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Thread: Seeing Double - Seeking a Scientific Explanation

  1. #1
    Brownbear's Avatar
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    Seeing Double - Seeking a Scientific Explanation

    I stumbled across this photo of my attempt to photograph a rattle snake and I'm puzzled because the photo shows two snakes, and the fact of the matter is that there was only one rattle snake on the road.

    Does it look like two snakes because I moved the camera and it is just a fluky blur? Or a reflection? If it is a reflection I'm still puzzled because the only thing that I think could possibly create a reflection would be a parked car.

    Seeing Double - Seeking a Scientific Explanation

    Please excuse the quality of the photo. The real snake is the overexposed critter on the right and the reflection is on the left.

    If there is a photography technique to create two images of the same subject in one, I would like to know more about this.

    Thank you.
    Last edited by Brownbear; 15th April 2013 at 02:50 PM.

  2. #2

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    Re: Seeing Double - Seeking a Scientific Explanation

    Quote Originally Posted by Christina S View Post

    If there is a photography technique to create two images of the same subject in one, I would like to know more about this.

    Thank you.
    Yes Christina, there is. Your D80 probably has that function and you activated it without knowing. Go into the menu setup and see if you can find anything about double exposure. If your camera does not have that function you probably stumbled onto a technique I would also like to know more about.

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    rpcrowe's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Christina,
    Were you using a protective filter on your lens? This type of double image sometimes results from reflection on a protective filter, especially when most of the image area is dark and only a central spot is illumnated.

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    Brownbear's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Andre, No I don't have and function on my camera that says double exposure. The only similar setting I can find is for Multiple exposure which is for continuous shooting.. ie; 3 shots burst mode.. And EV steps and exposure compensation.

    Richard, For sure no because I don't have any filters for my camera.

    Thank you.

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    Re: Seeing Double - Seeking a Scientific Explanation

    Hi Christina,
    have a look at this http://www.learnmyshot.com might explain what's happened here.
    Regards
    John

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    Brownbear's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Thank you John, very interesting but I don't have this feature on my Nikon D90 (which is not listed in your link)... at least I can't find it anywhere. It is possible that I have this feature but I don't think so.

    The only other factor I can think of is that my friend was shining a flashlight on the snake?

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    Re: Seeing Double - Seeking a Scientific Explanation

    Hi Christina,
    I think you were right when you said Multiple exposure, have a look at the web page below.
    Did you move the camera slightly and did it fire twice.
    I'm only guessing but its interesting.

    http://jennychen.quazen.com/arts/pho...on-d90-camera/

  8. #8
    Brownbear's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Hi John,

    Well, that is mighty interesting! And also a bit embarrassing since until now I did not know that I had this feature on my camera, nor did I know that such a thing was possible.

    I suppose it is possible that I set my camera for what I thought was continuous burst mode, ie; 3 shots but then again I am not so sure I even knew about this back then as it was when I first bought the camera from a friend... I used a macro lens 105 mm because it allowed the most light. ie; aperture 2.8

    I was very nervous at the time, as it was the first time I've seen a rattlesnake. It is very likely that I moved the camera and also possible that I fired twice but I honestly can't remember. But my other photos of the snake only have one snake in them?

    Perhaps you have solved the mystery and I've learned something new about my camera and about multiple exposures.

    And here I was thinking that I'd discovered some magical photography technique!

    Thank you.

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    Re: Seeing Double - Seeking a Scientific Explanation

    Hi Christina,

    I have seen this before, in film as well, but very rarely.

    My theory is this ... Note the image is strongly divided into a very bright (over-exposed) and very dark region. Some lenses (the 105 mm Micro Nikkor, for example) have a rather large and almost flat back surface facing the sensor or film. It is my view that the very intense part of the image focused on the sensor can reflect from there onto that flat (ish) lens surface and appear as a weak ghost image elsewhere, especially in very dark parts of the image. With most lenses having a more curved back surface this ghost is highly out of focus so goes unnoticed, contributing only some flare.

    This ghost should, however, be reversed from left to right which challenges my theory. That could be explained, perhaps, by an additional reflection within the lens which dominates. I'm on thin ice here for that reason ;-) It would be helpful knowing what lens you used so I could investigate further.

    A perfect lens would never reflect any light off its elements but there is no such thing as perfection, advanced coatings notwithstanding.

    Best wishes,
    JH

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    Re: Seeing Double - Seeking a Scientific Explanation

    Christina,

    When trying to determine whether your camera has a particular capability, it's easiest to open the PDF of your camera manual and conduct a search, as an example, on "multiple" or "multiple exposure."

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    Brownbear's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Hi Garth,

    Your theory sounds great to me and I prefer it to the alternate explanation being that somehow I unknowingly set my camera to multiple exposure and performed this magical feat unwittingly.

    The lens used was indeed the AF Micro Nikkor 105 mm 1:2.8 my best lens..

    Thank you.


    Quote Originally Posted by JHzlwd View Post
    Hi Christina,

    I have seen this before, in film as well, but very rarely.

    My theory is this ... Note the image is strongly divided into a very bright (over-exposed) and very dark region. Some lenses (the 105 mm Micro Nikkor, for example) have a rather large and almost flat back surface facing the sensor or film. It is my view that the very intense part of the image focused on the sensor can reflect from there onto that flat (ish) lens surface and appear as a weak ghost image elsewhere, especially in very dark parts of the image. With most lenses having a more curved back surface this ghost is highly out of focus so goes unnoticed, contributing only some flare.

