[UV] Effects of calibrating a lens for UV use

Discussion in 'Night, InfraRed, and UltraViolet Photography' started by kds315, Apr 11, 2007.

  1. kds315

    kds315

    486
    May 30, 2006
    Dr Klaus Schmitt
    I have mentioned earlier that I made some tests after calibrating lenses for UV. This procedure has been done with candidates which showed satisfactory UV transmission. Here n6w some results. Reference lenses are the Nikon UV Nikkor 105mm and the Coastal Optics Micro Apo 105mm. Images cropped/scaled for comparison.

    Nikon D70 + 2" UG11xx shot at f11 ISO200 UV: 2" Nikon+Coastal, 4" 135mm lens (ca. -1.5..2EV as compared to the Nikon/Coastal); VIS: 1/125s

    1. UV Nikkor VIS
    76343715.
    2. 135mm calibrated lens VIS
    76340969.
    3) Coastal Optics VIS
    76342507.
    4. UV Nikkor UV
    76343716.
    5. 135mm calibrated lens UV
    76340971.
    6. Coastal Optics UV
    76342508.
    7. UV Nikkor Differential
    76343717.
    8. 135mm calibrated lens Differential
    76340973.
    9. Coastal Optics Differential
    View attachment 90005
    10. UV Nikkor detail Differential
    76351598.
    11. 135mm lens detail Differential
    76351597.
    12. Coastal Optics detail Differential
    76351599.
    13. UV Nikkor detail UV in bw
    76627013.
    14. 135mm lens detail UV in bw
    76627011.
    15. Coastal Optics detail UV in bw
    76627012.

    I will withold my personal comments for now and would like the group to comment on the results.


    Visual Reference Calibration: Macro
    76668013.
    Before UV Calibration: Macro
    76668014.
    After UV Calibration: Macro
    76668017.


    Klaus
     
  2. kds315

    kds315

    486
    May 30, 2006
    Dr Klaus Schmitt
    Some less technical results using this calibrated lens (Aubrieta deltoidea), diameter of flower ca. 10mm/ 0.5":

    76700267.

    76700268.

    Details (100% crop):

    76700442.

    76700443.

    Cheers, Klaus
     
  3. JoeG

    JoeG

    469
    Nov 2, 2006
    Tyrol, Austria
    It seems worth the effort to calibrate the lens :)

    I suppose that there is the same post processing on all UV shots:

    from the UV shots "out of cam" (?) (nr. 4 5 6) I like the Coastal Optics most closely followed by the Nikkor and then the 135mm lens, which has a much more reddish colour sheme (which is less usefull for post processing).

    from the UV differential images the Nikkor and the Coastal Optics image look the same, but the crops show that the Coastal Optics lens seems to have more contrast and it looks a bit sharper too.
    But it is very interessting that the 135mm lens is more likely to show the refelection of the roof in the window!

    the flower is nice in UV! The little spines seem to reflect UV quite good.

    greetings
     
  4. kds315

    kds315

    486
    May 30, 2006
    Dr Klaus Schmitt
    Joe,

    Same postprocessing applied. The UV shots (4, 5, 6) were auto whitebalanced only. I cannot follow your comment on the different colors since it does not correspond to my experience. Mainly I would guess, it is the outcome of the different wavelengths the lenses transmit. The 135mm lens does only 340nm with substantial fall off after 350nm, whereas the others are quite flat beyond 300nm.

    The differentials have to be interpreted very carefully, since the embossed 3D effect simulates sharpness where it is not but shows deviations in focal lengths (UV to VIS) i.e. focus shift mainly. Sharpness and contrast should be judged on the UV pics (color or bw) ONLY.

    This is the computed relative transmission of that 135mm lens (w/o coating effects):

    76852436.

    This is the result of the spectrophotometric test with that 135mm lens plus attached 2" UG11xx filter.
    Peak transmission is at about 370nm with some 43%, useful range 335nm ... 400nm. [pls keep in mind
    that my older spectrophotometer hasn't been clibrated for a while, so take these results more indicative]

    77360110.


    Klaus
     
    Last edited by a moderator: Apr 18, 2007
  5. mcdicky

    mcdicky

    42
    Mar 10, 2007
    Vancouver
    thanks for sharing
     
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