Artifacts/banding in Star Trails

[NZPhotographyNZ]

Hi all.

Registered today as I really do need some help!

I recently was shooting star trails using my Sony A7Riii. Each exposure was 10 minutes (f/4, ISO400).

On my raw files, some of the star trails have banding, in that they are two different colours in a regular pattern. These are not gaps - the artifacts occur on individual raw files. Blending them in Photoshop makes the artifacts significantly more noticeable and ugly.

These have happened on some, but not all, trails. The occurrence is worst on the right side of the photo, but appears elsewhere to a lesser degree. Some star trails look fine. Also, interestingly, the very first photo I took (out of about 12-15) was the worst of all.

I have only done star trails once before this and did not have this issue but each exposure was 4 minutes not 10.



I have tried:

Loading to Photoshop direct from Lightroom, with and without any editing
Loading directly to Photoshop
Exporting as TIFF and then reintroducing to Photoshop
Using "enhance" to reduce artifacts - this does absolutely nothing
Changing from 8 to 16 to 32 bit
Have applied various blur filters but they don't seem to help much at all

Does anyone have any ideas?

Note, I was shooting with another Sony shooter on the same night, he has A7Riv. We basically did identical shots all throughout the evening. He did not have this issue in his raws.

Images below and also a link to photos.


100% crop of Raw


Some have the banding, some do not


First photo of the star trails series - worst of all!


Hot, hot mess after blending

Please find my Raw and edit at this link:

Loading…

www.dropbox.com

Please note, I am not super technical but would love to know why this happened and if I can prevent it in the future. Simple explanations would be greatly appreciated!

 

[No account anymore]

This is caused by the pixels and Bayer matrix, and would be the same for any camera using Bayer matrix sensors. The lower resolution sensor, the more jagging. Just very thin, high contrast lines at certain angles, are affected.

Brighter stars will fill more than a few pixels, so they look nice.

Also, turbulent air might make the same star trail sometimes vary a bit in different sectors.

Did you and your friend use the same lens and aperture? Probably not, since a higher Mp sensor would also show the same result for very thin star trails, but to a lesser extent. Focus precision might also make a difference.

One solution might be using a less sharp lens, or just let the lens be a tad out of focus. But then the result will depend on how the lens render in and out of focus aberrations.

When the image is scaled to normal viewing size, this is not a problem though. Just when doing pretty extreme pixel peeping.

Note that I use the A7rIII and other cameras for astrophotography myself, so this is a well-known issue.

 

[dth29]

I would agree, altough I don't have the RIII and haven't made star trails yet. Principally, that's Moire.

 

[Nusratty]

Do the trails look like that on the camera screen when you zoom in ? If so its raw processing in Lightroom. Did your friend shoot with the same lens ? Just trying to think of some of the variables, but it looks like Moire

 

[NZPhotographyNZ]

Did you and your friend use the same lens and aperture? Probably not, since a higher Mp sensor would also show the same result for very thin star trails, but to a lesser extent. Focus precision might also make a difference.

One solution might be using a less sharp lens, or just let the lens be a tad out of focus. But then the result will depend on how the lens render in and out of focus aberrations.

When the image is scaled to normal viewing size, this is not a problem though. Just when doing pretty extreme pixel peeping.

Note that I use the A7rIII and other cameras for astrophotography myself, so this is a well-known issue.

Thank you, I appreciate the time you took to reply.
The other time I shot trails, my stars were slightly out of focus so perhaps that is why I did not see the effect.

My friend and I used the exact same settings however different lenses. He used the 16-35mm f/2.8 GM and I used the 24mm f/1.4 GM. We are both really just learning so we were working it out together. His raw files however are significantly better than mine.

Yes, it doesn't look as bad scaled down but I would be loathe to ever really show this file enlarged.



Probably just need to try again!

 

[daran]

Does anyone have any ideas?

Note, I was shooting with another Sony shooter on the same night, he has A7Riv. We basically did identical shots all throughout the evening. He did not have this issue in his raws.

Maybe he is using Capture One? I am and had a quick go. There is a specific Moire tool in C1 and I also changed color noise and sharpening from their defaults. Looks noticeably better to my old eyes.

Images below and also a link to photos.


100% crop of Raw

100% crop

Please note, I am not super technical but would love to know why this happened and if I can prevent it in the future. Simple explanations would be greatly appreciated!

As others have said, this is Moire due to bayer sensor. There is nothing particularly wrong with the image, just inadequate processing (for this type of image).

I'm not sure how much difference it will make on the A7R3, but I'd experiment with either ISO100 (max DNR and max time in a single shot) or ISO640 (lowest high gain ISO). I'd also try shooting uncompressed RAW, as the extreme DNR of night shots is the weak point of the compressed RAW format.

 

[daran]

My friend and I used the exact same settings however different lenses. He used the 16-35mm f/2.8 GM and I used the 24mm f/1.4 GM. We are both really just learning so we were working it out together. His raw files however are significantly better than mine.

The difference may be that yours are significantly sharper. The easiest way to avoid Moire is to blur the image before capturing it. Hence the AA filter on most low resolution cameras. The A7R3 does not have an AA filter. So it is sharper but also more prone to Moire. It usually can be dealt with in post though, see my other response.