Best ways to scan and remove dot pattern or texture from a printed photo
Removing Texture from a Photo
Many printed images have small patterns that are hard to see with the naked eye. Looking closely with a loop (or scanning and upscaling an image) reveals a texture that you don't necessarily want to replicate on a larger print. These patterns may have come from glue dots of a photo album, or simply the style of printing an analog photo that has been 'screened' onto the paper (think newspaper images). Sometimes, these are not noticeable on an individual photo, but much more of an issue for reprinting or blowing up an image for a poster or photo restoration. Here are a few strategies to get rid of that texture with the least amount of blurring possible when repairing an old photo.
Photo editing software: Blurring tools
Applying a smoothing or blurring filter will easily get rid of an overall texture, but used too much will also smooth all of your details. You might lose the sharpness and realism your photo has by blurring too liberally. Masks can help to selectively smooth over a certain area, or you can use what’s called a blurring brush to conversely only blur as you paint with your blur tool. This method gives a lot of room for personal subjectivity and customization, however, it can take a very long time.
Through the half-toning process -- when ink is passed through screens, and 'half the tone' is shown -- a dot pattern is created in the image. This is most commonly seen in comic books and images printed on newspapers. The purpose is to make an analog photo print properly and not too dense. Literally, the photo image is recreated by passing ink through a 'screen' and recreating only some of the image in ink.
Some scanners, like the Epson v600 Professional Series, have a checkbox for adjustments called "Descreening". If you check this box before scanning the image, the scanning software will look for recognizable patterns and remove them. This is a great convenience when it works, because you don’t have to manually find and edit these problem areas. But patterns are not always recognizable and the process will only allow for smaller images at lower than our recommended 300dpi (at least with the Epson).
FFT (Fast Fourier Transform) Software
Developers are coming out with new algorithms and software all the time. This particular method is another way to help suppress unwanted patterns that a computer can recognize on images. If you are into editing photos yourself and are familiar with Photoshop, customizing Photoshop with this process on your computer is possible with available plug-ins:
Or you can simply download a stand alone application like imageJ:
You will have to research how to use each type and version of software to understand how to manipulate the image into the result you are looking for. Here is a resource to help you should you want to brave the complicated waters of FFT.
Scanning at multiple angles
The “Subtract” tool uses Photoshop’s ability to determine differences in two photos and eliminate (or subtract) those differences. This is often used by photographers to remove tourists from pictures of a busy landmark, and can be very helpful in removing shadows caused by texturing.
You will notice texturing right away with images that have “bumps" from photo albums. Since scanners usually pass light going from one end of the scanner to the other, after scanning a textured photo, shadows all go the same direction in the pattern of your scanned image. Try doing another scan with the image placed at another angle and keep both scans. Line those digital images up in Photoshop and change the blending mode to "Subtract" to cancel out the dot pattern as much as possible automatically.
Bottom line: To properly scan a photo for the purpose of archiving, photo restoration, retouching, or recreating, you want to perform the best possible scan to minimize non-image elements present in the original photograph.
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