Reduce "Scanner Streaks"

[Flora]

You might have already used it, but I discovered it while trying to find a way for reducing 'Scanner Streaks' ...

I'm talking about the De-Interlace Filter.

I tried it on several pictures and the results I got, even though far from perfect, were very encouraging...

For the following example, I used the picture submitted for Restoration Challenge #38 :

1) Duplicate the Background Layer.

2) Since the De-Interlace Filter seems to be working on horizontal lines only, if the streaks in your picture are vertical, Rotate the image by 90° (either way: CW or CCW)

3) Filter->Video->De-Interlace:

Eliminate -> Odd Fields
Create New Fields by-> Interpolation

4) Rotate your image back ...

5) Change the Layer's Blending to Lighten, press "V" (Move Tool) and use the Arrow Keys to nudge your Layer until the lines have nearly disappeared.

6) Add a Layer Mask ->Hide All and using the Eraser Tool, selectively uncover the corrections.

P.S. In the example, I only worked on reducing the streaks and beside a Curves Adjustment and a light Sharpening ... No other correction has been done ...

[jeaniesa]

Flora,

This seems like a really neat tip, but when I try the de-interlace filter, I don't see that it actually does anything. What am I missing? I can still change the layer blending mode to lighten and move it and see results - but I don't see any difference before/after running the de-interlace filter. Should I?

Thanks,
Jeanie

[Flora]

Jeanie,

the difference I saw trying both methods, with and without De-Interlace, was in the smoothness .... but, if you don't see any, it might be my monitor or my eyes....

[jeaniesa]

After playing around with it a little more, I discovered that if I reduced the size of the picture (so that the streaks were smaller), I did notice the de-interlace filter smoothing things out a bit. But, on larger pictures, it doesn't seem to make that much of a difference. A very slight motion blue in a direction perpendicular to the streaks seems to have a similar effect though - and can be adjusted based on the size of the image.

Thanks again Flora!

Jeanie

[Flora]

...In fact I've tried it only on small size pictures ..... I'll just have to 'experiment' with larger sizes .....

One question ....

..A very slight motion blue in a direction perpendicular to the streaks seems to have a similar effect though - and can be adjusted based on the size of the image...

... you really got me here ... ...What is it... and how do you do it?

Thanks ....

[CJ Swartz]

Flora -- I'm betting that the "motion blue" Jeanie mentioned will turn out to be "motion blur" (just one little letter ) - like what you did on the Moire Challenge a few months ago.

Flora, thanks for always looking for new strategies -- I thnk I used the de-interlace filter once to make TV lines, but I'm not sure. I didn't notice any difference myself when trying your method vs just moving the layers, but my vision is not very good.
I decided to see some of what it would do on lines, and made an image to show the effects of the different settings. I'm not sure what to make of the results, but there is definitely a difference.

[jeaniesa]

Originally posted by CJ Swartz
Flora -- I'm betting that the "motion blue" Jeanie mentioned will turn out to be "motion blur" (just one little letter ) - like what you did on the Moire Challenge a few months ago.

Thank you for catching my typo CJ! I was about to go into a long description about motion blur - didn't even realize I had a typo and that was the cause of the confusion!

Interesting test results CJ. Now if we can only figure out what it means!

Jeanie

[Flora]

Hi CJ, Jeanie,

Thank you very much for your reply

..I'm betting that the "motion blue" Jeanie mentioned will turn out to be "motion blur" ....

...how silly of me not to realize it .... ... It's not only my eyes .... it's my brain too ...

CJ,

thank you so much for having taken the time to dig deeper into the De-Interlace Filter ..... After having tried it on a bigger sized picture, I couldn't see the difference either .... so back to 'experimenting' ....

..So...if possible for me, I'll just delete this useless 'tip' as not to waste any precious space at RP ....

Thanks again to both of you...

[Stephen M]

A video de-interlace filter probably will not work well on images which are not characteristic of a video source in the spacing of the missing rows. When working with video caps, if one can capture two successive frames and then blend them in darken or lighten mode, there is no need to interpolate or dupe as with de-interlacing filters. <g>

I agree, motion blur can be of help as an alternative - but sometimes gaussblur does better even if it blurs in both directions, but it all depends on the image. Darken blend would be good to try, or lighten - depending on the missing lines luminance value.


Stephen Marsh.

[Flora]

Hi Stephen,

Thank you very much for your help...

I've read only very little on the De-Interlace Filter and you are absolutely right ....

Mine was just an experiment after having worked on Sanda's picture .... which was very small in size and which I strongly magnified as to see even the smallest changes in details .... Compared to the plain Lighten and nudge, it seemed smoother ... so ... in the heat of the moment ... I thought to share this .... but, later, trying it on a bigger sized picture, I couldn't see any difference either ....

I tried the 'Motion Blur' on another picture but, as often happens, the results vary from picture to picture, so, I wasn't very satisfied with that solution for that particular picture .... so, as you pointed out, good old 'Gaussian Blur' will be my Tool of choice for that kind of problem ....

Thanks again ....

I've already tried to delete this thread, but I'll have to bother someone of higher rank, since I'm not allowed to ...

[darkmke]

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

[Flora]

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!