View Single Post
Old Oct 27, 2002, 12:52 PM   #3
sever
Member
 
Join Date: Oct 2002
Posts: 58
Default 87c IR Filter

I'm not sure what you mean by "where are you sourcing stepping rings from". I don't have a Fuji wide angle lens--I went with some cheaper lenses, I have a 0.5x and a 2.0x by Crystal Vision. They're not the best lenses in the world, but they're servicable and they expand my optical zoom from 17.5mm - 420mm equivalent. In any case, they measure 62mm.

I've noticed that they'll both easily take one 62mm filter without vignetting--the problem is that I'm interested in putting more than one. For example, I'd like to shoot with both a polarizing and a UV filter during the day. I have these in 55mm that I can put between the extension tube and the lenses, but then I get severe vignetting. Less of a problem if I use two 62mm filters, but I was hoping to get 3 or 4 if I could step up to 67mm off the end of those lenses.

The 87c is pretty close to the darkest IR filter out there according to what I've read...check it out: http://www.cliffshade.com/dpfwiw/ima...er_spectra.gif. The 50% transmissivity point is right around 850_nm, which is pretty high compared to the others. From what I've been able the gather, from highest to lowest transmissivity in the CCD-detectable spectrum: 89b -> 88a -> 87 -> 87b -> 87c.

Apparently the Hoya series of IR filters are labelled for the 50% transmissivity point, making it very easy to understand which filter does what. The Hoya R72, for example, has 50%T at 720_nm. The Hoya R90 has a 50%T of 900_nm (making it darker than the 87c).

I guess I'd be looking to start out with the 89b or 88a, whichever's cheaper. Actually, I'd like to start with the 89b I think because I've heard you can get cool false colors because it actually allows the very low end of the visible red spectrum through...though I guess the skies won't be as moody or forboding for it. Another advantage with the lower 50%T filters, though, is that the focusing situation will be less of a problem, especially at higher f-stops.

I'm mostly planning on shooting with these kinds of filters in daylight or bright indoor tungsten, so I don't really foresee the need to step down to ISO 1600 or stop up all the way. I've heard with the Canon G1 PowerShot people actually hand hold in bright daylight with an 87--at fully open f-stop they're getting 1/250th. I'm hoping to get somewhere around there with the S602Z and the 89b.

sev
sever is offline   Reply With Quote