38 replies to this topic

[Joooop]

Hello CN forums! First time here with an account, though I've arrived here a number of times from google searches regarding astrophotography.

 

So I got my first tracker a little over a week ago and I've tried shooting clear nights from my home since. I've just been practicing to get a hang of gear setup, polar alignment, focusing and target framing. Unfortunately, I live in a bortle 8-9 city (northern hemi) and my shooting locations are either a flat 1 story roof (with a small W / NW portion of the sky visible), my driveway with a smaller slice of S / SW due to trees / houses etc and a few spots in my backyard where I can make out polaris through some trees (up until last night, I didn't realize that my backyard had some decent S / SW view so my initial shooting attempts in that direction were from my driveway, pointing over a streetlight). I mention this because I'm definitely keeping my expectations modest since these are pretty bad shooting conditions. I'm just happy to get practice in whenever I can so when I get out for dark sky spots, I'll be slightly more prepared.

 

Gear:

- Camera: Fuji X-T20
- Lens: Fuji XF 55-200mm f3.5/4.8 @ 200mm (i've varied aperture from night to night)
- Tracker - SWSA pro 2i

 

**Bortle 8-9**

 

So after attempting a few targets that I can see from my location (Pleiades, Orion+Running+Horsehead+Flame, Flaming Star+Tadpole (I knew I wasn't going to see any cloud detail so this was purely for testing different shooting parameters and trying to locate the target), Rosette), I was able to progressively get better tracking and also seemingly fix my triangular star issue. My tracking got good enough for 1 minute exposures @ 200mm (I haven't tried exposing longer yet) and my focusing seemed to be working with a bahtinov mask.

 

Two nights ago I tried stopping down to f/7.1 on my lens and I got circular stars @ 60" -> https://imgur.com/a/7fQWsVP compared to my first attempts at f/5.6 which gave heart shaped stars @ 25" in the same direction throughout the image -> https://imgur.com/a/dqXmssQ . I know the stars are still not perfect but I think it's not bad for 1min without guiding.

 

Also after my second attempt, I realized my camera had auto-white balance set on as well as auto dynamic range. I set WB to daylight and DR to whatever the first default was, so it wouldn't fluctuate. For all my attempts, I've had long exposure noise reduction off.

 

I set up my SWSA with a shutter cable to shoot instead of my remote intervalometer so I could make use of the mounts RA dithering on my three most recent attempts.

 

Now I'm just dealing with one final issue which is rainbow rings / gradients that seem to be centered in my frame. I'm thinking has to do with my light pollution + shooting around other light sources + my lens being a zoom lens. When I shot Orion+friends and the rosette, I was shooting S / SW right over a streetlight. Pleiades/Flaming Star attempts were from my roof on my backyard side and didn't have anything like a really close streetlight to deal with but normal neighbors garage lights down low. I see the effect in both, right now I'm thinking it could be the combo of light pollution + these sources. I have shot flats for each attempt and below I compare quick auto stretches with and without flats. In photoshop I can use the dust / scratches filter to combat them to a certain extent but making sure any nebulosity isn't lost is very hard.

 

I should note my first two sessions here were with a UV filter on my lens. Since I wasn't sure if that was the culprit, I've been removing it for my more recent tries. I also used the stock lens hood for all but one of my attempts (I forget which target I didn't have it on for). Three nights ago, since I was shooting the rosette over a streetlight, I made a makeshift light shield with a tube of poster board on the end of my lens hood.

 

Here are some examples (For these, I'm mainly using siril for quick stacking and autostretching to compare with and without flats. I also have an autosave.tif from stacking with DSS but in all of those I stacked with flats). The quick siril compare shot process is color calibrate bg / highlights > remove green noise > autostretch histogram > bg extraction:

 

Pleiades

- 200mm, f/5.6, ISO 800, 191x25" lights
- 56 bias, 62 darks, 64 flats
- Flat acquisition: not ideal, I wasn't too careful about not changing focus / zoom and I didn't rubber band my shirt tight
- No dithering
- Waning crescent moon (1%) Bortle 8-9

 

Single light: https://ibb.co/xHWQphV

Single flat: https://ibb.co/pRybJBd

Siril autostretch with flats: https://imgur.com/a/DnZzkFl

Siril autostretch with flats + BG extraction: https://imgur.com/a/3alHSmp

Siril autostretch without flats: https://imgur.com/a/tKDTJl1

Siril autostretch without flats + BG extraction: https://imgur.com/a/qG6s88T

Background gradient shown after Photoshop dust & scratches filter on DSS stack w/ flats: https://ibb.co/2c0PfKs

