Digital format for exactly life-size reproduction

[BetterSense]

I'm a real noob at digital workflow so please help me out.

I am making photograms by printing real-world objects directly to lithographic film. The resulting photogram can be used as a stencil in manufacturing, and retained as a reference for QC.

I would like to digitize these photograms in such a way that dimensionality is maintained, and I can print copies onto clear sheets. What is an acceptable digital format that will facilitate this kind of life-size printing? PDF? Postscript?

It may be simple to just plop the litho film onto my office's copier/scanner and 'scan as pdf'. Then, if I print the resulting pdf files back to clear film, I assume that the print will be dimensional, to the tolerances of the scanner/copier. Is this a valid assumption? What 'gotchas' might there be? For example, if someone tries to print them onto A4-size clear sheets instead of 8.5x11, I don't want the dimensions to change.

I might wish to do some image processing for contrast, inversion, etc. which might require me to convert the pdf to some more standard image format--I don't know if pdf files can be natively manipulated. In that case, I'm not sure how I can maintain dimensionality such that I can convert back to PDF and maintain scaling. If you were faced with this task, what workflow would you use? Any advice is appreciated.

[jp]

Tiff maintains dimensions. pdf/ps does too, but it's not easy to edit a pdf/ps scan. Some viewing/printing software autmatically sizes pdfs or images to fit page, but that's easy enough to check.

[rdenney]

For scientific work, include a good ruler in the scan. If that lacks sufficient precision, then you have to scan at a known resolution and the avoid any subsequent resampling. You should probably also test that the reported resolution of the scanner is sufficiently accurate. Then, you can measure things by counting pixels.

I would then use software that allows you to scale images precisely, and then include a scale bar, or the important dimensions, or both--just the way drafters used to do.

Many CAD programs can precisely scale bitmaps. This feature is used for making CAD design drawings on top of digitized aerial photos.

If you simply want a photogram that is the same size as the original for visual comparisons, set your scanner software to encode the file with a resolution the same as the scan resolution. You'll see something about scaling--pick the one that looks like "same as original". The encoded resolution is just a number. You can change it in Photoshop to the correct value after the fact. Just don't check the resampling box.

I would import the graphic into a page layout program at the correct size, and then make a PDF. Even Word would work for this. I've used Corel Draw for years for this sort of thing, but Adobe Pagemaker (or current equivalent) would also make this easy.

For even less precision, I have scanned receipts using my iPhone and maintained their approximate original size by laying a standard letter-sized sheet of paper behind the receipt. I then scale that to a full page when making the PDF.

Step one is to understand your precision requirements.

Rick "who does this sort of thing a lot" Denney

[BetterSense]

The photographs form stencils that are used in manufacturing QC to verify position of laser-cut text. It works really well. I can include images of rulers, but I still don't trust the end-users to respond correctly if they have to resize or something. I'm looking for about 200microns or .010" of precision.

Duping litho film sure is easy, accurate, and simple. I was hoping there was a digital equivalent, that my end-users can't mess up. I guess there is faxing, but you can't fax onto clear film, plus I'm not sure how good the tolerances are on faxes either. Maybe I should just budget for overnight snail-mail.

[Jim Andrada]

Current version of PageMaker is InDesign. I liked PageMaker better - used it for 20 years or so - but InDesign is a good package. Biggest loss from PageMaker was the concept that the space around the document was like the top of your desk and you could put text blocks or graphics or combinations on the desktop and flip pages and decide onto which page to drag and drop the snippets.

[jp]

Fax is 98 dpi in rough res; slightly under your precision requirements in a perfect world. However, most fax machines that feed the scans with a round platen have some slippage and don't scan perfectly uniform.

You can print laser prints onto mylar film, which is cheaper than mailing. I'd just print over a VPN to a remote laser printer.