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Thread: Can you explain this?

  1. #1
    WJT's Avatar
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    Can you explain this?

    I asked my wife to take some silhouettes of my on and I yesterday and she took them out of focus so we ended up with some abstract pictures, but this one has a reflection which sits out on its own and I haven't any idea how this happened. Anyone?
    Can you explain this?

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    Moderator GrumpyDiver's Avatar
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    Re: Can you explain this?

    My guess would be reflection off an element in the optical path, like a filter or lens element. Lens flare with flair...

    The part I can't quite figure out is what is causing the inversion in the image. That whould tend to suggest two reflections, including one off a concave lens element.
    Last edited by GrumpyDiver; 12th October 2012 at 02:52 PM. Reason: Duh - wrote convex and meant concave

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    Re: Can you explain this?

    Quote Originally Posted by GrumpyDiver View Post
    My guess would be reflection off an element in the optical path, like a filter or lens element. Lens flare with flair...

    The part I can't quite figure out is what is causing the inversion in the image. That whould tend to suggest two reflections, including one off a convex lens element.
    Thanks Manfred, it appears to be a perfect shadow from the sun itself but has been caught upside down. Does this mean that a shadow has ben cast on the lens which has turned upside down as it passes through to the sensor and caused flare on one of the internal glass filters?

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    Moderator GrumpyDiver's Avatar
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    Re: Can you explain this?

    Wayne - If you look at the image, it is not a shadow, but just a dimmer version of your initial the silhouttte against the sun, but inverted. Take a look at yourself using the inside of a metal spoon. You should see an inverted image of you. This means that there has to be a concave lens element that comes into play, rather than a surface that is flat or convex. Concave elements do occur in internal elements, so the only way that comes to mind is that is that there was some internal refection off a lens element, that then reflected off a concave portion of a lens element to invert the reflection and was finally caught on your sensor.

    I made a mistake in my initial response and wrote convex, rather than concave.

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    Re: Can you explain this?

    The image is reversed few times while traveling through the lens elements.

    The reflection has a point symmetry that of the center of the image (:=the center of the lens) and it's not a flare so it's a lens thing.

    You used however a high quality lens (it's the 70-200 f/2.8L ?) so it's weird you got this. Please tell me you don't use a cheap UV filter with beauty?

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    Re: Can you explain this?

    Nice image BTW!

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    Re: Can you explain this?

    Have you cropped this slightly?
    AFAIK, the reflection should pass through the centre of axis of the lens.
    GrahamH

    Can you explain this?

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    Re: Can you explain this?

    All explanations are way over my head, but I think the picture is very cool!

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    Re: Can you explain this?

    I believe it may be a reflection from the sensor itself, inverted by having been reflected back by one of the lens elements.
    I have found this problem when using bellows, as has another CiC member. It is a fault well known to designers of digital camera accessories such as polarizing filters. Hoya's Pro1 Digital polarizers, for example, have a coating on the reverse surface of the glass to attenuate this kind of unwanted internal reflection.

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    Re: Can you explain this?

    Whatever the true cause is, it's a classic result of reflections from a UV filter. Look at the shots on the following page...

    http://www.flickr.com/groups/canon_5...7603907741669/

    Did you have a UV or any other filter on the lens?

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    WJT's Avatar
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    Re: Can you explain this?

    Quote Originally Posted by MilT0s View Post
    The image is reversed few times while traveling through the lens elements.

    The reflection has a point symmetry that of the center of the image (:=the center of the lens) and it's not a flare so it's a lens thing.

    You used however a high quality lens (it's the 70-200 f/2.8L ?) so it's weird you got this. Please tell me you don't use a cheap UV filter with beauty?
    Interesting Miltos, I am using a Kenko UV which I was told was a good one by an enthusiastic salesman. Did he see me coming?

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    Re: Can you explain this?

    Quote Originally Posted by MilT0s View Post
    Nice image BTW!
    The idea is good but the execution not so good. I will try again after giving a crash course to my wife, some of the others are abstract and really interesting.

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    Re: Can you explain this?

    Quote Originally Posted by GrahamH View Post
    Have you cropped this slightly?
    AFAIK, the reflection should pass through the centre of axis of the lens.
    GrahamH

    Can you explain this?
    Yes Graham, it is cropped.

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    Re: Can you explain this?

    Quote Originally Posted by Brocken View Post
    I believe it may be a reflection from the sensor itself, inverted by having been reflected back by one of the lens elements.
    I have found this problem when using bellows, as has another CiC member. It is a fault well known to designers of digital camera accessories such as polarizing filters. Hoya's Pro1 Digital polarizers, for example, have a coating on the reverse surface of the glass to attenuate this kind of unwanted internal reflection.
    Interesting, Christopher this sounds plausible. I think I will send it into Myth Busters.

  15. #15
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    Re: Can you explain this?

    Quote Originally Posted by Graystar View Post
    Whatever the true cause is, it's a classic result of reflections from a UV filter. Look at the shots on the following page...

    http://www.flickr.com/groups/canon_5...7603907741669/
    Thats very similar in that it is upside down also. Yes I had a UV Filter on the 70-200mm, F2.8. Thanks for posting that comparison as it looks like the winning explanation having a with and without image.

    Did you have a UV or any other filter on the lens?

  16. #16
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    Re: Can you explain this?

    Here's a few others which are out of focus but have some interesting abstract effects.
    1. Can you explain this?
    2.Can you explain this?

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    Re: Can you explain this?

    Quote Originally Posted by WJT View Post
    Interesting Miltos, I am using a Kenko UV which I was told was a good one by an enthusiastic salesman. Did he see me coming?
    Any filter should be removed when the light source is shining on it
    The UV filter has been called the salesman's bonus ... though advisable in dirty situations such as at the beach to protect the lens. I just advised my son to buy one before he goes to the Moab, except when the sun is shining on the lens when he should shade the lens with his hand ... but hardly advice when pointing directly at the sun as your shot

  18. #18
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    Re: Can you explain this?

    I am using a Kenko UV which I was told was a good one by an enthusiastic salesman. Did he see me coming?
    Asking about the use of filters can start a huge and predictable argument (although I think not on this forum). I'm going to try to avoid igniting that while giving you a few suggestions:

    1. Don't use any filters of any kind unless they are high-quality, multi-coated filters. I don't know if the Kenko is. I only have Hoya and Marumi at this point. (I only recently learned about the extra coating on the Pro--too late for this round of filters).

    2. Unless you absolutely need it, don't use filters when you have a light source in front of you. That is when you get reflections, flare, ghosting, etc.

    I'm one of those people who actually does use UV filters for protection if I am in environments where I have reason to worry (I've been doing this for over 40 years), and I have done a few tests that suggest that with good filters and good lighting behind you, the effect is minor. However, I always take them off in circumstances where lighting is in front of the camera.

  19. #19

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    Re: Can you explain this?

    Marumi are now using the sensor reflection problem as a selling point for their range of filters for the digital camera market - here, with diagrams: http://www.marumi-international.com/dhg/

  20. #20
    WJT's Avatar
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    Re: Can you explain this?

    Quote Originally Posted by jcuknz View Post
    Any filter should be removed when the light source is shining on it
    The UV filter has been called the salesman's bonus ... though advisable in dirty situations such as at the beach to protect the lens. I just advised my son to buy one before he goes to the Moab, except when the sun is shining on the lens when he should shade the lens with his hand ... but hardly advice when pointing directly at the sun as your shot
    Good advice, I did stop using them myself for a while as you can get most effects that you want in PP these days and I prefer to get a pure shot in the first instance. I was however concerned about damage to the glass.

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