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I have an old scanned book, which is of low scan quality. But for normal text pages, I can use PhotoShop to enhance it and this is an enhanced page.

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As you can see, it's basically readable. It could be further enhanced, but I'm not a PhotoShop expert and don't know how to do it. Some other pages are hard to enhance as they have a dark background in the top part of the page. Below are some examples.

enter image description here enter image description here enter image description here

How can I enhance them using PhotoShop so that they have a similar readability as the first image? Thanks.

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  • What have you tried? here is that failing?
    – Scott
    Oct 9, 2021 at 17:31
  • I tried to select the upper part and only process it. I tried several tools, like curve, white balance etc., but the result is not good as it basically splitted the page into 2 parts and they look very different after the processing. Oct 9, 2021 at 17:35
  • Can you rescan them in colour? Sometimes it's easier to remove a background if there is colour information in the image. Once you remove the colour, there's much less data and so getting a separation is much harder.
    – Billy Kerr
    Oct 10, 2021 at 15:03

2 Answers 2

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Something for the dark top areas of your pages:

Start by applying filter smart blur. It doesn't actually make your text more clear, but reduces the graininess of the unwanted noise by combining the particles. Play with the settings:

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As said, the smart blur step can be skipped, but there will be more fine grain in the end.

Duplicate the layer. Apply heavy Gaussian Blur to your top layer to fade text details:

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Invert the top layer (Image > Adjustments > Invert) and change its blending mode to Linear Dodge or Add:

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Insert a curves adjustment layer and lift the contrast with it.

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NOTE: The curve should be as mild as possible; vertical tresholding doesn't work, it makes the letters much rougher.

Approximately the same can be got a little faster with high pass filtering. Start by smoothing fine grains with Smart Blur as in the first receipe. Then fade large uniform dark areas by applying High Pass filter:

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Restore the contrast with curves. Again: vertical tresholding will not work, the curve must be as mild as possible.

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A mathematician might be able to prove that the methods are same in math. A valid proof needs underhood qualitative knowledge of Photoshop's functions. Adobe has kept those details well hidden.

NOT ASKED: If this was my job I would recreate the pages from scratch for ex. in Adobe Indesign, only signatures must be copied.

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I tried playing with this - Photoshop may not be the most efficient. But if resetting the page isn't an option, you can create a duplicate layer, change blend mode to screen, and then also apply Brightness/Contrast adjustment. Use masks to save the areas to remain as original. I also found it an either/or situation - either a second layer with just Brightness/Contrast and masking, or a second layer with blend mode set to screen and again use masking:

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