look at a black and white photo printed in your local newspaper. You’ll notice the image is actually made up of different size dots. The smaller the dot, the lighter the color in the halftone. A grayscale is made up of pixels that are in varying shades of black so the tones are represented by the different shades. Once a file has a line screen applied, the grayscale is now a halftone.