how much is the Hoya R72?

Also can you use the polarizers instead of using ND filter for IR photo?

Hi Christopher,

I paid $53 (AU) for a Hoya R72, I use an ND8 and an ND4 together with the R72, I don't think a polarizer will make it dark enough.
Skippy (Australia)

Christopher Ng said:

Also can you use the polarizers instead of using ND filter for IR
photo?

Click to expand...

--



Everyone has a right to be stupid. Some just abuse the privilege. (Unknown)

I think the Hoya R72 usually runs $40-something in the US. (I bought mine for $40.46, if I remember right, from photofilter.net.)

As far as polarizers instead of an ND filter-- I agree with Skippy, I don't think that would block enough light. (But I'm just a beginner, so am just learning.) I've been using an ND 8 with my R72.

Melanie

I paid $27.99US for mine @ http://www.freestyle.biz

Christopher Ng said:

Also can you use the polarizers instead of using ND filter for IR
photo?

Click to expand...

--
Jamie Haggett
Sony DSC-S85
http://www.pbase.com/jhaggett/
Edmonton, Alberta Canada

mlynn said:

I think the Hoya R72 usually runs $40-something in the US. (I
bought mine for $40.46, if I remember right, from photofilter.net.)

As far as polarizers instead of an ND filter-- I agree with Skippy,
I don't think that would block enough light. (But I'm just a
beginner, so am just learning.) I've been using an ND 8 with my
R72.

Melanie

Click to expand...

Note, he typed "polarizerS" plural, I think he implied crossed-polarizers, 2 of them. I've not played with IR photography with this camera yet (one can afford just so many add-ons when starting out), But I have used crossed-polarizers as a variable neutral density filter. It's the best solution for wanting to dial-in just the right amount of slow-shutter motion effect in water and other things of that nature.

So, if he did mean crossed-polarizerS, plural: Then 2 of them, NOT crossed at 90 degrees will increase my exposure from 1/1000th of a second to 1/125th of a second, (which is what change in aperture?, someone help me with the math here, I've been up late... , it's 3 f/stops difference.

When they are crossed at 90 degrees to extinguish the light, it will increase the exposure from 1/1000th to 5 (whole) seconds, which is what again in f/stops??? (gawd I hate doing math when I've been up late, specially fractions involving the reciprocal of decimals mixed up with the power of 2 ... uh ... a little over 12 f/stops difference. (What value would that be for a ND filter number? I forget how that works, I never used one, only crossed-polarizers.)

I'd say he could probably use 2 crossed-polarizers to accomplish IR photography insetead of an ND filter. It's what I'll be trying when I get an IR filter.

Does anyone have real-life experience with this that could confirm this?

The only drawback I forsee will be watching for reflections and highlights that you want to keep that TWO polarizers at different angles will want to wipe out from 2 angles of incident light now, not just one plane of reflection.