 

Orion and friends

- 200mm, f/5.6, ISO 1600, 124x45" lights
- 40 bias, 29 darks, 51 flats
- Flat acquisition: not ideal, I wasn't too careful about not changing focus / zoom and I didn't rubber band my shirt tight
- No dithering
- New moon (0%) Bortle 8-9

 

Single light: https://ibb.co/5sJssfQ

Single flat: https://ibb.co/fXh6VHF

Siril autostretch with flats: https://imgur.com/a/g8dJGGF

Siril autostretch with flats + BG extraction:https://imgur.com/a/SijXWBk

Siril autostretch without flats:https://imgur.com/a/vaf879G

Siril autostretch without flats + BG extraction:https://imgur.com/a/c0PO8s7

Background gradient shown after Photoshop dust & scratches filter on DSS stack w/ flats:https://ibb.co/VNZX5s2

 

Flaming Star
Again, I'll say I was not expecting to catch any nebulosity with my gear / shooting location. It was almost getting dark and I wanted practice framing something that I could see West, from my roof so I quickly found an object without researching what it would take to acquire.

 

- 200mm, f/5.6, ISO 1600, 135x60" lights
- 50 bias, 0 darks, 50 flats
- Flat acquisition: slightly better, took care to not bump the lens at all.
- RA dithering (0.75 arcmin) via SWSA mount app
- Waxing crescent moon (15%) Bortle 8-9

 

Single light:https://ibb.co/9c6xY6V

Single flat:https://ibb.co/dDJfFKH

Siril autostretch with flats:https://imgur.com/a/YkGmJ1r

Siril autostretch with flats + BG extraction:https://imgur.com/a/aXCDIq1

Siril autostretch without flats:https://imgur.com/a/FXJOr71

Siril autostretch without flats + BG extraction:https://imgur.com/a/hQXE0Sp

Background gradient shown after Photoshop dust & scratches filter on DSS stack w/ flats:https://ibb.co/wwRT9NM

 

Rosette
At this point I was worried my lights from previous nights were overexposed so I went to ISO 800. I also stopped down my aperture a few more ticks to try and drastically combat my star coma issue.

 

- 200mm, f/7.1, ISO 800, 90x60" lights
- 45 bias, 0 darks, 45 flats
- Flat acquisition: the most careful I've been yet to not bump anything.
- RA dithering (0.75 arcmin) via SWSA mount app
- Waxing crescent moon (30%) Bortle 8-9

 

Single light:https://ibb.co/sWG2hPY

Single flat:https://ibb.co/F5x2FnK

Siril autostretch with flats:https://imgur.com/a/fLnqn7D

Siril autostretch with flats + BG extraction:https://imgur.com/a/cgSBlZq

Siril autostretch without flats:https://imgur.com/a/GQ2l51R

Siril autostretch without flats + BG extraction:https://ibb.co/k9qW9S8

Background gradient shown after Photoshop dust & scratches filter on DSS stack w/ flats:https://ibb.co/cL1YYP3

 

-------

So those were first 4 decent acquisition attempts from this past week or so. For flats, I'm using the tshirt + screen method, here are some pics of my setup > https://imgur.com/a/Y7exmq0 . Only one layer of fabric is being used around the lens hood. On the last two attempts, I put my camera in aperture priority with the exposure dial set to 0. The screen is an iPad at 100% brightness on a white screen. I do have a paper-like screen protector on the ipad that creates rainbow noise to the naked eye. Maybe I should try a different light source.

 

After some searching, I realized that I should have turned my LCD off for acquisition. I know this is obvious but I think up until this point I only did it for my Flaming star attempt.

 

At this point, I created a reddit thread on /r/askastrophotography for advice (it was basically identical to the text here): https://www.reddit.c...ings_gradients/ A fellow fuji shooter brought up a quirk with the camera doing analog -> digital conversion at different ISOs (?), saying that they experienced rings at ISOs of 800+. With that tip, I shot orion again last night at ISO640, f/7.1, 200mm for 60" exposures. Unfortunately I still ended up with the rings:

Orion+Friends ISO640 re-attempt

On this night I figured out I had a few spots in my backyard where I could still polar align and have a wider view of the skies to the south. Once my target went behind a tree after 2 hours, I moved my setup to the backyard to get another hour of data, this time without a streetlamp directly ahead and much fewer close light sources in general.

