Back in the days of photo-offset typesetting, we used “photo blue” (non-photo-reproducible blue) felt-tip markers to mark up pasteups of pages for typesetting, knowing that the blue marks would not be “read” by the cameras.
Now, we don’t use cameras. We use photocopiers and digital scanners to make pages into images for reproduction.
The problem is that we often have to put marks on text as we read them. If we forget to first make a clean copy, then someone has to go through and white out all the marks before the pages can be copied.
What I want to know is whether anyone knows of any modern equivalent of photo blue markers whose markings will not be reproduced by photocopiers or scanners.
Bingo! I just did an experiment – I marked up a page using a non-repro blue marker, and purple, green, and yellow highlighters. The yellow highlights did not reproduce. All the other markings did reproduce.
There is a particular shade of blue that most photocopiers won’t reproduce - by design, I believe. I often use graph or quadrant paper with this shade of gridlines on it. In fact, I have here immediately at hand a pad of Staedtler “Layout Bond” which emphasizes on the cover its “Non-Photo Blue Grid.”
And as noted, blue highlighters generally don’t copy very well either. Other colors, such as orange, however may be rendered totally opaque. Testing the five usual highlighter colors on my copier I find that both yellow and blue do not reproduce except where the application density is quite high. Orange is nearly opaque; pink and green are somewhere in between.
The problem is that a color scanner isn’t a black and white photocopier or stat camera.
Scanners are designed and marketed on the basis of excellent color fidelity, so I’m not surprised they reproduce “non-repro” blue just fine.
And to think, I thought this was a plea for help with non-repro pens. I’ve never had much luck with them - press too hard, and they will be picked up, or if the ink blobs, you’ll see spots. For this reason, I’ve always stuck with the pencils.
Very good point. In my situation, the document is photocopied before it is scanned. So I just have to make sure that there are no marks on the version that goes from the photocopier to the scanner.
If the documents were scanned directly, I’d suggest a software solution; most image editing tools have a colour replacement feature, so you could mark up in any colour that wasn’t too close to anything that you wanted to keep and just remove it after scanning. Mono photocopying before scanning will thwart this though.