Infrared photography Question

Discussion in 'Digital Discussion & Q&A' started by Ebag17, May 15, 2009.

  1. Ebag17

    Ebag17 TPF Noob!

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    I got my IR filter and took a few shots in my backyard. I'm trying to figure out what all these spots are. Are they hot spots? They were taken with a Canon 40D and Sigma 10-20mm

    Here are the photos...

    Flickr: Ebag17's Photostream

    Thanks for your time and help.

    -G
     
  2. Josh66

    Josh66 Been spending a lot of time on here!

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    That's not hot spots. A hot spot will be a large spot in the center of the frame, the more you stop down the bigger it will get. Not all lenses will produce them.

    Were you shooting into the sun? Looks like lens flare, or maybe water droplets on your lens...?
     
  3. Ebag17

    Ebag17 TPF Noob!

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    Hmmmm. Thats what i thought at first. In those photos the sun was behind me and a lens hood. I made sure the filter and lens was clean. I went to a camera shop and they did'nt really have an explanation either, except that light could be gettng in between the filter and lens?
     
  4. Josh66

    Josh66 Been spending a lot of time on here!

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    Not really sure how that could happen, and if it did - it wouldn't be red (since it would be unfiltered).

    I really have no clue what that is... I've never seen it in any of my IR pictures, and it's definitely not a hot spot.

    I would bet that it's some kind of flare though.

    Just had an idea-

    Did you cover the viewfinder?

    Since this was likely a long exposure (5-10 sec?), I assume that you didn't have your eye to the viewfinder the whole time. If left uncovered (your camera probably came with a cover for it), light could enter through the viewfinder. Maybe that's what's causing this?

    edit
    But that light would be unfiltered too, so it still shouldn't be red...
     
  5. Dwig

    Dwig TPF Noob!

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    Not light through the VF because during the exposure the mirror is up sealing the mirror box. Light entering through the eyepiece can't get to the sensor during the exposure. Eyepiece covers and blinds are to prevent light getting into the VF through the eyepiece and influencing the meter prior to exposure.

    The spots are obiously bright, very out of focus, and in front of the IR filter as evidenced by their having a noticable hexagonal shape and the same color as the rest of the image. Given that no bright light sources are in the primary distant portion of the image they are most likely something very near the lens that is either emitting or reflecting substantial amounts of light (more than the rest of the scene). These could be water droplets or dust near the lens lit by some source (flash??) or possibly smoke particles (was the photographer smoking at the time??).
     
  6. Josh66

    Josh66 Been spending a lot of time on here!

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    Ah- Gotcha.
     
  7. Ebag17

    Ebag17 TPF Noob!

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    Nope. Don't smoke. Neither was there a flash. I have a UV filter between the lens and IR filter? I don't know if that could have any effect. Playing around with the white balance seems to help a little but, there's still obvious spots everywhere.

    Also when you said exposure time of 5-10 sec is that how long IR is suppost to be? those images where taken for 60sec?

    As pertaining to it being dust. The spots seem to be random. Would there not be a somewhat pattern to them if they where fixed spots of dust on the lens.

    The filter I'm using is a 77mm Tiffen 87 filter. Have you ever heard of any problems with these filters?
     
  8. Josh66

    Josh66 Been spending a lot of time on here!

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    That could be the problem. If not, it sure isn't helping.

    I would remove it when you have the IR filter on.

    If you're using it to block UV light, the IR filter is doing that.
    If you're using it for protection, the (much more expensive) IR filter is doing that now too since it's on top.

    I wouldn't move it to the top of the IR filter either. Just remove it, then put it back on when you're done if you like using it.
     
  9. Garbz

    Garbz No longer a newbie, moving up!

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    What IR filter is it? Is it a screw on filter or a plate type sitting in a Cokin holder.

    I say this because it looks like there may be light leeking into the side of the filter lighting up the dust specs on the lens. Now due to the long exposures these dust spots suddenly really matter.

    Remove the UV filter, Place the IR filter flush against the lens and maybe surround it in electrical tape. See if it still happens. If not maybe there's some problem in the filter.
     
  10. Josh66

    Josh66 Been spending a lot of time on here!

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    That's how long my exposures typically are, but that doesn't necessarily mean your's will be the same. There are too many variables for your settings and mine to match up.
     
  11. benhasajeep

    benhasajeep TPF Noob!

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    I think your getting reflection between your filters. The spots have moved and are a different size when you went from one scene to another. The light is bouncing around and creating the spots, they are octagnal shapes becasue of your aperture blades (reflections).

    I would take off the UV and use just the IR filter.
     
  12. Ebag17

    Ebag17 TPF Noob!

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    Alright I think I've got it figured out! Thanks all for your help

    -G
     

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