In degree of absorption
of UV light under 400mu wavelengths -the industry standard-
first are the UV filters, with "basic" reduction that varies
across brands; then the Skylight (about 50%); then Haze
1 (about 70%), then Haze 2 (up to about 99.7%).
In order to reduce
the flare that might be induced by additional glass surfaces
on top of a lens, and also to suppress light reflected out,
"bounced" away on a filter surface, it is important to insist
on multi-coated filters, like the Nikon and Hoya S-HMC and
Pro 1 series. Otherwise you are inviting flare to come into
the scene.
So all of these
filters absorb/transmit ultraviolet light rays in varying
degrees and render cleaner, sharper images with less haze.
And therefore it was highly recommended to leave a UV, Haze
or Skylight filter on your camera lens at all times to protect
it from dust, moisture, scratches and breakage. If you have
small children around, all sort of foreign materials can
land on your lens front element. If you have been denied
the joys of children around, or will not encounter water,
dust, sand, then by all means go "naked".
In consequence,
before becoming aware of the improved characteristics of
modern color film, I bought Nikon L37C filters for all my
lenses, because they cut out UV light invisible to the naked
eye, with no effect on visible light and have great coating.
My guess is that
the L37C designation means absorption of UV Light
under 370mu wavelength, and C means coated.
If this hypothesis is correct, the L37C is closer to a Haze
than to a typical UV filter of other brands. This could
also explain why the L39C was discontinued as the absorption
of UV light between 370mu and 390mu was probably found either
now unnecessary or the skies unpleasantly devoid of all
blue.
However and again, today, when
most modern digital camera sensors and color films -although
not all- are insensitive the UV light,
I have replaced all L37C filters with Nikon A2
ones or Hoya HMC 81A and looking into the
Hoya Pro 1 series that has the S-HMC coating. These,
while continuing to cut some UV light if necessary, add
a usually pleasing warming tone to images and don't induce
flare.
NIKON AND HOYA
In
1996 Hoya introduced its line of Super Multi-Coated S-HMC
filters. Consisting of the Skylight 1B, UV (0), ND 2X, ND4X,
and a low profile circular polarizer. This line of filters
has a 5+1 layering system on each side of the glass: 5 layers
of anti-reflective coating and a transparent easy-clean
top coat, making the filters 12 layers ones. This reduces
light reflections off the filter surface to an average of
just 0.3%. This seems to be the lowest reflective rate on
the market from any filter manufacturer, except Nikon.
B+W
and Heliopan filters, among others, look most attractive
because its use of German Schott glass and their brass non-binding
rings; but, if binding is a concern, the rubbing on the
threads of a finger tip with one drop of light oil (edible
will do) is most of the times enough to prevent two filters
from locking together.
Research
has also confirmed that B+W and Heliopan filters on the
stores shelves have less layers of multi-coating than the
Nikon and recommended Hoya series, both also made from glass
bars.
As soon as feasible I will retreat
into the mountains or the sea and will try to remember
to illustrate the effects of
- Not using filters
(like in the image at right)
- Using non-multicoated
filters, not-so-multi-coated ones and
- Using the filters as recommended
above
- With a digital camera and on film |
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In the meantime,
whatever filter you choose ... or not ...
Have a great time 
