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 the now discontinued 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 had great coating.

My guess is that the L37C designation meant absorption of UV Light under 370mu wavelength, and C means coated. If this hypothesis is correct, the L37C was closer to a Haze than to a typical UV filter of other brands. This could also explain why the L39C was discontinued earlier as the absorption of UV light between 370mu and 390mu was probably found either 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 series that have 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 layer 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 filter with your finger tip with one drop of light oil (even edible will do) is most of the times enough to prevent two filters from locking together.

Field 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 Pro 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

In the meantime, whatever filter you choose ... or not ...

Have a great time