Simple way to test UV Filter quality

Discussion in 'Accessories' started by shineofleo, Jul 6, 2010.

  1. I just bought some off-brand UV filter, and it looks quite good. The ring is well made, the glass seems fine with naked eyes, and so-called Multi-Coating looks well applied.
    I know the easy way to test it is put it on a lens and take some picture, compare with no filter and other filter pictures. I am wondering is there any alternative method to test the quality of UV filters? Can it be done at home instead of a professional lab?
    This can be useful because it is always good news for us to have a good filter at a low price.
  2. Go to:
    Search for my name, "Tom Mann", on that page. This should bring you to my first post in that thread (Jan 8, 2010 at 2:32 PM EST). In that post, I describe how to quickly check how much a particular filter degrades the performance of a specific lens ( a given zoom FL, at a given f-number, at a given off-axis angle, at a given degree of over-exposure, yada, yada).
    The test uses nothing more than a single off-camera strobe (on manual) pointed back at the camera (also on manual) in a dark room. I give an example of such a test done on a Nikon 28-70/2.8, with and without a UV filter.
    Above, I mentioned several different parameters that all affect flare and ghosting, both with and without the added filter. In principle, one should investigate many different combinations of FL, f/number, off-axis angle, etc. However, in practice, just a few important combinations of parameters will give you a good overview of that combination of hardware, eg, wide-open and f/11, zoomed all the way in and all the way out, and just one angle, say, with the light source 1/3rd the way out towards the most distant corner of the frame (at each zoom setting). The single most important factor is to keep the degree of overexposure constant, say, 5 stops. If it varies between tests, you will be comparing apples to oranges.
    Once you have done such tests on your own equipment, you'll be one of the few people with real data on the subject, and you can then safely ignore the religious wars that regularly break out between the "always use one" and "never use one" factions. :)
    Tom M.
  3. Thanks a lot Tom! That's really helpful. I will do some experiment like this to determine if the filter is good or not!

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