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Ultraviolet Hidden Markings, Are Very Good At Hiding?

Discussion in 'Black and White' started by YouVIart, Jun 29, 2014.

  1. YouVIart

    YouVIart Mu-43 Regular

    111
    Aug 17, 2013
    Kingdom Of Wessex
    Most of the time, ultraviolet shows different markings and colours. Daisies and Dandelions look different, and almost everything else.
    Bessell-U & BG38 filters, for once, seeing eye to eye.
     

    Attached Files:

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  2. kds315

    kds315 Mu-43 Regular

    149
    Apr 6, 2010
    Weinheim, Germany
    That Bessel Filter seems to leak, as the Dandelion clearly shows in UV....
     
  3. YouVIart

    YouVIart Mu-43 Regular

    111
    Aug 17, 2013
    Kingdom Of Wessex
    Yes, Yesterday, I did this little test, with my BG38 to the left side and in front of this bloom. Bottom two photos are with open aperture f/3.5, Time 18:30..ish.
     

    Attached Files:

  4. YouVIart

    YouVIart Mu-43 Regular

    111
    Aug 17, 2013
    Kingdom Of Wessex
    Bessell+BG Blue-bloom Bee-fest'.

    Today, in the glorious Kingdom Of Wessex, done a Bessell-U and Bessell-U+BG38 test. This blue bloom, looks the same in UV and visible light. Though, the Bessell-U does have a tiny violet leak.
     

    Attached Files:

  5. Petrochemist

    Petrochemist Mu-43 Top Veteran

    651
    Mar 21, 2013
    N Essex, UK
    Mike
  6. YouVIart

    YouVIart Mu-43 Regular

    111
    Aug 17, 2013
    Kingdom Of Wessex
    Novoflex Noflexar 1 : 3,5 / 35, a common lens for UV.
     
  7. YouVIart

    YouVIart Mu-43 Regular

    111
    Aug 17, 2013
    Kingdom Of Wessex
    B&W Bessell-U Vs BG38 Extremist Aperture Shoot-out.

    Bessell-U = Soft Focus; BG38 = Sharp Focus. There's a lot less light to shoot with, when UV-pass filters are used.
     

    Attached Files:

  8. kds315

    kds315 Mu-43 Regular

    149
    Apr 6, 2010
    Weinheim, Germany
    Nice examples, quite obvious that using a BG38 reduces the leak considerably.
     
  9. YouVIart

    YouVIart Mu-43 Regular

    111
    Aug 17, 2013
    Kingdom Of Wessex
    Cheers, there isn't much leakage, even a BG38 can deal with it. The evening atmosphere, was acting as a weak UV-block/IR-pass filter.
     
  10. kds315

    kds315 Mu-43 Regular

    149
    Apr 6, 2010
    Weinheim, Germany
    Of course this lens is not suitable for recoding UV."Scattering effect" of a lens? Are you joking in that IR thread, it's simply the glass absorption and the coating which causes transmission losses.
     
  11. Petrochemist

    Petrochemist Mu-43 Top Veteran

    651
    Mar 21, 2013
    N Essex, UK
    Mike
    No Joke, Klaus just badly worded.
    The lenses were not aligned with the spectrometer beam, so with wide angle lenses the beam will be bent more than for longer focal lengths. With many lenses this still means the light beam totally hits he spectrometer sensor, and gives good results.
    The Olympus 17mm has much smaller target and bends the beam significantly, 'scattering' the beam beyond the instruments sensor, giving transmission reading below what actually would be transmitted by the lens..
    I'd be very surprised if the 17mm lens doesn't actually transmit more than twice what I was able to measure in the visible part of the spectrum at least.

    Those measuring lens transmission commercially will have an optical bench to align the lens exactly with the light beam. I had to make do with propping it so as to be as near center as possible.
    Although the deflection of the light beam will vary with wavelength in most cases, I'd expect this to make fairly little difference to the relative transmissions.
     
  12. kds315

    kds315 Mu-43 Regular

    149
    Apr 6, 2010
    Weinheim, Germany
    It is even more complicated than that, took me a while to figure that out. A normal spectrometer just has a straight beam and lenses disperse that, especially wide angles. Really tricky to get those measured correctly, aligning the beam is just one aspect ;-)