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Thread: Strange double image a7rII w Leica APO 50

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    Senior Member dchew's Avatar
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    Strange double image a7rII w Leica APO 50

    I'm sure there is a reasonable explanation for this but it escapes me. The other day I was hiking around Mont Blanc. Although the weather was mostly uncooperative, I did get up at 4 am during a break in the clouds and took a few nightscapes. This one is not very sharp, and upon closer inspection it looks almost like a double image. Here is the full frame:



    And here is a 100% crop. If you look at the star trails you can see two parallel lines for each one, brighter above, slightly dimmer below.



    First of all, please don't judge this on my lack of fine tuning noise reduction. I am new to this camera and have yet to find my comfort zone above base ISO. Here are the stats:
    RSS TV24 w/ just the swivel base; no ball head
    Sony a7rII
    Leica APO 50 summicron Asph
    f/4
    2 sec time delay
    10 sec exposure
    ISO 800
    - 1 ev exposure

    This cannot be camera shake because both star trails are continuous for each star. I think the camera would have to be oscillating quite fast between two identical positions for the entire 10 second exposure to produce this by shaking, no? I double-checked EXIF in Rawdigger - image stabilization was off. To confuse the issue more, here is another photo a few minutes later with the Loxia 35 f/2:



    And again a 100% crop.



    No double image. So whatever it is it was associated with that camera/lens combination. But I cannot get it to repeat the problem! I've taken several images this morning to verify the APO 50 is indeed still as sharp as you would expect with no "double images".

    It might be possible that I did not have the lens shade extracted. The moon was overhead but nowhere near the edge of the frame.

    Any thoughts?

    Dave
    How glorious a greeting the sun gives the mountains! - John Muir

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    Senior Member dchew's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Here is a 100% crop of a shot this morning testing the APO 50 with the a7r. No issues...



    Dave
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    Senior Member pegelli's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    How about an inadvertent but very small camera move after 4 or 6 sec into the 10 sec exposure. That would explain the double star trail with one being slightly brighter then the other.

    Edit: oops, senior moment, that would put a zig-zag in the star trail and not double it up, so my "theory" is incorrect.

    I'll keep thinking

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    Re: Strange double image a7rII w Leica APO 50

    It is shake from somewhere. Two exposures within that 10s.
    Either that or aliasing.

    Dave, Gorgeous scenes and they are not helping my AA50 lust.

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    Senior Member dchew's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by Vivek View Post
    It is shake from somewhere. Two exposures within that 10s.
    Either that or aliasing.

    Dave, Gorgeous scenes and they are not helping my AA50 lust.
    Thank you Vivek. One thing I forgot to mention: I have four shots taken right after each other at different ISO's (because at 4am after a long hike I couldn't remember what best ISO to use...). All of them have the same double image.
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    Senior Member dchew's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by pegelli View Post
    How about an inadvertent but very small camera move after 4 or 6 sec into the 10 sec exposure. That would explain the double star trail with one being slightly brighter then the other.

    Edit: oops, senior moment, that would put a zig-zag in the star trail and not double it up, so my "theory" is incorrect.

    I'll keep thinking
    At first I thought the same thing but you are right. It would jump during the trail and make a "Z" pattern. I'm still stumped. Vivek's aliasing comment is possible, but it looks to me like the entire image is this way, not just the stars. I could be wrong about that though...

    Dave
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    Administrator, Instructor Guy Mancuso's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Earthquake. Lol

    Kicked the tripod. Tough one here
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    Re: Strange double image a7rII w Leica APO 50

    Could actually not engaged that lens or the aperture jumped into place. It might be aperture ring
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    Re: Strange double image a7rII w Leica APO 50

    This may be an example of interreflections in the sensor stack...

    Try shooting a night shot again of the full sky. See if the offset is related to the angle from center axis, and operates radially. That won't prove it is interreflections, but it will prove it is optical rather than an odd offset that is happening.
    a7r, a7rII, FE 16-35, FE 24-70GM, FE 70-200, Loxia 21mm, 35mm, 50mm

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    Senior Member dchew's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by Guy Mancuso View Post
    Could actually not engaged that lens or the aperture jumped into place. It might be aperture ring
    I was wondering if I bumped that or the focus ring, but it is in all four shots and I think that would also look like a zig-zag.



    Quote Originally Posted by mjm6 View Post
    This may be an example of interreflections in the sensor stack...

    Try shooting a night shot again of the full sky. See if the offset is related to the angle from center axis, and operates radially. That won't prove it is interreflections, but it will prove it is optical rather than an odd offset that is happening.
    Interesting. I was thinking some sort of reflection would do it, but the sensor itself didn't occur to me. It seems to me it could only be reflections or IBIS gone whacky.

    I will have to wait until I travel home to do more tests, so perhaps early next week.

    Thanks for all the suggestions so far...

