Testing UV lens filters

[John Jarosz]

This may be kind of a oddball question, so you've been warned.

Is it possible to compare the effectiveness of UV filters by measuring UV density on a UV densitometer? I have a xrite 316 and I was wondering if the density readings of the filter would correlate in any way to how well UV is attenuated by the filter. I imagine the UV wavelengths are important here and how wide a range the densitometer is set up to read.

Thanks

john

[Drew Wiley]

No. This is because different kinds of film have different sensitivies to UV. The negative effect of UV can be to mildly disturb sharpness or to degrade color balance a
bit. The effect on sharpness due to mild atmospheric pollutants is a secondary factor
to be taken into account. I own a variety of UV filters because I shoot more than one
kind of film. It's mostly a problem with distance shots at high altitude. And there's
no substitute for actual field testing.

[John Jarosz]

I thought it might be something like that.

It's mostly a problem with distance shots at high altitude

The above is exactly what I'll be facing. Has anyone posted any data on the UV sensitivity of different films? (like FP 4+ ?)

Thanks very much

[Drew Wiley]

No. This is because different kinds of film have different sensitivies to UV. The negative effect of UV can be to mildly disturb sharpness or to degrade color balance a
bit. The effect on sharpness due to mild atmospheric pollutants is a secondary factor
to be taken into account. I own a variety of UV filters because I shoot more than one
kind of film. It's mostly a problem with distance shots at high altitude. And there's
no substitute for actual field testing.

[Drew Wiley]

Ooops, sorry for the double post. With black and white films it's often a non-issue because we might use contrast filters. For example, a red filter is going to cut haze
as well as UV far more efficiently than any UV filter. For a more subtle use, a light yellow or yellow-green filter is adequate. But as far as actual sensitivity of respective
films is concerned, simply go to the mfg tech sheet for each and look at the spectrogram, and this will tell you have far into the UV the film "sees".