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Filter Rings Without Filters.

Discussion in 'Accessories' started by Effuse, May 7, 2015.

  1. Effuse

    Effuse Mu-43 Regular

    25
    Aug 21, 2014
    BC, Canada
    I know this is really odd request but does anyone know if it's possible to buy just the filter rings threaded on each end? Without any actual filter or glass in them? I have an idea for a project and if could find these they would be perfect.
     
  2. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    The closest premade (without getting an actual filter and taking the glass out) I can think of would be a step up or step down ring, a reverse mount (normally used for macro) would be along the same lines.

    It wouldn't be hard to get tubing or round bar stock of the appropriate diameter and machine the threads if you have access to a lathe. The standard pitch for 37mm to 82mm is 0.75mm, 37mm and below were offered with a 0.5mm pitch (many 37mm filters intended for film lenses have this pitch as it was previously more common) and above 82mm generally go up to 1.0mm pitch.

    The cheapest filters I can think of would be a close up set (generally +1 +2 +4 and +10) for the diameter you desire, they're generally $10-20 on ebay for a set of four.
     
  3. Petrochemist

    Petrochemist Mu-43 Top Veteran

    651
    Mar 21, 2013
    N Essex, UK
    Mike
    I've investigated this breifly & decided the best option was removing filters from old threads. You can probably get some used filters to strip the glass from very cheaply much cheaper than the bar stock for cutting new ones.
    The type of filter doesn't matter if your removing it so old scratched ones that are only really relevant for film will be fine. IMO it's about the best use for most of the UV filters you see!
     
  4. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    In testing I've found most UV filters from the film era don't even filter UV, many of the colored filters for B+W only filter via virtue of fluorescence (that is to say that they glow when they absorb UV light hitting them).
     
  5. Petrochemist

    Petrochemist Mu-43 Top Veteran

    651
    Mar 21, 2013
    N Essex, UK
    Mike
    That throws rather a lot of doubt on your testing - they dont block all UV but they do reduce it significantly.

    I didn't keep the UV data on those I ran being more interested in the NIR region, I do have some data on old coloured filters:
    My old film era Cokin polarising filter blocks 75% of light at 350nm and all of it at 300nm compared to 50-60% in the visible. All the various coloured filters I've measured transmit less than 1% at 350nm with the Cokin Blue A020 giving the best transmission at 0.7%
    My testing has been carried out on a research grade UV-visible spectrometer, which I'm lucky enough to have available at work.

    Glass will typically absorb quite a bit of UV, and digital sensors include a filter to block it as well, below 200nm even the air absorbs UV.
    Digital sensors even without the filter are not particularly sensitive to UV compared to visible, film on the other hand is more sensitive to UV than visible light which is why it used to be helpful to filter out the little bit that makes it through the lenses for film use.
     
    • Informative Informative x 1
  6. listers_nz

    listers_nz Mu-43 Veteran

    255
    Nov 22, 2013
    Christchurch, New Zealand
    Simon
    • Informative Informative x 1
  7. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    I agree, they reduce it significantly. However the method they do so is what concerned me about older colored filters - they fluoresce by absorbing the shortwave UV and retransmit it as longer wave. Try shining a 350-410nm UV light on an older yellow/red/yellow+green filter and in all likelihood it will glow orange and become opaque, I found this out because of a very bright day at the beach and later testing.
     
  8. Petrochemist

    Petrochemist Mu-43 Top Veteran

    651
    Mar 21, 2013
    N Essex, UK
    Mike
    Coloured filters are not intended to reduce UV, their job is to change the relative intensities of the colours. If you have a bright UV source present lots of other materials will fluoresce too white cloth will usually glow blue...
     
  9. GRID

    GRID Mu-43 All-Pro

    Jun 22, 2011
    Or you can buy som cheap ones, unscrew the ring that holds the filter and remove it.
     
  10. Effuse

    Effuse Mu-43 Regular

    25
    Aug 21, 2014
    BC, Canada
  11. Yelkrub

    Yelkrub Mu-43 Rookie

    21
    Apr 21, 2013
    Cheshire, U.K.
    Paul