Wavelength cut off points for typical glass lenses?

Discussion in 'Miscellaneous Equipment' started by Athiril, Dec 23, 2010.

  1. Athiril

    Athiril Subscriber

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    I was wondering what the typical cut-off points of the spectrum are for typical lenses.

    (Specifically I own an uncoated Ektar lens, various primes of the 70s-80s such as Olympus OM lenses, Super Takumar etc, and some modern lenses like the Sigma 12-24mm).

    EG: Can a regular lens pass the 900nm-1200nm range of IR?
     
  2. Q.G.

    Q.G. Inactive

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    Yes. No problem.
    (You could start worrying when looking to record in the band well beyond 2000 nm)
    A bigger problem is finding something that records radiation in that band.
     
  3. michaelbsc

    michaelbsc Member

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    My question would be more how you focus an image duwn there.
     
  4. benjiboy

    benjiboy Subscriber

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    I let the lens manufacturers worry about questions like this.
     
  5. Christopher Walrath

    Christopher Walrath Member

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    Radiation will pass through a lens (and other forms of matter). And mentioned above, you just need to visually capture it.
     
  6. Q.G.

    Q.G. Inactive

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    That makes it sound, sort of, as if the question was flawed.
    Not all radiation passes through all forms of matter. Not all light will pass through (all) glass.
     
  7. Athiril

    Athiril Subscriber

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    Well I know apparently you need a gel lens to capture in the lower side of UV rather than just "near" UV.

    Anyway thanks Q.G. that should help.
     
  8. Photo Engineer

    Photo Engineer Subscriber

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    You can get surprisingly far into the "near" UV and that is why film manufacturers put a UV layer in many films. Ordinary glass lenses pass too much UV light. This is especially true with high altitude photography. The higher you go, the more UV radiation and the more you need UV filtration. Of course if you want 'far" UV, you need quartz lenses.

    PE
     
  9. pgomena

    pgomena Member

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    I had an assignment in photo school to make a photograph using UV light. Tri-X, special filter, and bingo!, a picture was made. I'm sure it was using very near-UV. The thick glass filter was a very dark violet color and nearly opaque to my eye in broad daylight.

    Peter Gomena
     
  10. Maris

    Maris Member

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    The nominal cut-off for glass is 340 nanometres. Deep violet at the limit of human eye sensitivity is supposed to be 400 nanometres but some people see slightly more, some less. Further down in the ultraviolet the next limit is 190 nanometres, the start of the vacuum ultraviolet, where air itself imposes a cutoff.