Cleaning Up Halftone Images


Today’s Question: I am recovering old photos from family history. I have discovered a good one, but it is a newspaper clipping. Therefore, it is made up from dots, like a Roy Lichtenstein painting. It is a great image, remarkably sharp and worth working on. Can you give guidance on how to bring this back to a normal photo eliminating the dots in Photoshop?

Tim’s Quick Answer: Photos printed in a newspaper are produced with a halftone printing process, which creates a pattern of circles in the image that can be problematic. You can help minimize this halftone pattern by applying a blur to the image and then sharpening the image. Image cleanup techniques can then help remove remaining artifacts.

More Detail: The first step in cleaning up the halftone pattern in an image is to blur the image to blend the halftone dot pattern. In Photoshop you can use the Unsharp Mask filter for this purpose. Choose Filter > Blur > Gaussian Blur from the menu. You will likely need to use a relatively high value for Radius, though this will depend on the size of the halftone pattern. Set the value for Radius just high enough to blend the halftone dot pattern in the image.

You can then sharpen the blurred image to enhance edge contrast. Choose Filter > Sharpen > Unsharp Mask. You’ll need to use a relatively high setting for Radius in most cases, compared to what you would normally use when sharpening a photographic image. Depending on the resolution of the image you’ll probably need a Radius setting of at least 5 and possibly higher. Adjust the value for Amount as needed to achieve improved edge contrast. You can also increase the value for Threshold if needed to prevent relatively smooth areas from being sharpened.

The key with this technique is to carefully balance the blurring and the sharpening. In some cases you’ll need to get very aggressive with both the blurring and the sharpening to get a good result. I recommend testing the process multiple times on the same image to get a sense of what is possible in terms of balancing the blurring and sharpening.

Once you’ve blurred and sharpened the image you can use normal cleanup techniques to deal with any remaining artifacts from the halftone printing. You may find the Dust & Scratches filter helpful for cleaning up a large number of small blemishes, which can be found on the Filter > Noise menu.