Void Pantograph Creation

[Benk]

Hi everyone,

I am trying to create a void pantograph. I have experimented with numerous halftone screen frequency and angle combinations but still haven't found the magic formula. I am working on the basis of background 130lpi and the viod text at 65lpi. I have tried many variations of colour from 5% to 15%. The magic formula still eludes me.

Can anybody shed some light please.

All feedback will be much appreciated

Ben

 

[DCurry]

I've seen some where the VOID part is a different dot shape, or even just lines rather than dots. I used to make them long ago, but I can't remember the combination. I think I did the background at 175 or 200 and the VOID at 65.

 

[Stephen Marsh]

I'm with Dan. I used to do this around 25 years ago when I apprenticed in security printing and I can't recall the exact screen rulings or ratios between both elements. I am pretty sure that the main background was a regular halftone screen and that the void text was a line screen (or vice versa). The void text was next to invisible on the offset print, however if copied it became very apparent.

EDIT: This has come up a few times in the past, perhaps do a search.


Stephen Marsh

 

[mazengh]

i am interested in running a test on our speedmaster 52 but can't promise to run it very soon. I have to wait for a job where I have some white areas. Give me multiple screens to test along with our 200 lpi screening.

 

[gordo]

Typically pantographs use two screens that are the same tone in the final presswork. One screen is at a (coarse) frequency that can be copied, the other at a frequency that is at a higher frequency - one that is higher than the resolution of whatever might be used to copy the document.
The haltone screens don't have to be the same kind - i.e. AM (e.g. 100 lpi) can be used for the main art and FM (e.g. 20 micron) can be used for the "void" art.
The key is to match the tones in the presswork and to have the void part of the art at a higher frequency (lpi/micron size) than the main art and higher than the resolution of a copier or scanner's capability. The actual tone percentage is not the key issue other than if the tones are too light or dark both will fail to be reproduced and the "void" may not appear.

Best, gordo

 

[Mcat]

You will want to be careful of the LPI and structure you use to build the void panto. There are still live patents out there which if you create and sell will be infringing on. There are some which are prior art and free to the public like SR Big dot Little dot which is in the line screens you posted 133 lpi background and 65 lpi wordbut doesn't not work as well on the new type of copiers and another which is called ODT which the patent lapsed but has a special non geometric background pattern. There is also Induced moire which is also expired same line lpi background and word.