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Author Topic: Hows my reflection noise reduction? I'm not yet happy with it,how do I do better  (Read 2084 times)
darlingm
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« on: July 08, 2012, 07:21:27 PM »
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I have been working on reducing reflection noise in several scans. All the white dots are due to reflection from the scanner's light, due to glossy oil paint being used and the canvas curvature.

Have I pushed it as far as it can go, or is better possible? (Without blurriness/blotchyness/etc.) I'm not yet happy with the results. Re-scanning or photographing is not possible.

Some areas are decent, but especially in the dark areas (around the yellow, and edge of the flower) have too light of specs still.

This is a small piece of one image, and there are many images. I need to find a way to do this without doing a ton of manual work. I certainly don't mind having to spend a bit of time on each image, but manually doing the entire 16,000x12,000 file and the others would take forever. Also, having to manually mask areas would take too much time.

The original piece was on canvas, however didn't have the amount of variation in my "After" image due to the canvas -- that's still due to the original reflection noise.

Is there a way to get a selection from detecting noise, and use a content-aware fill across the entire image, based on its surroundings? I'm finding the noise tools aren't working well for me. I've tried several third party de-noise programs as well.

EDIT: Don't mind having to get a third party program, doesn't have to be Photoshop or Lightroom.

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« Last Edit: July 08, 2012, 07:39:48 PM by darlingm » Logged

Mike Westland Printworks
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bill t.
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« Reply #1 on: July 10, 2012, 12:05:49 AM »
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Since the real experts have been silent, I will chime in.

Your noise reduced result is probably as good as you could get by any method.  It looks very clean to my eyes.

However, it has the problem that the subtle highlights that mark the texture of the paint have been removed along with the specular scanning highlights from the canvas gloss.   Such textural brushstroke features can be very important to painters and are sometimes essential to how an oil painting presents itself.  I have often noticed that otherwise technically excellent giclee prints where such highlights have been suppressed look rather lifeless compared to the originals.

For the few prints of canvas originals that I have made for friends, I have usually used light that simulates directional lighting coming from the top.  This is done by turning the painting sideways and using a distant spot with barn door off to the "top" side.  By playing with the barn doors it's possible to get very even lighting across the canvas.  My theory is, by creating textural highlights on the painting that are much stronger than the straight-on reflection from the scanner light, those highlights will survive the noise reduction process.  Of course the mid-afternoon Sun also can work quite well, provided you do not have color contamination from nearby colored surfaces like lawns, brick walls, etc.

Of course this mean photography, rather than scanning.  But by stitching together enough individual shots can you any resolution you require.  Of course color management will be a little more difficult.

Well, so I haven't said much that's useful here, but it should at least start the ball rolling.   Smiley

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darlingm
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« Reply #2 on: July 10, 2012, 01:01:17 AM »
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I appreciate the response.  I've been very concerned about losing any subtle details as well, and it helps to hear that it's good given the starting point.

I worked on it quite a bit more, and I'm a lot more happy with it now.  I'll still probably keep working on it.  I think I've kept it more in line with the original color, and the dark areas are looking a lot better.

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Mike Westland Printworks
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artobest
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« Reply #3 on: July 10, 2012, 07:11:01 AM »
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The new version looks softer ...
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louoates
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« Reply #4 on: July 10, 2012, 07:44:11 AM »
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When I was doing this sort of thing I would simply use the darken tool set on highlights and a large soft brush size and simply "paint" over whatever reflections seemed right for the image. It's was down and dirty but it worked fine for the price range the artist expected. I'd do it on a duplicate layer above the original one and use the opacity slider to mute the darkened highlights to taste.
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John Nollendorfs
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« Reply #5 on: July 10, 2012, 08:33:12 PM »
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Use the scratch & dust filter. Play with settings in the neighborhood or 2 to 4 pixels, and 20 to 40 settings. Does amazing removal of these spectral dots. Often I use the filter on local areas, to minimize softening effects.
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schrodingerscat
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« Reply #6 on: July 11, 2012, 12:31:15 PM »
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Accurately photographing flat artwork is difficult at best. Especially anything with pronounced texture.

Wondering why you used a scanner? The tried and true method is even lighting from two equal output sources at 45 degrees and equal distance, preferably diffused, with the camera centered and perpendicular, much like a copy stand. You can then visually work with the lighting to reduce specular reflections.

As stated, trying to do it with post production will have an impact on other areas of the image.
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