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Thread: best settings in IrfanView for viewing faint handwriting

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    Default best settings in IrfanView for viewing faint handwriting

    I'm not sure where to post this question, but I need to know the best settings to use in IrfanView for viewing a TIF file of a scan of an old mid-1860s era handwritten letter. The writing is very faint. I have scanned images at 2400 dpi resolution.

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    Default sample file

    Here is a small sample file
    Attached Images Attached Images

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    Moderator Enterprise User Bhikkhu Pesala's Avatar
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    That's pretty much unusable. Have you tried scanning in colour?

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    Quote Originally Posted by Bhikkhu Pesala View Post
    That's pretty much unusable. Have you tried scanning in colour?
    No, I have access only to the scanned images, not the original letter.

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    Even with a more sophisticated graphics program if the information is not there in the original image file you have there is no way to enhance it now. There may be high end specialist forensic software which could interpolate, basically 'guessing' some of the the missing information but from what you have available I think even that would be unlikely to provide much improvement.

    The original document is what is needed and if very faded even that may have to have scanned by specialists to make the information readable.

    In the film based still photography days a document of that sort would be photographed in ultra-violet and/or infra-red light using specialist filters and film materials to enhance the contrast and bring out the faded or hidden detail.

    The digital equivalent is much easier as sensors are general sensitive to both UV and IR and you can filter out the visible light fairly easily. But it is still a specialist area and you'd need a strong light source in both cases and a good document copying rig. I doubt very much that any normal scanner would or could be adapted to do the job directly.
    Last edited by BadRobot2018; 05.05.2019 at 09:54 PM.

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    Power User j7n's Avatar
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    Next time try to scan at maximum color depth, but less dpi, and don't use levels/tone enhancement in the scanning software. You can always reduce the bit depth later, after applying a contrast adjustment. The scanner usually bases its automatic adjustments on a reduced resolution quick "prescan" image which can miss some details.

    Resolution is more important when scanning images with fine patterns such as money or printed halftones, but even then going above 600 dpi gives minimal improvement, and the scanner's optical resolution becomes a limit (around ~1000). For natural images color depth is more important, even originally black and white images intended for screen viewing or processing should be in greyscale.

    For best results scan in 48-bit and process the image in Photoshop or other program capable of this precision. You might want to keep one of the color channels for conversion to greyscale, instead of standard mixing. For example, if the paper has brown stains, they might be less visible in the red channel.

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    You usually do not need specialists and specialist filters. With Irfanview you can manually set a fine threshold for an image scanned in grayscale if you want to convert faint handwriting to black and white, but if you ask to scan directly in black and white then even the best of scanners are usually not capable of correctly setting the threshold automatically.

    In Irfanview Open the image and use Image > Color corrections (Shift+G). Normally I start by setting Contrast to about 70, then increase Brightness by dragging the handle right until the image becomes all white. Reduce brightness very slowly until the faint writing is just visible again. When very close to the threshold I usually change from dragging the handle to typing the value directly into the box which lets you change the value by 1 at a time. Edit the value and press one of the navigation arrow keys to enter it.
    When the writing is just visible press Enter to close Color corrections. Then click Decrease Color depth from the Image menu and choose 2 colors (black/white) to see the result. I find that turning on the Floyd-Steinberg dithering function is helpful.

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    The problem is he doesn't have the original document so a lot of our advice is moot anyway.

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    Power User j7n's Avatar
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    He might work with another document again. Or another user might read and be tempted to buy special unnecessary software, when it is a matter of tweaking the parameters of the capture. I've seen several times before people choosing 1bpp color for text documents, possibly because in everyday language we call single component photos/movies "black and white", and today most experience of graphics is through video screens instead of a printer, where 1bpp doesn't work.

  10. #10

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    I certainly was not suggesting anyone buy special unnecessary software or even hardware for a job like this. My comments came out of my experience with using film for that sort of document copying task. I've no doubt that even with consumer level tools there are now far easier methods of enhancing such a faded document during a scan so that it is produces a more readable image file.

    However the use of both IR and UV in old document copying is still very relevant:-

    https://siarchives.si.edu/what-we-do...s-more-legible

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