Filter Question: UV-2A vs. UV-17

[chrisreddy]

Hi,

I was wondering if anyone could shed some light on the relative benefits of choosing one of the above filters over the other. I know that both Haze 2 and Haze 17 block 100% of UV light, but what is the distinction that merits a seperate designation??

I'm using a Canon 40D with the 17-85 and I'm a long time user of the D30 (!) with the great 17-40L. I've had my 40D for about a year and still haven't bought a filter for the 17-85!

Thanks in advance!

p.s. It's great to be back on these forums. I was practically addicted from 2003-2005 so I had to ween myself off. Great community.

[TCav]

From Tiffen's own website for UV-17 filters:

"Absorbs slightly less UV light than Haze 2A"

From Tiffen's own website for Haze 2A filters:

"Absorbs virtually all UV light"
"Reduces haze more than Haze-1"

UV light is any light with a wavelength of 400nm or smaller.

Filters aren't perfect. A UV filter can't, for instance, block all light with a wavelength of 399nm and pass all light with a wavelength of 401nm. A UV filter will cut into violet light to some degree, and the stronger the UV filter, the more violet light it will block, in addition to the UV light it blocks. Weaker UF filters will pass more UV light so as to not block as much violet light.