You should take a picture at every aperture setting, just to check out what the profile is doing with vignetting/distortion correction.
I’ve tried this with both the Sony 85/1.4 GM and the Sigma 85/1.4 DG DN, and the LR profiles for the Sony 85/1.4 appear to me to be much more even across the aperture range.
Latest version of LR on iPad.
As far as internal reflexes and veiling flare both lenses seem really good to me.
The distortion correction stretches the image of the Sigma 85/1.4 DG DN along the horizontal and vertical mid lines. Very little is cut off in the corners.
The lens does have a baffle on the back, it looks like that would impact the edges of the frame. Looks like it is where I would expect and eyballing the baffle looks symmetric. Looking thru the lens there is nothing obvious that would cause any asymmetry. Ok time to repeat test with other lenses.
Given that it's a well centered lens from a sharpness perspective, it seems like something else in the optical path is slightly misaligned. Whether it be the optics as a whole group, or the baffle, or the lens mount itself (relative to the optical group.)
I actually notice something like this with my 24-105. One corner shows slightly more vignetting than the other, but in general it seems relatively well centered.
tschopp wrote:
The lens does have a baffle on the back, it looks like that would impact the edges of the frame. Looks like it is where I would expect and eyballing the baffle looks symmetric. Looking thru the lens there is nothing obvious that would cause any asymmetry. Ok time to repeat test with other lenses.
Photos from the 35GM and 135GM. They show the same vignette asymmetry, darker on the top normal, darker on the bottom inverted. There is a fair bit of gradient in the sky to confuse issues. Captured a cloud to make sure rotation is correct (different cloud between lenses, 135 was closer to horizon).
The common item between the tests is the camera. I guess the only logical thing to do is sell the a7Riv and pickup an a1. I think there is another thread looking for proper justifications.
tschopp wrote:
...
You might try this approach with a 2x2 pano of non-galaxy to see if it improves stitching performance. I use sequator for astro stacking and have been pretty happy with it. I haven't tried astro pano, its hard to say if you will still see the ring structure because the quality of the photo in the center will increase so you will still have a difference in quality between the center of the shots and the corners.
Best of luck. I tend to use the 135GM for tele astro, the vignette on this lens is better than the 85DN, also less distortion....Show more →
Thanks for the comment. I agree that for this use case one is pushing the equipment to its limits and it might or might not work. Noise is relatively less of an issue, since due to using a tracker I am shooting at ISO800 which is very close to the second ISO gain at 640. I'd consider the approach you mentioned, but it would be too much work given the fact the single panorama already takes more than 1 hour to complete.
Most importantly though, as demonstrated here the lens is capable of performing well: https://www.fredmiranda.com/forum/topic/1712817/1#15962095
This was shot with a different copy of the Sigma 85mm F1.4 DG DN not showing any of the vignetting rings - (I bought and returned the lens once last year due to an unrelated problem with corner aberrations - this shot was made with that meanwhile returned copy). Camera and workflow were the same, so I still tend to believe there is copy variation with this lens.
DistantPlaces wrote:
Thanks for the comment. I agree that for this use case one is pushing the equipment to its limits and it might or might not work. Noise is relatively less of an issue, since due to using a tracker I am shooting at ISO800 which is very close to the second ISO gain at 640. I'd consider the approach you mentioned, but it would be too much work given the fact the single panorama already takes more than 1 hour to complete.
Most importantly though, as demonstrated here the lens is capable of performing well: https://www.fredmiranda.com/forum/topic/1712817/1#15962095
This was shot with a different copy of the Sigma 85mm F1.4 DG DN not showing any of the vignetting rings - (I bought and returned the lens once last year due to an unrelated problem with corner aberrations - this shot was made with that meanwhile returned copy). Camera and workflow were the same, so I still tend to believe there is copy variation with this lens. ...Show more →
I remember your other photo, it's photos like this that make me want to get a nice pano head. Since you are using a tracker then it's not the s/n problem I mentioned. Maybe a vignette correction that is specific to your lens camera system would help. When I do this I manual focus to infinity and shoot a piece of white paper illuminated by the sun (to provide uniform illumination). These vignette files only need to be done once. You could create one now with your lens/camera system and apply it to these images. I typically also shoot noise files, those should be done after the image is shot to capture sensor noise (I assume you turn off long exposure noise reduction).
I know sequator can use the vignette files, I suspect it could process a single image file as well as a stack of them. If it refuses, then just make a copy of your file and feed both files into sequator.
There is nothing like astro to discover the flaws and weakness of a lens.
tschopp wrote:
I remember your other photo, it's photos like this that make me want to get a nice pano head. Since you are using a tracker then it's not the s/n problem I mentioned. Maybe a vignette correction that is specific to your lens camera system would help. When I do this I manual focus to infinity and shoot a piece of white paper illuminated by the sun (to provide uniform illumination). These vignette files only need to be done once. You could create one now with your lens/camera system and apply it to these images. I typically also shoot noise files, those should be done after the image is shot to capture sensor noise (I assume you turn off long exposure noise reduction).