    Dave
    How glorious a greeting the sun gives the mountains! - John Muir

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    Re: Strange double image a7rII w Leica APO 50

    Quote:"I double-checked EXIF in Rawdigger - image stabilization was off."

    SteadyShot was really switched off, right? :-)
    At 4 AM I would forget that. :-(
    With best regards, K-H.

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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by dchew View Post
    I was wondering if I bumped that or the focus ring, but it is in all four shots and I think that would also look like a zig-zag.


    Interesting. I was thinking some sort of reflection would do it, but the sensor itself didn't occur to me. It seems to me it could only be reflections or IBIS gone whacky.

    I will have to wait until I travel home to do more tests, so perhaps early next week.

    Thanks for all the suggestions so far...

    Dave
    I have had the same kind of double startrails with the A7r. I think it is a camera/sensor movement. It is very short, but strong (think a jump), which would explain why there are no zigzag to see. IMO, the 2 sec. shutter delay isn't enough to prevent motion. Using a remote (either the remote app on the iPad, or the cable remote), took care of the problem for me.
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    Re: Strange double image a7rII w Leica APO 50

    so the length of the star trace is rotation of the earth during the exposure, and the double trace, roughly perpendicular to that, is the issue?

    jm

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    Re: Strange double image a7rII w Leica APO 50

    I would have guessed a filter issue. Did you use a filter?

    I've seen exactly this with a filter which had the front and back planes not perfectly parallel. This used to happen on filters from the 70's and earlier very frequently, with Tiffen and Harrison&Harrison having hardly any perfectly plano-parallel filters for sale. In recent decades this has been much improved, but not perfected.

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    Senior Member dchew's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by k-hawinkler View Post
    Quote:"I double-checked EXIF in Rawdigger - image stabilization was off."

    SteadyShot was really switched off, right? :-)
    At 4 AM I would forget that. :-(
    Yeah. I actually have Memory Dial 2 programmed for a tripod, and stabilization is set off in that mode, and I did check the EXIF data. Cuz yeah I would have forgotten that too!

    Quote Originally Posted by Annna T View Post
    I have had the same kind of double startrails with the A7r. I think it is a camera/sensor movement. It is very short, but strong (think a jump), which would explain why there are no zigzag to see. IMO, the 2 sec. shutter delay isn't enough to prevent motion. Using a remote (either the remote app on the iPad, or the cable remote), took care of the problem for me.
    Thanks Anna,
    I suppose that is possible, but I don't understand why it doesn't appear in the 35mm shots. I will test a longer delay when I get back and take some star photos!

    Quote Originally Posted by jlm View Post
    so the length of the star trace is rotation of the earth during the exposure, and the double trace, roughly perpendicular to that, is the issue?


    jm

    John,
    Actually parallel, but I think that is what you meant, so yes.

    Quote Originally Posted by henningw View Post
    I would have guessed a filter issue. Did you use a filter?

    I've seen exactly this with a filter which had the front and back planes not perfectly parallel. This used to happen on filters from the 70's and earlier very frequently, with Tiffen and Harrison&Harrison having hardly any perfectly plano-parallel filters for sale. In recent decades this has been much improved, but not perfected.
    No filter. But I still wonder about a reflection between the lens and the sensor, especially since it does not look like it is in the 35mm shot, although the trails themselves are smaller because of the wider view so it is harder to see for sure.
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    Re: Strange double image a7rII w Leica APO 50

    Dave, One possibilty is the shiny M mount of the AA 50 being exposed to the sensor. The RF coupling in this lens isn't shiny but the sensor could still see the M mount if the adapter is not baffled properly. The Loxia has a good baffle.

    Check the rear of the adapter with the AA 50 mounted.

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    Senior Member dchew's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by Vivek View Post
    Dave, One possibilty is the shiny M mount of the AA 50 being exposed to the sensor. The RF coupling in this lens isn't shiny but the sensor could still see the M mount if the adapter is not baffled properly. The Loxia has a good baffle.

    Check the rear of the adapter with the AA 50 mounted.
    Good idea Vivek, it is a Novoflex adapter and there is definitely some silver surfaces showing through with the adapter mounted.

    Update:
    I am beginning to think either Vivek or mjm6 are correct. I've been concentrating on the right side of the image because there are fewer clouds on the right. But actually the few stars on the left side do not have the double image on the ISO 100 image (30 sec exposure).

    So I re-opened the ISO 3200 shot in Rawdigger and compared it to the ISO 100 shot. The ISO 3200 shot was 3.2 seconds so there are almost no trails. Sure enough there are double points on the left side, but the fainter point is down and to the right, instead of down and to the left like on the right side of the image. You can't see it on the left side of the ISO 100 shot because the star trails cover up the double image on that side. [If anyone followed that I will be amazed!]

    As near as I can tell, in the ISO 3200 shot there are double points in a radial pattern. Looks like next week is test week! I have the 55 FE at home and will do some direct comparisons.