    This ghost should, however, be reversed from left to right which challenges my theory. That could be explained, perhaps, by an additional reflection within the lens which dominates. I'm on thin ice here for that reason ;-) It would be helpful knowing what lens you used so I could investigate further.

    A perfect lens would never reflect any light off its elements but there is no such thing as perfection, advanced coatings notwithstanding.

    Best wishes,
    JH

  12. #12
    Brownbear's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Thank you Mike. I have the PDF for my manual on my Desktop.. Next time around I will try this.

    Quote Originally Posted by Mike Buckley View Post
    Christina,

    When trying to determine whether your camera has a particular capability, it's easiest to open the PDF of your camera manual and conduct a search, as an example, on "multiple" or "multiple exposure."

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    Re: Seeing Double - Seeking a Scientific Explanation

    Was it quite a long exposure? I ask because I'm thinking of a bit of 'camera-shake' like: 1, 2, slightly move, 4, 5, 6, 7. In essence a movement so quick compared to the shutterspeed that the movement itself wasn't recorded but the start and end position were.

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    Re: Seeing Double - Seeking a Scientific Explanation

    If you look closely the faint snake is actually sharper (shorter exposure) than the 'main' one. Also the snake seems to have moved a bit - look at the orientation of the head and neck, and the shadows are different. (If I weren't a trusting soul, and this was a different forum, I'd suspect a bit of compositing via Photoshop.)

    Whatever, I don't think it's internal reflections. I'm going for two exposures, whether via Hero's method or multi-exposure.

    The different shadows have me wondering. Was Mr Rattle in the glare of the headlights for the whole time you were trying to shoot him, Christina?

    Tim

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    Re: Seeing Double - Seeking a Scientific Explanation

    Quote Originally Posted by Christina S View Post
    Andre, No I don't have and function on my camera that says double exposure. The only similar setting I can find is for Multiple exposure
    Hi Christina,

    Same thing spelt differently - Double is 2 and Multi is more than 2. I don't want to say it but - I have told you so.

    Not much difference between the D200 and D80, that is how I suspected that you activated that function.

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    Moderator GrumpyDiver's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Definitely two shots on the same frame. There would be other tell-tale signs in a reflection. If it were mirrored in an optical element, the image would be reversed (like looking in a mirror) and if it was not reversed, there would have to be a third instance of the snake.

    My film camera actually had a function where I could shoot multiple exposures on the same piece of film; i.e. I could cock the shutter without advancing the film.

  17. #17
    Brownbear's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Thank you to all.

    If I lighten up the shadows on the photo the position of the tail is different on the snake on the left hand side.

    I purchased the camera used so I suppose the multiple exposure could have been set by the previous owner without me knowing. I took these photos shortly after buying the camera so I don't think I would have gone into the shooting menu to change something I knew nothing about. This is the first time I've seen that setting in my camera and it is set to OFF... (And also to Gain up on?) However since I bought the camera I have reset my camera to default several times.

    Hero.... the exif data on my camera show

    iso 100 Exposure 3 Seconds Shutter Speed -1.58 ? Exposure Bias -.66 (you can tell that I knew what I was doing ) Aperture 3 Matrix metering

    Yes, the headlights from the parked car were on the entire time

    Hero, thank you for your trust.. Even though I've learned a lot about editing my skills are still pretty basic.. I could put two snakes in one photo but you would be able to tell that it had been done. I could email the original jpeg and raw photo if that helps.

    I guess because my camera has this function and everyone seems to think this is what happened, it is likely the case.

    Thank you

  18. #18
    Moderator GrumpyDiver's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Christina - it's hard to see it being anything else other than two different exposures on the same frame. All of the visual clues point to two different exposures; the lighting, the positioning, etc. It does look like the snake moved its tail between the two exposures. The lack of harsh shadows in the "secondary" snake makes me suspect that this was shot before the headlights were turned onto the snake.

  19. #19
    Brownbear's Avatar
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    Re: Seeing Double - Seeking a Scientific Explanation

    Hi Manfred,

    I know you know your stuff, so I guess we will have to go with the the strongest evidence and say that I must of somehow used multiple exposures. I also just noted that exposure comp on my other photos of the rattle snake is set at zero, which suggests a slip of the fingers to set the exp. comp at -1.67 on the above photo.

    My sincere apologies if I made anyone think that we had discovered a new photography technique. I thought it would be an amazing thing to be able to put two of one subject in one photo. And although I will never know how my camera was set to this, I'm glad that I posted because learned about multiple exposures and I will always have an entertaining story about how I learned about this feature.


    Thank you everyone.
    Quote Originally Posted by GrumpyDiver View Post
    Christina - it's hard to see it being anything else other than two different exposures on the same frame. All of the visual clues point to two different exposures; the lighting, the positioning, etc. It does look like the snake moved its tail between the two exposures. The lack of harsh shadows in the "secondary" snake makes me suspect that this was shot before the headlights were turned onto the snake.

  20. #20
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    Re: Seeing Double - Seeking a Scientific Explanation

    I have an Olympus 4/3rds that has the multiple exposure function and a Nikon that can do an overlay of two images. The multiple exposure function is fun but requires a bit of editing. You can also do the multiple exposure with a strobe.

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