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Making the Most of Pin Registration

(May 2003) posted on Tue Jun 03, 2003

Discover how to refine each step of the prepress workflow so you can realize the benefits of pin registration.


By Mark A. Coudray

Position your image according to any layout grid you use. Make sure to look at the positioning under at least 10x magnification. When you position the film, tape the top of the film nearest the register pins first. Then, using your dowel, carefully squeeze the air out from under the positive. Tape the tail, and be careful to apply slight downward tension onto the tape and positive, away from the pins. Doing so helps to avoid any film buckle from shifting during exposure.

 

Apply a second carrier sheet over the first. Repeat the dowel process. Very carefully position the next film separation over the initial positive. Make sure to use magnification to assure accuracy of placement--do not trust your naked eye! Tape the head first, nearest the register pins. Dowel out the air and check the tail-register marks under magnification. Make whatever small adjustments are necessary for perfect registration and tape the film down to the base.

 

When you complete this step, remove the second carrier from the pins and replace it with a new one. Repeat the process until all colors register with the base positive.

 

When you are done, stack all of the positives up on the pins and check for collective alignment. Inspect the alignment under magnification and be sure to look exactly straight down. If you position yourself at any angle to the loupe, you introduce a <I>parallax error</I>, which prevents precise registration.

 

Screen exposure

 

The next step is exposure. Many bad things can happen during the process because the amount of force exerted on the screen and positive is huge, and the force of vacuum drawdown moves anything if given the slightest chance. But you can minimize the threat of registration error at this stage.

 

First, make sure that your screens are absolutely flat. The frame must be free of wobble and rack. If you lay the screen on the exposure glass and there is any movement at the corners when you press on them, your image is guaranteed to be out of register.

 


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