On Jun 21, 2005, at 10:05 AM, David Oswald wrote:
Ok, I'll bite. What problems do UV filters cause (assuming a
decent quality multicoated type)? There's the obvious: An extra
couple of glass surfaces which could themselves contribute to
flare, but is there anything else?
UV filters can cause problems with AF focusing, corner/edge
sharpness, etc. They tend to increase flare and reduce resolution as
well, even good ones.
Here's a very recent thread on DPReview that showed serious degrading
of the FA28-105/3.2-4.5 lens performance when using a Hoya HMC UV
filter:
http://forums.dpreview.com/forums/read.asp?
forum=1036&message=13954325
Prior to 20-some years ago, I was using UV and Skylight filters as
'protection' on all my lenses. One day I took a UV filter off for
cleaning and forgot to put it back with my Nikkor 35mm f/2 lens ...
My results that day were shockingly better than I recalled from using
that lens, so I did some testing. In every case, removing the filters
from my lenses improved their flare resistance and resolution,
sometimes only a small amount and sometimes by a substantial amount.
I stopped using UV filters for protection at that point and have only
used one in extreme conditions a couple of times since. (I was
already always using a rigid lens hood and continue to do so today.)
A side effect I noticed having removed all my filters is that my
lenses actually required less cleaning. Most of what I see now is
that they need an occasional dusting with a hand-bulb blower to stay
completely clean. With the filters, a thin film would build up
between the filter and the front surface of the lens about every
three-four weeks, requiring removal and cleaning of both glass surfaces.
Since both modern films and digital sensors are relatively
insensitive to UV light and don't need the filtration, a UV filter
for protection is only warranted when you're going to be shooting in
conditions of flying dirt or water. In such situations, the
degradation in optical performance is less significant anyway and
protecting the lens becomes a true need, not just a security blanket
to drop another buck or ten into a dealer's pocket.
In summary:
- Always use a rigid lens hood ... it helps protect the lens and
reduce flare.
- Always use a caps when you're not using a lens.
- Don't bother with filters unless you need to filter light, and then
use good filters with antireflective coatings.
Godfrey