 

- 200mm, f/7.1, ISO 640, 103x60" lights *

- 40 bias, 35 darks, 40 flats

- Flat acquisition: careful not to alter the lens / camera set up.

- RA dithering (0.75 arcmin) via SWSA mount app

- Quarter Moon Bortle 8-9

* 103 total lights, 2/3 from imaging behind a streetlamp, ~1/3 from my backyard with less outside light sources.

Siril autostretch with flats and all of the lights combined: https://imgur.com/a/1hHQ8Qs

Siril autostretch with flats but only with the lights from the backyard: https://imgur.com/a/T5cbThQ

 

So yeah, sorry for the wall of text. I tried including as much helpful information as possible. I'm hoping it's just a product of my shooting location being bad for light pollution and other closer light sources. That being said, if I could try out any techniques to minimize this, that'd be great. I know dark sky locations are ideal but I'd still like to come up with the best data possible from nights when I'm not able to get out. Editing these rings out is really tough.

Even though the moon is getting brighter, I still want to image tonight to test out a lower ISO. Not too concerned about capturing a nice image with good data right now. I just want to figure out a way to reliably avoid these artifacts.

 

** I know a hosted jpg isn't ideal if you want to see the full range of a given RAW / TIF file so let me know if you'd like me to upload an original file to google drive to better investigate.

Edited by Joooop, 22 March 2021 - 12:24 PM.

[sharkmelley]

First of all, welcome to Cloudy Nights!

 

You're right about the wall of text 

 

The raw files are key to understanding these kinds of problems.  Let's take the final image for example, Orion+Friends ISO640 re-attempt.

 

Would you upload a single raw light and a single raw flat for that image to a file sharing site. I'll then take a look.

 

Mark

[Joooop]

First of all, welcome to Cloudy Nights!

 

You're right about the wall of text 

 

The raw files are key to understanding these kinds of problems.  Let's take the final image for example, Orion+Friends ISO640 re-attempt.

 

Would you upload a single raw light and a single raw flat for that image to a file sharing site. I'll then take a look.

 

Mark

Thank you Mark!

Here are three stills from that session (2 lights and 1 flat): https://drive.google...iew?usp=sharing

I included a light from shooting near the streetlamp and a light from my backyard with very minimal outside light sources.

Edited by Joooop, 22 March 2021 - 03:52 PM.

[sharkmelley]

Thank you Mark!

Here are three stills from that session (2 lights and 1 flat): https://drive.google...iew?usp=sharing

I included a light from shooting near the streetlamp and a light from my backyard with very minimal outside light sources.

Thanks for those raw files.  I'm not familiar with Fuji and I wasn't able to debayer them in PixInsight because of the X-Trans bayer pattern so I used RawDigger to do so.

 

Here are the three files together with blue channel divided by green and green channel divided by red (all bias subtracted):

 

 

The rings are very obvious both in the lights and the flat.  To my mind it is quite conclusive that some in-camera raw data processing is happening.  The question is what?  It might be some kind of lens correction but I looked in the EXIF and it gave no information on whether any corrections were set in the camera menu.  However the EXIF does contain a set of lens vignetting parameters and it is possible these have been applied to the raw data.  Try switching off everything lens related in the camera menus such as peripheral illumination correction, color shading correction, distortion correction. As a diagnostic procedure on other cameras, some people have tried taping over the lens electrical contacts so the lens is no longer recognised by the camera - the trouble is that a "fly-by-wire" lens may no longer operate.

 

These kinds of camera issues are certainly very frustrating!

 

Mark

[Joooop]

Thanks for those raw files.  I'm not familiar with Fuji and I wasn't able to debayer them in PixInsight because of the X-Trans bayer pattern so I used RawDigger to do so.

 

Here are the three files together with blue channel divided by green and green channel divided by red (all bias subtracted):

 

FujiXT20_Rings.jpg

 

The rings are very obvious both in the lights and the flat.  To my mind it is quite conclusive that some in-camera raw data processing is happening.  The question is what?  It might be some kind of lens correction but I looked in the EXIF and it gave no information on whether any corrections were set in the camera menu.  However the EXIF does contain a set of lens vignetting parameters and it is possible these have been applied to the raw data.  Try switching off everything lens related in the camera menus such as peripheral illumination correction, color shading correction, distortion correction. As a diagnostic procedure on other cameras, some people have tried taping over the lens electrical contacts so the lens is no longer recognised by the camera - the trouble is that a "fly-by-wire" lens may no longer operate.

 

These kinds of camera issues are certainly very frustrating!

