Any vignette neutralizer editing tools out there?

[Bytesmiths]

I've struggled with the vignetting tools… Below is the Olympus 75mm lens from f/1.8 to f/22 off a white card.

I've used such a technique for years — inverted luminosity mask of a "null frame" shot.

You need to "normalize" it by adjusting the curve so the darkest spot is 100% clear, and use it in "luminosity" blend mode, so it won't darken your entire image.

For example, I stitched 13 images to make this panorama. The problem is that I had horrible vertical banding, due to lens vignetting, which got progressively worse when two edges were overlapped.

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So I made an inverted luminosity mask that nearly totally eliminated the banding, to the point where I could print it 120" wide, to hang as a banner in our art festival booth. (I also disproportionally scaled it by about 5:1.)

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This was our table skirting for our art festival booth.

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[RAH]

I've used such a technique for years — inverted luminosity mask of a "null frame" shot.
...
You need to "normalize" it by adjusting the curve so the darkest spot is 100% clear, and use it in "luminosity" blend mode, so it won't darken your entire image.

Wow, what beautiful results with such a hard-to-fix start! I do have one question - did you use the inverted luminosity mask technique on EACH shot individually first, and then stitch all the edited shots together, or did you do the stitch first and then use the technique on the composite image? I think you almost surely used it on each shot first (much easier, I would think), but just want to know for certain.

 

[Bytesmiths]

did you use the inverted luminosity mask technique on EACH shot individually first, and then stitch all the edited shots together, or did you do the stitch first and then use the technique on the composite image?

I worked on the composite.

And sorry, I did not use the "null frame" technique I talked about, rather, I took a horizontal slice of the sky, where the effect was most noticeable, made a mask from that, then duplicated it down the height of the composite image. I then spent quite a bit of time tweaking the contrast and brightness of the mask.

In retrospect, it might have been easier to correct each frame first, but by that time, I had a lot of sunken time invested in the stitching! Next time, I'll try correcting the individual frames first.

 

[Mack]

I got in contact with the author of the ART program on the "IR Hotspot" matter.

His suggestion was "To use a 'Flat-Field' file to correct for the hotspot in ART." Specifically, this from RawTherapee: http://rawpedia.rawtherapee.com/Flat-Field

So I made a frosted filter from a piece of clear plastic (Lexan) and made it frosted with 220 and 400 grit wet-dry paper on both sides. I hold it close in front of the IR filter/camera setup and shoot a normally exposed shot of it at the light source which gives me a hotspot image alone. With that, I can use that image to apply the "Flat-Field" effect to whatever image I shoot in same lighting, lens distance, f/stop, etc. to eliminate the hotspot while not affecting the main image detail. It's basically an inverted image placed and blended over the main one. Aside, I have the Expo-Disc thing which might work but it vignettes corners being a bit thicker than the plain frost plastic against the lens.

Fwiw, the "Flat-Field" location in the ART software's editor is under the RAW icon (Shortcut is Alt+R) and it's the last item. For 'Flat-Field' File you pull up your IR hotspot made with the frosted plastic and Blur type set to Area. and Blur radius 200 and see how that works.

 

[laptoprob]

Just tried the Oly75 on my 720mn comverted GF6. No hotspot to be seen at any aperture! Even looking at a sunlit, high contrast scene.

 

[Mack]

Just tried the Oly75 on my 720mn comverted GF6. No hotspot to be seen at any aperture! Even looking at a sunlit, high contrast scene.

You must hava a freaky Olympus 75mm as it is known for hotspots according to KolariVision who has it listed as a "Poor Performer" under the heading "Micro Four Thirds Lens IR Hotspot Performance" in their database listed here. Maybe something going on with the GH6 sensor too.

I decided to try mine to see what was happening and what it looked like. Mine was indeed poor for hotspots as mentioned in the link ( https://www.mu-43.com/threads/any-vignette-neutralizer-editing-tools-out-there.110589/post-1454965 ) where I shot a plain white card and while stopping it down shows the hotspot becoming prominent. Sky shots were equally problematic.


Aside, I'm still waiting for Lifepixel to get me a used E-M1 camera THAT MECHANICALLY WORKS for full spectrum. Been almost three months now since I ordered one on Jan. 23. The last two both suffered the erratic rear shutter dial issue straight out of the box so they went back the same day in both cases. Rotating the rear shutter dial should change the speed, but sometimes it took maybe 12 clicks to move it one speed increment or not. Probably explains why they are "used" cameras too with that model. I need to call them and see what is going on and what the holdup is. Hope it isn't a "We got more bum E-M1 used ones with the same issue." Dunno. Maybe they will find a working used one this year. I won't hold it against them as it was a bad Olympus model with a lot of complaints about the erratic shutter dial matter on the web after I first got one. Olympus repair wanted $250 to fix them, but Lifepixel said parts weren't available so who knows.

 

[laptoprob]

checked again, hotspot appears from f8. Not at larger apertures.

 

[wjiang]

Astrophotography software such as DeepSkyStacker also have options for compensating for vignetting by supplying a flat frame.