Beware The Invisible Beast That Lurks

If you are the owner of a Siamese cat you will know exactly what I mean…All the rest should be aware of dangers present in the simple UV filter.

These days we are told that the digital sensors of our cameras are not unduly affected by UV rays – nowhere near as much as the films we used to use. We need not put ” skylight ” filters on when shooting colour – at most, all we need is a clear glass filter to physically protect the front element of the lens from dust and dog noses.

But we have all been so long accustomed to that UV filter that it goes on all the time. In the studio today I found out just what that habit may have been costing me in the recent past.

The lens I was using was the widest that I have in my Fujifilm system – the 14 mm f:2.8 prime. It is a magnificent lens with a mechanical manual focus as well as a rapid autofocus. All metal too. I use it for interiors, large groups, and wide tabletop images. Never been unhappy with it at all…until I started to plan today’s tiny town shots. Luckily I looked carefully before shooting…

The lens was being used close-up to the edge of the set. I wanted to get the most depth of field so I planned to use the smallest aperture; f:22. All set, I tried the stop-down with the first pressure on the shutter button, but was annoyed to see that I had picked up a dozen spots on the sensor. So many more, in fact, than I normally get, that I wondered if the camera was on the fritz.

Then I remembered the time when I was using a UV filter in front of a zoom lens with a strong flash. I did not have sensor spots then…just white blobs everywhere in the image. The filter was holding dust at a point in the light path where it could catch the flashback.

And so it proved with the dark spots. Not on the sensor this time, but on that darned filter. As I was indoors I could afford to take it off and all the trouble vanished. I’ll give it a good clean, but even so will put it aside unless the lens is being used in the very worst conditions.


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