    Off to bed here in Switzerland and flying back tomorrow.

    Dave
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    Re: Strange double image a7rII w Leica APO 50

    I have had something like you mention with the Leica T when taking images with some candle lights.
    My interpretation was that it could be an internal reflection between sensor and lens.
    I have only experienced it in one situation, so I dont worry too much about it.
    Does it happen more often in your case?
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    Re: Strange double image a7rII w Leica APO 50

    Just can't trust these cheap lenses....
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    Re: Strange double image a7rII w Leica APO 50

    I think you're simply seeing star trails. You were shooting with a high pixel density camera using a fairly long lens (50mm) with a fairly long exposure time (10 seconds) at a latitude of 45.8 degrees. Generally speaking, at that latitude, to be safe, your maximum exposure time to avoid star trails should be 500/focal length, or in your case here, right at 10 seconds. I do recall tho that that formula may be based on film, not digital sensors, and do know from experience that the higher the pixel density the shorter the exposure time at which star trails will be apparent. So in this case I really do think it's just a matter of exposure time showing star trails. It doesn't look like mountain ridges show the effect, which I think bolsters my attempt at a reasonable explanation :-)

    Cheers!

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    Senior Member dchew's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by Paratom View Post
    I have had something like you mention with the Leica T when taking images with some candle lights.
    My interpretation was that it could be an internal reflection between sensor and lens.
    I have only experienced it in one situation, so I dont worry too much about it.
    Does it happen more often in your case?
    This is the first and only time I've seen this, which is why I am so curious. I used the AA50 on my a7r for a year and never experienced this, but I do not take many night photos, and perhaps none before with any Sony A series. Next week when I get the chance to test it out, I will use both the a7r and the a7rII. My guess is I will see it in both.

    Thank you all for your help. Another example of how great this forum is!

    Dave
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    Re: Strange double image a7rII w Leica APO 50

    I have no idea what caused the double image. Just wanted to say, what a gorgeous image, Dave. So beautiful and well done.
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    Re: Strange double image a7rII w Leica APO 50

    Looks like a reflection somewhere to me. You wouldn't get the extended star pairs on a long exposure like that with movement unless it was rapid oscillation between two points.

    My first thought was IBIS on whilst on a tripod but you say it was off. Could it have been anything related to focus? Did you adjust focus to nail the stars in the later shots that didn't have the mirrored stars?
    Remember: adventure before dementia!

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    Re: Strange double image a7rII w Leica APO 50

    Graham,
    All 4 images shot with the AA50 have the mirrored stars, but I can't remember if I readjusted focus at all during the four shots. So if I didn't it could be related to focus. After all it was dark and I was sleepy.
    This is one case where an optical viewfinder might have been better. There was an awful lot of noise in the viewfinder if I remember correctly.

    The fact that it only exists with this lens makes me suspicious Vivek is correct. I just find it hard to believe the metal chrome base of the lens would reflect such nice lines. But I am certainly not an optics engineer!

    Dave

    Quote Originally Posted by GrahamWelland View Post
    Looks like a reflection somewhere to me. You wouldn't get the extended star pairs on a long exposure like that with movement unless it was rapid oscillation between two points.

    My first thought was IBIS on whilst on a tripod but you say it was off. Could it have been anything related to focus? Did you adjust focus to nail the stars in the later shots that didn't have the mirrored stars?
    How glorious a greeting the sun gives the mountains! - John Muir

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    Administrator, Instructor Guy Mancuso's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    We needed a disclaimer:

    Animals were harmed during the filming of this production. This is blessed by Mother Nature so please no whining and no law suits. LOL
    Last edited by Guy Mancuso; 5th September 2015 at 09:51.
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    Senior Member dchew's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by Guy Mancuso View Post
    We needed a disclaimer:

    Animals were harmed during the filming of this production. This is blessed by Mother Nature so please no whining and no law suits. LOL
    That is funny Guy, but was it supposed to be in another thread perhaps? Like maybe one with a praying mantis and a hummingbird?


    Dave
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by Amin View Post
    I have no idea what caused the double image. Just wanted to say, what a gorgeous image, Dave. So beautiful and well done.
    Thank you Amin,
    As usual with my mini adventures, the "be there" part was the real joy. To get to Refuge Du Couvercle you have to first climb down some ladders and cross a glacier. Then you are met with this:



    Yeah that is straight up, or maybe even a bit overhanging for about 100 meters.

    And that's just the beginning! You just keep telling yourself it is no different than climbing a little ladder at home to clean the eaves.


    Dave
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    Administrator, Instructor Guy Mancuso's Avatar
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    Re: Strange double image a7rII w Leica APO 50

    Quote Originally Posted by dchew View Post
    That is funny Guy, but was it supposed to be in another thread perhaps? Like maybe one with a praying mantis and a hummingbird?


    Dave
    Bloody Mary kicked in. Lol
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