[cdd29]

Long story short, I thought I'd take advantage of some haze the other night & try to take some pics of visible beams of a rotating light beacon at the airport. Similar to what a lot of people do with light houses (closest lighthouse is about 7 hours away, so this will have to do.) Anyway, finally got everything to stack & merge after several problems (PS doesn't like to stack for some reason for me) but there's tons of artifacts in the final image: rings & what looks like a moiré pattern. No optical filters were used which should rule out newton's rings. There were no artifacts in the individual images, or even if you look at the layers merged together in photoshop, only in the final image after all layers are merged. So what are they? I'm wondering if the circles are atmospheric phenomenon similar to moon/sun dogs that are so faint they aren't visible in the individual shots (I'll have to look again at the individual pics later tonight after work closer to see if there is any trace of halos). Someone suggested these might be a result of the bulb/array itself in the beacon, being LED instead of tungsten. That theory makes a little sense as the camera for whatever reason used electronic shutter instead of mechanical as I usually have it set to. This is about 20 shots stacked, 1/4", f/2, ISO 4000 (beams weren't very visible at lower ISO). My theory is they're some kind of artifacts from the stacking. My computer often does strange things when stacking & merging in Photoshop (skewed or flipped images, smears). Need to try this on my laptop to see if I get consistent results. Of the two shots, one is a single image (one of several) and the other is the final. Other than stacking, it's uncorrected & AWB was used.

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[nixxo2002]

it's a banding . usually it happens with electronic shutter with fast shutter speed . banding can be in color or horizontal light

You Tube

You Tube

video will explain in more details

[pacerr]

Might also note that airport rotating beacons have only white, green and yellow lighting combinations. Color balance may be off.

[Bob 256]

Looks really cool!

Might be something buried in the blacks of the individual images and when stacked caused the interference type pattern. Try lifting the blacks of a single exposure using curves and see if anything is there that's hidden in the darker sky. As said, it probably originated with the rolling shutter (ES) and maybe LED type light sources in the tower, exhibiting some kind of flicker that you wouldn't see visually. Stacked, the subtle unseen patterns could then create the "interference" pattern of the resulting photo.

Did I say, looks really cool?

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Last edited by Bob 256; 12-01-2022 at 09:44 AM.

[cdd29]

The camera for some reason did use ES when doing the interval shooting (I don't normally use ES due to banding, rolling shutter, etc.) I don't think it's banding as that would be horizontal stripes and should show up in the individual frames. This is showing up as halos and a moiré pattern in the final image once merged. And actually the halos kinda look like diffraction patterns, looking at a high res version (the patterns got lost some when the shots uploaded), but this was shot at f/2 so diffraction shouldn't be an issue. Doesn't show up when you're looking at the image as layers. It was a fairly show shutter speed too (1/4") so that should diminish the effect.

Good suggestion on playing with curves in a single image. Tried that (even tried reversing the image) and nothing strange shows up. Someone on Faceplant suggested it might be the way Adobe is applying the lens profile to the raw files. I'm going to try stacking the jpegs and see what that does, which should rule out that.

The WB is off on the grass but pretty close on the tower & atmospheric parts of the image.

I'm checking with the airport & museum to see what kind of lighting the beacon uses.

Given problems I've had with PS stacking (artifacts, images skewed & flipped, ghosting) in the past, I'm thinking it's some weird result from that. However I can replicate it on my laptop as well, so it very well maybe something in the images. The halos could be a result of atmospheric conditions, similar to a sun/moon dog, but if that's the case why would it not show up in the individual files?

I even tried merging the files an an HDR. Looked like crap but none of the patterns show there. They don't show if I stack in Lightroom either (don't like the results LR produces), so whatever it is has to be the way PS is meshing everything together.

I don't know. I'll keep playing with this & reshoot it with a different camera. In the mean time the Photoshop guru at the local camera shot is very curious and is going to try to help figure this out. I'll report back.

[pacerr]

I'm curious as to why there's a beacon color discrepancy. Aviation lighting is dictated by FAR's. There's Fed standards for marine beacons too. Doubt that would affect banding though.

airport beacon at DuckDuckGo

[Grimmus]

I have had similar and it was due to applying lens correction to the images before stacking. Try stacking without applying the lens profile correction.

[cdd29]

I have had similar and it was due to applying lens correction to the images before stacking. Try stacking without applying the lens profile correction.

Apparently this was the case (someone also noted that on Faceplant). I stacked the jpegs and no artifacts. Just kinda strange that shows up in a final, stacked image instead of individual images. Mystery solved.