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I have a number of old letters written by my mother in a military hospital in France, where she was a masseuse, in 1918. Most of these were written on both sides, with an ink-pen, on cheap paper, so that the writing shows through from the other side. I feel that it ought to be possible to combine a scan of the front with a mirrored negative scan of the back, so that the latter cancels out the ink that has bled through the paper, but I cannot work out how to do this.
If I were doing it in a dark room, I would take a negative of the original, and make a positive transparency of the reverse, turn it over, and bind the two together, then make a print. The white part of the reverse would be transparent, so that he would not affect the print of the front, but the dark parts would match the light parts of the negative of the front, where the ink had shown through from the back.
The electronic equivalent would be to scan both sides, flip the scan of the reverse left to right, invert to convert to a negative, darken so that all the light part became black, then add the two. The addition process would simply add the intensity of each colour at every point on the screen, so that white plus black stayed white, and grey plus grey became white. However I cannot find any process in Photoshop which does the equivalent of adding the two layers. I tried increasing the contrast of the negative layer, selecting the black, and deleting it, but this gave coloured fringes which considerably reduced the readability.
I also tried superimposing a positive of the reverse on the negative of the front, then selecting in the deleting the white parts of the reverse. This gave somewhat better results, but revealed that the process of selecting and deleting the back ground caused the width of the remaining lines to shrink, so that the bled through lines were wider than lines which were supposed to be cancelling them out.
When you fill a selection, you can give the fill colour any desired transparency, but I cannot find any equivalent effect for adding, rather than superimposing, layers.
I rather doubt if this process would be useful even if I could find out how to do it, but does anyone know how to achieve the digital equivalent of superimposing two negatives, or making multiple exposures?
James McNangle
If I were doing it in a dark room, I would take a negative of the original, and make a positive transparency of the reverse, turn it over, and bind the two together, then make a print. The white part of the reverse would be transparent, so that he would not affect the print of the front, but the dark parts would match the light parts of the negative of the front, where the ink had shown through from the back.
The electronic equivalent would be to scan both sides, flip the scan of the reverse left to right, invert to convert to a negative, darken so that all the light part became black, then add the two. The addition process would simply add the intensity of each colour at every point on the screen, so that white plus black stayed white, and grey plus grey became white. However I cannot find any process in Photoshop which does the equivalent of adding the two layers. I tried increasing the contrast of the negative layer, selecting the black, and deleting it, but this gave coloured fringes which considerably reduced the readability.
I also tried superimposing a positive of the reverse on the negative of the front, then selecting in the deleting the white parts of the reverse. This gave somewhat better results, but revealed that the process of selecting and deleting the back ground caused the width of the remaining lines to shrink, so that the bled through lines were wider than lines which were supposed to be cancelling them out.
When you fill a selection, you can give the fill colour any desired transparency, but I cannot find any equivalent effect for adding, rather than superimposing, layers.
I rather doubt if this process would be useful even if I could find out how to do it, but does anyone know how to achieve the digital equivalent of superimposing two negatives, or making multiple exposures?
James McNangle
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