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Photo Retouching "Improving" photos, post-production, correction, etc.

Reduce "Scanner Streaks"

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  #11  
Old 12-02-2003, 03:38 PM
darkmke darkmke is offline
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I figured that I would post something just to answer some of the questions raised about the de-interlace filter. Some quick background: I work as a video editor and deal with de-interlacing all the time. I also do photography as hobby, I was looking for tips and tricks because I have some old photos that need retouching and stumbled across this. Anyway on to the reason for the post.

In video all that maters are pixels (there is no DPI or variation in size) An image can never be more pixels than there are on the Monitor. Without getting into too much detail, a video frame is made up of 2 images. Each image is called a field and is the full horizontal resolution but only half vertical resolution of an image. The final frame consists of a combination of the two fields. The horizontal lines in the two fields are combined every other line, this is called interlacing. The fields are labled because of their position in the image creating an upper and lower (odd and even) field. The De- interlace filter removes every other horizontal line (removing 1 field) clearing up the image. The interpolation fills in the missing lines to retain the orignal size of the image. The de-interlace worked in the sample case because the lines were 1 pixel and were removed by running the filter, this is also why the filter only works horizontally. No matter the size of the image the de-interlace will always remove every other line of the image, making it hit or miss when your trying to remove lines. I hope this helps the understanding of what is going on and possibly when it will help with your images.

Mike
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  #12  
Old 12-08-2003, 01:06 PM
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Flora Flora is offline
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Hi Mike!

Welcome to RP ....

Thank you very much for your explanation ... I didn't really have a clue on how the De-Interlace Filter worked .... I was experimenting, trying to reduce those much 'hated' lines ..... and now, reading your post, I know I've just been lucky it worked....
To tell the truth, after that experiment, I didn't go near the De-Interlace Filter again... but now, after reading your very helpful explanation, I feel curious and might try it again .... Thank you!

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