IR Filter ? (Not a "what should I buy" thread)...UV too

Discussion in 'Beyond the Basics' started by Josh66, May 4, 2009.

  1. Josh66

    Josh66 Been spending a lot of time on here!

    Joined:
    Oct 31, 2007
    Messages:
    14,604
    Likes Received:
    1,236
    Location:
    Cedar Hill, Texas
    Can others edit my Photos:
    Photos NOT OK to edit
    OK, I have two B+W IR filters. The 092 (89B) and the 093 (87C).

    The 093 filter is supposed to block the entire visible spectrum.

    So - why can I see through it?

    Sometimes it's hard to tell these filters apart with a quick glance, so I hold them up to some light. The 092 filter does not block all visible light, so you can see through it OK in bright light. The 093 filter should be blocking all visible light, so it still looks black; but - I can see the sun through it.

    If it's blocking all visible light, how is it that the sun is visible to the eye through it?

    If it really did block all visible light I should not be able to see anything through it, including the sun, right?

    And I know about the dangers of looking at the sun, I'm just talking about a brief glance through a very dark filter here.



    One more question, just so I don't have to start a new thread...

    The UV filters (not that kind) are looking pretty interesting too. I'm talking about the filters that block everything except for UV light. These.

    Does anybody know what the sensitivity of the 350D (or any other body) is to UV light?

    The glass in my lenses will absorb some of the light too (I think I remember reading that quartz lenses are best for this...$$$$), right?

    I guess what I'm asking is, is it even worth trying?
     
  2. Garbz

    Garbz No longer a newbie, moving up!

    Joined:
    Oct 26, 2003
    Messages:
    9,713
    Likes Received:
    203
    Location:
    Brisbane, Australia
    Can others edit my Photos:
    Photos NOT OK to edit
    No filters are perfect. The 093 filter has an 830nm cutoff which is well into the infrared but the sun is such a bright source that would be visible since a couple of percent of the light is still visible at around 780nm and below. That said it also won't have a 100% perfect stop band.

    All your assumptions are correct, except the one about looking at the sun. The filter is not dark, it is outright dangerous. All the bright light that causes heat (IR) passes through the filter. You put the filter to your eye and your pupils dilate because you think it is dark letting more light in. This lovely warming light then gets focused onto your retina. All it takes is a few seconds of this kind of exposure to raise the temperature enough to permanently blind you! IR is a very different beast than UV light, I suggest you don't do this again.

    Also digital camera sensors are next to not reactive to UV light at all. Same as IR, except the IR is a result of a filter that can be removed. Also lenses block a lot of UV light naturally, often enough to make this kind of photography impossible with a digital camera. Not sure of Canons equivalent but for UV photography you need something like a Medical-Nikkor or UV-Nikkor lens to get going, whereas nearly any lens will do for IR photography.
     
  3. m2v

    m2v TPF Noob!

    Joined:
    Feb 12, 2009
    Messages:
    83
    Likes Received:
    0
    Can others edit my Photos:
    Photos OK to edit
    How does a UV photo look like?
     
  4. Josh66

    Josh66 Been spending a lot of time on here!

    Joined:
    Oct 31, 2007
    Messages:
    14,604
    Likes Received:
    1,236
    Location:
    Cedar Hill, Texas
    Can others edit my Photos:
    Photos NOT OK to edit

Share This Page

Search tags for this page

ir filter for sun

,

ir filter for sun photos

,

ir filter sun

,

looking at sun through ir filter

,

sun photography ir filter

,

using ir lenses to look at the sun

,

will uv lenses filter ir also?