I know sequator can use the vignette files, I suspect it could process a single image file as well as a stack of them. If it refuses, then just make a copy of your file and feed both files into sequator.
There is nothing like astro to discover the flaws and weakness of a lens. ...Show more →
I'd like to hear more about this method! If there's any way to salvage some of my images, that would be great. As I don't want to further derail this thread from its originally mentioned issue, let me just PM you.
Update so I sent my lens over to Sigma for an evaluation. After describing the issue to them in the form they just told me this.
"Hello, we have received your lens and can not replicate the issue. Can you please send image samples so we can better understand the symptoms? Thank you!"
Mind you the agent that I sent the photos to before shipping the lens said that I wouldn't need to send the photos in the form I filled out for them to investigate the problem.
So I sent them some examples including a throwaway raw file that I will share here.
Another issue that I noticed was that the lens had a few specks of dust from cleaning the rear element. I asked them if they can check the seals and possibly remove them since it is advertised as dustproof.
Your issue is not the same as mine as described earlier in this thread, but I feel it might be related.
The update and Sigma US response is interesting.
Not sure how much this will help you but here are my follow up experiences:
I contacted Sigma support Japan and sent them my lens, along with several sample images. I also had sample images from copies which did not have the vignetting/donut ring problems I saw. It took a lot of explanation but they finally reproduced my issue in their factory. Long story short, here is their response: https://i.imgur.com/7FOm2TA.jpg
What I am concerned about is that I mostly shoot at F2.0 to control the corner aberrations more, but Sigma could not reproduce it at all at F2.0. So this special firmware is only compensating at F1.8/F1.6. The lens was just delivered yesterday but I'm about to leave for Christmas holidays and will only get around to test it after New Year.
Anyway, maybe it can help you refering to this case when following up with Sigma US.
DistantPlaces wrote:
Your issue is not the same as mine as described earlier in this thread, but I feel it might be related.
The update and Sigma US response is interesting.
Not sure how much this will help you but here are my follow up experiences:
I contacted Sigma support Japan and sent them my lens, along with several sample images. I also had sample images from copies which did not have the vignetting/donut ring problems I saw. It took a lot of explanation but they finally reproduced my issue in their factory. Long story short, here is their response: https://i.imgur.com/7FOm2TA.jpg
What I am concerned about is that I mostly shoot at F2.0 to control the corner aberrations more, but Sigma could not reproduce it at all at F2.0. So this special firmware is only compensating at F1.8/F1.6. The lens was just delivered yesterday but I'm about to leave for Christmas holidays and will only get around to test it after New Year.
Anyway, maybe it can help you refering to this case when following up with Sigma US....Show more →
Wow, I wonder how many other owners might have this same issue. I hope it's resolved for you by F/2. Do update us when you do have a chance to test it out. I haven't shot with it yet for astro. I appreciate you coming here and sharing this information. Enjoy Christmas and stay safe.
Update! "Hello, Please see the comparison images below. The artifact created on the right image is from having the camera’s lens compensation/shading compensation on. The service manager took the lens and ran tests to help with this issue. Also, the artifact in jpeg format instead of raw is far more noticeable. Please turn of the shading compensation function in camera. We can clean out the dust in rear and front element. Thank you!"
I'm a bit disappointed, to be honest. The profile should have corrected it. Now I have to turn it on and off each time I swap lenses. Now I have to deal with even darker corners. No mention of if there's an issue with the seals so they will just go along and clean it. What happens if it happens again? I have to keep sending it out each time it happens. Granted I'm only 1 year into the warranty. So I wonder how much it'll be for them to service it once the warranty expires? I suppose by then I'll upgrade to the 85mm F/1.2 GM. I'm curious if the rendering vs the future GM will have any redeeming quality about it to keep it as a backup lens. I'd like to thank everyone that contributed to this thread. I hope that it will help someone else in the future.
"Hello, My manager said he used a variety of apertures and the results were the same. A lot of contrast/exaggeration was used in our example to show you how the corners will look. So in general the corners are not that dark with a normal contrast setting. Shading compensation is really not necessary with this telephoto lens. All lenses are checked for decentering/resolution. That is controlled by shims and will be put back the way it was before. Elements are in groups of glass and this cleaning does not require major disassembly. The lenses are dust/weather resistant not 100% dust/weather proof. Some dust in a lens is natural even in the sports/arts series. I’m not sure how this was worsened by your cleaning method if you used a rocket blower as opposed to compressed/canned air. I’m not sure you created dust in the lens. We are working on the cleaning for the next couple of days and will send it back to you then. Thank you!"
I think there is another thread looking for proper justifications.
