Strange geometric pattern appears when I merge layers for a star trail image -Help

WolfHeart

New member
I opened 240 images as layers in Photoshop from Lightroom after basic editing and started from the bottom layer up applying lighten blend mode and masking out any unwanted light streaks till the top layer. when I apply merge layers/merge visible layers/Flatten a weird geometric circular pattern appears across the image on the sky and foreground.

I reset my images in Lightroom as I read that lens distortion and sharpening can cause this and to do the adjustments after merging, so images are dngs straight from camera, when I merged them the pattern appeared again but was more uniform like a checkerboard. I tried another set of 30 images and same patter appeared.

Does anyone have a solution for this? I have attached an image after merging, you can see the pattern clearly in the highlight area of the image. I also tried exporting jpg and using startrails software, got same results.

any ideas?
merged_trail_image.jpg
 
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Horoscope Fish

Senior Member
I opened 240 images as layers in Photoshop from Lightroom after basic editing and started from the bottom layer up applying lighten blend mode and masking out any unwanted light streaks till the top layer. when I apply merge layers/merge visible layers/Flatten a weird geometric circular pattern appears across the image on the sky and foreground.

I reset my images in Lightroom as I read that lens distortion and sharpening can cause this and to do the adjustments after merging, so images are dngs straight from camera, when I merged them the pattern appeared again but was more uniform like a checkerboard. I tried another set of 30 images and same patter appeared.

Does anyone have a solution for this? I have attached an image after merging, you can see the pattern clearly in the highlight area of the image. I also tried exporting jpg and using startrails software, got same results.

any ideas?

It would help, I think, to be able to review a full resolution version of the image but in looking at your posted .jpg in Photoshop I'm not seeing the, "weird geometric circular pattern" you describe.

What I do see, however, are what appear to be moiré patterns. Some of the strongest moiré I found was immediately adjacent to what I'm guessing is the doorway of the observatory(?), near the bottom of the image toward the left edge. If that's what you're talking about, I can only hope someone has a suggestion for preventing it from happening in the first place because removing moiré patterns is a stone-cold b--ch in my experience; usually involving a process of adding noise, and or a blur filter, to the image in an attempt to hide the patterns.

The only thing I can think of that might help, and it's a mighty stretch, would be processing in 16-bit mode, which assumes you're not already doing that. Another possibility is the issue lies with the color gamut you're processing in (eg. ProPhoto vs. aRBG vs. sRGB); but that's another stab in the dark.
 

hark

Administrator
Staff member
Super Mod
Contributor
It would help, I think, to be able to review a full resolution version of the image but in looking at your posted .jpg in Photoshop I'm not seeing the, "weird geometric circular pattern" you describe.

What I do see, however, are what appear to be moiré patterns. Some of the strongest moiré I found was immediately adjacent to what I'm guessing is the doorway of the observatory(?), near the bottom of the image toward the left edge. If that's what you're talking about, I can only hope someone has a suggestion for preventing it from happening in the first place because removing moiré patterns is a stone-cold b--ch in my experience; usually involving a process of adding noise, and or a blur filter, to the image in an attempt to hide the patterns.

The only thing I can think of that might help, and it's a mighty stretch, would be processing in 16-bit mode, which assumes you're not already doing that. Another possibility is the issue lies with the color gamut you're processing in (eg. ProPhoto vs. aRBG vs. sRGB); but that's another stab in the dark.

Paul, the star trails on the right half of the image appear to be a bunch of individual small squares that are joined together into long trails. It looks as if they are overly sharpened although that might not be the case.

WolfHeart, how long were the individual exposures before you merged them together?
 

WolfHeart

New member
here is a screenshot before the merge as u can see there is no patterns


screenshot_of_image_in_ps_before_merge.jpg



here is a cropped version of the image after the merge as u can see there is a strange pattern!
merged_trail_image2.jpg



[FONT=-apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Oxygen-Sans, Ubuntu, Cantarell, Helvetica Neue, sans-serif]Moiré occurs when you are photography a subject with repetitive patterns, this is different.

[/FONT]
 

hark

Administrator
Staff member
Super Mod
Contributor
here is a screenshot before the merge as u can see there is no patterns


screenshot_of_image_in_ps_before_merge.jpg



here is a cropped version of the image after the merge as u can see there is a strange pattern!
merged_trail_image2.jpg



Moiré occurs when you are photography a subject with repetitive patterns, this is different.


Oh - now I see what you're saying. Maybe some of the members who have merged star trail images will weigh in. It definitely resembles moire even though the individual image doesn't show it. Hmm....
 

WolfHeart

New member
I now am thinking its maybe a windows/graphics card issue because I tried to create an image from a set I did in 2014 that at the time produced a good image with no patterns and the strange pattern appeared! Back then I was using Windows 7 and an ATI card, now I use Win 10 and an Nvidia card. Also tried the same set now on a friends laptop that has an ATI card and image was much better but had some slight pattern appear in the shadow area of the image. So this has to be a graphics or operating system issue! :confused:

thank you for your input :)
 

Horoscope Fish

Senior Member
I now am thinking its maybe a windows/graphics card issue because I tried to create an image from a set I did in 2014 that at the time produced a good image with no patterns and the strange pattern appeared! Back then I was using Windows 7 and an ATI card, now I use Win 10 and an Nvidia card. Also tried the same set now on a friends laptop that has an ATI card and image was much better but had some slight pattern appear in the shadow area of the image. So this has to be a graphics or operating system issue! :confused:

thank you for your input :)
I spoke with someone who does pretty serious astro-photography and got their input regarding your issue. They confirmed what you're seeing is moiré. Their first suggestion, after seeing the image you posted here, was to disable any Lens Correction profiles you might be using in Lr or Photoshop as this is a known issue when doing star trails. The long answer had to do with reducing high frequency Bayer noise which I really wasn't following and, frankly, made my head hurt.

Suggested link: https://starcircleacademy.com/tag/moire/
 
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STM

Senior Member
Two things Photoshop does poorly, HDR (in fact it SUCKS) and creating star trails. I suggest you download Starstax and use it. It is free and it does an amazing job on star trail images.
 

WolfHeart

New member
I do use it but you know you think you'll get better results with processing raw. I am going camping in 10 days, hope I get better results this time!
 
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