 

Mark

Thank you for examining the RAW files.

So I just thumbed through my settings and there are two lens-related settings.

1) 'Lens modulation optimizer' was already set to OFF.

2) 'Mount Adapter Setting' / 'Shoot without lens'. Currently I have 'Shoot without lens' set to ON, so my 'Mount Adapter Setting' is set to a default value but I don't think it plays a role since I'm using a Fuji X lens that is compatible with the system. Judging by this page on the setting: http://fujifilm-dsc....adaptor_setting the options here only take affect when a lens outside of fuji is used with an M adapter. The tweaks you mentioned I look out for are greyed out. Maybe If I tape the contacts they would be changeable here and I could turn all of the corrections off manually.

Also I should add that I've been outputting in the uncompressed RAW format this entire time, and not fujis 'lossless compressed' option.
 

Edited by Joooop, 22 March 2021 - 06:16 PM.

[Joooop]

So I just found this thread and it seems these people came to the same conclusion about lens corrections being automatically applied to RAWs: https://www.dpreview.../thread/4261884

I'm thinking now, should I be able to remove all of these corrections in my RAW files in lightroom before stacking?

Looks like the profile is being detected in lightroom but I can't seem to disable them, only reapply a custom one.

Edit: and I just tried taping the lens contacts but unfortunately I cannot focus or change aperture (since this lens has a free range aperture dial and not fixed to certain stops).

Edited by Joooop, 22 March 2021 - 06:30 PM.

[sharkmelley]

The distortion correction discussed in that thread will not be applied to the raw image data but the vignetting might be.  However it's certainly the case that the parameters describing the corrections needed for lens distortion, chromatic aberration and vignetting are in the raw file's EXIF header:

 

 

Your raw files all had visible vignetting so it's more likely that the concentric rings are not caused by a vignetting correction but by some undocumented correction. It's certainly the case with Canon, Sony and Nikon mirrorless cameras that the correction(s) causing the rings is undocumented and therefore impossible to user to disable.

 

Mark

Edited by sharkmelley, 23 March 2021 - 02:39 AM.

[Joooop]

So do you think it'll be possible for me to use a 3rd party application to remove any of these settings or am I screwed?

Edited by Joooop, 22 March 2021 - 08:51 PM.

[sharkmelley]

So do you think it'll be possible for me to use a 3rd party application to remove any of these settings or am I screwed?

If I'm correct that the cause is an undocumented in-camera manipulation of the raw image data then there is nothing you can do except complain to Fuji and attempt to work around the problem.

 

Here are a few of tried and tested workarounds:

• Use a legacy lens with no electronic contacts.  If the lens is unrecognised by the camera firmware then it's possible the "correction" may not be applied.  This approach works for Sony mirrorless cameras but not for Nikon or Canon mirrorless cameras.
• Use the highest bit depth.  This is typically 14bits. Don't allow the camera to use a lower bit depth e.g. 12 bits.
• Avoid lossy compression
• Use a higher ISO.   On the Canon EOS Ra an ISO of 800 or more makes the concentric rings go away.  On other cameras it is not a complete solution.
• Try to "drown out" the ring pattern with signal and noise i.e. for your lights use a combination of exposure length and high ISO that puts the peak of the back-of-camera histogram at the halfway point.  For your flats, expose so the back-of-camera histogram is well over to the right.  This approach works well for Sony and Nikon mirrorless cameras.  But it didn't work well on the Nikon DSLR rings caused by lossy data compression.

So you can see that the workarounds are a bit hit and miss, varying quite a lot from manufacturer to manufacturer.  Unfortunately, it's possible that none of these workarounds will be successful for the Fuji.  It depends on the exact cause of the concentric rings.

 

Mark

Edited by sharkmelley, 23 March 2021 - 06:35 AM.

[Joooop]

If I'm correct that the cause is an undocumented in-camera manipulation of the raw image data then there is nothing you can do except complain to Fuji and attempt to work around the problem.

 

Here are a few of tried and tested workarounds:

• Use a legacy lens with no electronic contacts.  If the lens is unrecognised by the camera firmware then it's possible the "correction" may not be applied.  This approach works for Sony mirrorless cameras but not for Nikon or Canon mirrorless cameras.
• Use the highest bit depth.  This is typically 14bits. Don't allow the camera to use a lower bit depth e.g. 12 bits.
• Avoid lossy compression
• Use a higher ISO.   On the Canon EOS Ra an ISO of 800 or more makes the concentric rings go away.  On other cameras it is not a complete solution.
• Try to "drown out" the ring pattern with signal and noise i.e. for your lights use a combination of exposure length and high ISO that puts the peak of the back-of-camera histogram at the halfway point.  For your flats, expose so the back-of-camera histogram is well over to the right.  This approach works well for Sony and Nikon mirrorless cameras.  But it didn't work well on the Nikon DSLR rings caused by lossy data compression.

