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It has been over 30 years since I did these, I have probably forgotten a lot...
A sample image link follows. Flatten the linked sample and convert to bitmap mode at 2400ppi using 50% threshold method.
Test print at the highest resolution available at 100% magnification/same size.
This uses a background "stipple" of 45° round dots at 120 lpi frequency.
The text is using a "line" pattern at 45° at 120 lpi frequency.
It will take a lot of experimentation, trial and error. It will depend on your out
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I have created an action to help those that are having problems creating the pantograph image. Ideally this would be created in Workflow/RIP software and not in Photoshop.
One can adjust the size and resolution of the background image, however, I'd recommend working at 1200ppi or 2400ppi. 600ppi may be too low, however it would depend on the output resolution.
One can also adjust the text content, size and positioning.
You can download the action from my dropbox here:
https://www.dropbox.com/s/khhcccgl7ipgxi3/Void%20Pantograph%20Creator.atn?dl=0
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Stephen-
The file you provided is INCREDIBLE! I printed the file out on our color laser printer (Phaser 7800) as-is and it didn't work very well (I didn't read/do what you instructed) as the grey box and VOID both printed although the text was just slightly visible against the background. I put the print on the copier and the text did pop out a little more. So it KIND OF worked. I then studied the file and thought maybe if I connected the end points of the lines to the dots with the brush tool it would prevent the text from being visible at all on the original, but even with it set to 100% hard edge there was some blur to the brush. So I converted it to bitmap 1200 dpi / 50% threashold and then connected the ends of the lines to the dots adjacent to them (no brush blur). I printed it out and all I got was a grey box, couldn't see anything else. Put it on the copier....BAM!!! No grey box, just "VOID" appearing on the paper!!! WOW!!! JUST WOW! Thank you so much!
Grateful for your help friend!
I provided full instructions and a layered file earlier in the topic thread. I’d suggest that you read my post again.
I used Photoshop bitmap mode halftone screen conversions as I no longer have easy access to an image setter RIP and or Workflow software that can apply different screening at the object level. This uses background "stipple" of 45° round dots at 120 lpi frequency and the VOID text is using a "line" pattern at 45° at 120 lpi frequency. I believe that the original tint value was 15% for both background and text.
For offset printed work this would be best performed using workflow/RIP software at the highest possible resolution 2400 ppi or higher as supported by the platesetter.
Back in the early 1990’s when I worked for a security and forms printing company, I had to make two separate sequential imagesetter exposures to the same piece of film in order to burn different screen patterns on the same separation. I may only have performed this operation a handful of times back in the day, it was not very common. Perhaps we had to burn positives, then dupe the composite screened film into a negative, before plates were exposed, I really can't recall with any accuracy.
Many modern workflows offer the ability to tag different objects with separate screening data that will be applied at the object level, overriding the screening used for the rest of the plate.
As press time is expensive, I would see if you can gang up multiple samples on the same plate. Perhaps positioning the same test patterns in random spots over the width and depth of the sheet to ensure that printing was consistent.
Look into using the same tint percentage value for the text and background and try different tint strengths. I’d stick with a 45-degree angle for the background tint, but you could try different line angles (0° or 90°) or perhaps use dots with differing LPI values or angles rather than a line screen etc.
This may not be as easy as with digital printing. I’m going from very fuzzy old memories that predate CTP and things have likely changed with modern software and hardware. Good luck!
Your PDF has some issues.
As previously mentioned, the resolution needs to be very high for bitmap mode halftones, ideally 1200 ppi or greater at 1:1 print size. The final image mode should be bitmap, not greyscale or RGB etc.
Your sample is approx 44 x 23 mm in size.
This would create an image around 2100 x 1050 px in size @ 1200 ppi for an approx. print size at 1:1 scale of 44 x 23 mm metric size.
It is critical that no resampling or colour mode changes are made from the final 1:1 sized bitmap mode image and that page layout software does not change the Photoshop 1:1 size.
You would need to test the lowest PPI value that produces acceptable results for the output size, device resolution and printing process.
You could also edit the action to make the backgound use lines rather than dots and the text to use dots rather than lines. You could als experiment to change the angle of the lines from 45 degrees to horizontal or vertical (I'd keep the dots at 45 degree angle though).
PDF sample attached of how this should look. Compare to your file and you should see where you went wrong. Saved with no downsampling and lossless ZIP compression from the final bitmap mode image. This was created at 1200 ppi resolution, you may need 2400 ppi or greater resolution to optimally resolve the dot and line screens.
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