Lens IR Status

Discussion in 'Black and White' started by slothead, May 5, 2013.

  1. slothead

    slothead Mu-43 All-Pro

    Aug 14, 2012
    Frederick, MD
    I have finally acquired what I need to use a number of my lenses for IR imaging and here are the results of my assessments. I shot with the following lenses to date and have found many of them create hotspots unfortunately. There is a chance that these results are compounded by the fact that my OM-D is unconverted, but I doubt it.

    Panny 20/1.7 - Good, balanced image
    Panny 14-140/4.0-5.8 - Creates hotspot dead center
    Oly 12/2.0 - Creates hotspot dead center
    Oly 45/1.7 - Creates a slight hospot in center and tendancy to flare (but could have been a shooting directional error)
    Oly 75/1.8 - Creates hotspot dead center
    Voigtlander 58/1.4 - major hotspot dead center

    So from my quick testing (using relatively inexpensive filters by the way) the only lens I have had what I interpret as success with is the Panny 20/1.7. I'll add more to this thread as I learn more about these lenses, filter quality and use on other cameras.

    Late addition and surprising revelation:
    Nikkor 28mm f/2.8 - Extremely balance, no hotspots or flaring



    I should comment that I need to reset my Custom White Balance since I would expect a much bluer sky after PP, although the fact that the camera has not been converted (and still has the IRC filter on it) may also be a factor. And in case you are wondering what color these flowers (in the unfocused foreground) are, here is an unfiltered visible light image.

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  2. F/Stop

    F/Stop Mu-43 Veteran

    Mar 9, 2013
    West Virginia
    Brian Y.
    thanks for your feedback..especially since this is something like i said before that i might want to dive into
  3. janneman

    janneman Mu-43 Veteran

    Dec 6, 2012
    Jan (John) Kusters
    Thank you! I did notice some hot spot in my first attempts too, but they are quite easy to correct in black & white (what is what I was going for). I am still waiting on more green on the trees here, and on good weather for further testing.
  4. STR

    STR Mu-43 Veteran

    May 16, 2013
    Panasonic 12-35 doesn't have a hot spot, at least I don't think it does since most of the shots I've taken with it don't have one. The 12-35 does have a tendency to flare right in the middle with an IR filter on. I should probably remember to bring the hood with me when going IR shooting.

    This is with a cheap-ish Fotga 850nm filter. I don't have a 720nm at the moment.

    Flare when pointed obliquely in the sun's direction.

    Nothing when pointed away.
  5. slothead

    slothead Mu-43 All-Pro

    Aug 14, 2012
    Frederick, MD
    I've avoided the 850nm filter recently. Seeing your images I may get it out again. I have had better luck with primes (I suspect because of generally fewer lens elements and groups), but not always. I've got a new prime I want to try (Nikkor 24/2.8 Ai-S) but haven't had a chance.
  6. RobWatson

    RobWatson Mu-43 Hall of Famer

    I've not tried IR (well NIR) photography but have done a fair amount of work imaging with NIR. Most of the materials used in typical lens construction are very efficient reflectors of NIR so hot spots abound and a very good lens hood is an absolute requirement. Even with a good hood the highly reflective surfaces of the lens interior will result in field flooding. The very best lenses used for NIR and IR are expertly baffled and have low reflective surface treatments specifically for NIR or IR wavelengths.

    If the lens optical elements have not be specifically designed or coated to manage NIR then flares and extra strong reflections will likely also be present if conditions are conducive.

    Not that any of this is particularly helpful but to set ones expectations appropriately does help moderate frustration. Clean up in post may not be quite so easy either - especially for field flooding and/or center hot spots. Sure the "bad" stuff can be attenuated a bit but sometimes it is only a matter of making it less the unacceptably annoying as opposed to "fixed".

    All in all I found working with NIR a tough nut to crack. Challenging, fun and frustrating. As an encouraging word note that a mediocre lens when properly coated for NIR can become a stellar performer! Even something as seemingly trivial as adding NIIR tuned anti-reflective coating on the sensor cover glass yields dramatic improvements in through-put and reflection reduction.
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