So you can see that the workarounds are a bit hit and miss, varying quite a lot from manufacturer to manufacturer.  Unfortunately, it's possible that none of these workarounds will be successful for the Fuji.  It depends on the exact cause of the concentric rings.

 

Mark

Thank you so much for all your help, Mark. I guess I'll contact fuji to see if anything could be done but I doubt that'll go far.

I've been considering upgrading this lens to a different fuji telephoto, maybe the results will be different too. I might try to ask other AP shooters with the same / similar camera gear to see if they experienced this phenomenon and have any workarounds.
 

[Kevin_A]

Thank you so much for all your help, Mark. I guess I'll contact fuji to see if anything could be done but I doubt that'll go far.

I've been considering upgrading this lens to a different fuji telephoto, maybe the results will be different too. I might try to ask other AP shooters with the same / similar camera gear to see if they experienced this phenomenon and have any workarounds.
 

I use the Nikon z6 and z7 mirrorless cameras and follow Marks prior advice regarding the circles as the nikon mirrorless have it too. I get rings on photos of individual galaxies worse than photos of diffuse nebulas or milky way shots where the whole image is full of many objects and uniform as opposed to lots of stars with 1 or 2 brighter objects like galaxies. You can test that out yourself and see if it is an issue for you. I shot tests with a 360mm for galaxies and 85mm and smaller for nebulas where no hard circles appeared. Good luck!

[Joooop]

I use the Nikon z6 and z7 mirrorless cameras and follow Marks prior advice regarding the circles as the nikon mirrorless have it too. I get rings on photos of individual galaxies worse than photos of diffuse nebulas or milky way shots where the whole image is full of many objects and uniform as opposed to lots of stars with 1 or 2 brighter objects like galaxies. You can test that out yourself and see if it is an issue for you. I shot tests with a 360mm for galaxies and 85mm and smaller for nebulas where no hard circles appeared. Good luck!

Thank you! Definitely going to try out many different configurations. Very possible it's a brightness thing too.

[sharkmelley]

Thank you! Definitely going to try out many different configurations. Very possible it's a brightness thing too.

If you want to investigate further then you can take a series of flats at different exposures to examine the ring patterns.

 

For example, the Nikon Z6:

• https://www.cloudyni...-4#entry9641613

And Canon EOS Ra:

• https://www.cloudyni...on-ra-testing/ 

Mark

[Joooop]

If you want to investigate further then you can take a series of flats at different exposures to examine the ring patterns.

 

For example, the Nikon Z6:

• https://www.cloudyni...-4#entry9641613

And Canon EOS Ra:

• https://www.cloudyni...on-ra-testing/ 

Mark

Interesting threads! I'd definitely like to take a variety of flats to see if it could help narrow anything down.

Do you think it would be a decent approach to try ISO 200, 400, 800, 1600, 3200 each taken with aperture priority exposed to ~1/3, 1/2 and ~2/3 of the histogram?

[sharkmelley]

Interesting threads! I'd definitely like to take a variety of flats to see if it could help narrow anything down.

Do you think it would be a decent approach to try ISO 200, 400, 800, 1600, 3200 each taken with aperture priority exposed to ~1/3, 1/2 and ~2/3 of the histogram?

No, to start with choose a single (low) ISO and then take a series of flats from very underexposed to normally exposed.  This is because these artefacts are generally easier to see at low ISO.  Then afterwards the same thing can be done at additional ISOs.

 

Mark

[Joooop]

No, to start with choose a single (low) ISO and then take a series of flats from very underexposed to normally exposed.  This is because these artefacts are generally easier to see at low ISO.  Then afterwards the same thing can be done at additional ISOs.

 

Mark

Ah, okay. I'll give ISO 200 a shot first, then. Thanks!

[sharkmelley]

I'm happy to take a look at them if you upload to a file-sharing site.

[Joooop]

I'm happy to take a look at them if you upload to a file-sharing site.

Thank you so much, Mark.

Here are the flats: https://drive.google...iew?usp=sharing

Taken at f/7.1, ISO 200, 200mm and on aperture priority at the following exposure stops: -3.0, -2.6, -2.3, -2.0, -1.6, -1.3, -1.0, -0.6, -0.3, -0.0, 0.3, 0.6, 1.0

For acquisition I mimicked my current setup but used a sheet of paper in place of a t-shirt, pictured here from the original post: https://imgur.com/a/Y7exmq0

Edited by Joooop, 25 March 2021 - 12:34 PM.

[sharkmelley]

Here are the flats: https://drive.google...iew?usp=sharing

I need to make a big correction. 

 

My diagram in post#4 is totally wrong. Because of the difficulties in debayering the X-Trans colour filter array (which I eventually did using RawDigger) I accidently ended up dividing two integer channels instead of converting to floating point before dividing.  This introduced a whole lot more artefacts into the image. 

 

The corrected version is here - this is ISO 640:

 

 

Distinct rings are still visible in the lights when dividing one channel by another but not visible in the flat.

 

 

This is confirmed by the set of ISO 200 flats at different exposures you uploaded just now - they all look pretty much the same as the ISO 640 flat. Here is one example:

 

 

So this leaves us with a mystery.  Why are the rings visible in the lights but not in the flats?  At the present time I haven't a clue.

 

Mark

Edited by sharkmelley, 25 March 2021 - 05:12 PM.

[Joooop]

Interesting....

Maybe I should thumb through any settings in my camera? I'm pretty sure I have everything imaginable on some sort of default / non-destructive setting. I was also planning on testing my 23mm fuji lens on the next available night (which I still will) but this discrepancy between the light and flat makes me think it isn't lens related?

Would even more exposure configurations on the lights lead to more info possibly? I can send over lights from other nights (iso800 + 25", iso1600 + 45", iso1600 + 60" etc) if that would help.

Edited by Joooop, 25 March 2021 - 05:47 PM.

[sharkmelley]

Would even more exposure configurations on the lights lead to more info possibly? I can send over lights from other nights (iso800 + 25", iso1600 + 45", iso1600 + 60" etc) if that would help.

Yes, I'm happy to take a look.  It might help.

 

Mark

[Joooop]

Yes, I'm happy to take a look.  It might help.

 

Mark

Thank you very much: https://drive.google...iew?usp=sharing

There's a chance I can shoot again tonight. Going to try my 23mm for a few test lights and also my 55-200, maybe at different focal lengths / narrower apertures and shorter exposures.

[sharkmelley]

Thank you very much: https://drive.google...iew?usp=sharing

One of those images was very interesting indeed:  Orion-f6.4_iso800_60sec.RAF

 

I opened it in Photoshop with the white balance to make the background grey and with both vibrance and saturation turned up high to emphasise the problem:

 

 

Now look at the histogram of the raw data from RawDigger:

 

[Click on image for larger version]

 

There is a series of sharp peaks in the histogram of each colour channel which correspond to the rings seen in the Photoshop image.  These sharp variations in each histogram cannot happen be accident.  Something very strange is happening.  It either means that both Photoshop and RawDigger are decoding the file incorrectly (which is very unlikely) or the camera is doing something very strange to the raw data.  I don't have any explanation for this behaviour. 

 

Mark

Edited by sharkmelley, 26 March 2021 - 10:41 AM.

[Joooop]

So I just went through all of my menus yet again and noticed this in the online manual


I had this OFF originally and just now turned it on. *Theoretically* I don't think it should change anything since my red eye removal setting has been off and is tied to flash configuration in the first place. That being said, there might be a chance that the relatively brightly exposed light polluted sky is triggering some kind of red eye processing? Really wish they were more descriptive with these settings.

Looking forward to trying this out, even for just a few light frames whenever I can. If it's the culprit I would feel like such an idiot.

Edited by Joooop, 26 March 2021 - 11:41 AM.

[sharkmelley]

It's nothing to do with red-eye removal.

 

The rings are definitely related to those steps in the histogram.  All of your lights have those histogram steps except the one that is 25sec and the one that is ISO 200.  None of your ISO 200 flats had the steps.  I'm beginning to think that only long exposures at higher ISO are affected. 

 

If you want to test this then do the following:

• 25sec, 30sec, 45sec exposures at ISO 200
• 25sec, 30sec, 45sec exposures at ISO 400
• 25sec, 30sec, 45sec exposures at ISO 800

In each case adjust the aperture so the histogram peak is halfway or less.  As always, I'm happy to examine them.

 

Mark

Edited by sharkmelley, 26 March 2021 - 01:26 PM.