R3 filter

lmd91343 · 03-19-2006

I have a Leitz A36 filter marked R3 . It is deep red, nearly opaque. I want to use it for some B & W infrared landscapes and flowers.

What is the filter factor? Any hints on using it with Kodak HIE?

I tried it on my old Sony videocam. I have the model that was recalled for revealing too much behind synthetic clothes in IR/nite mode. With this filter, it does what they said! Don't worry, it was only a test - OF MY WIFE. It will never be aimed at women wearing synthetic cloth. I am surprised that these things are not being wielded by scores of high school and college age boys at the beach.

Thanks,

kvanderlaag · 03-19-2006

That is just downright weird.

And creepy.

laptoprob · 03-19-2006

3x would be 3 stops. 8x longer exposure plus maybe a little more to compensate for specific film sensitivity. Try and be amazed, I guess.

edit: you can just measure through the filter and know for sure!

lmd91343 · 03-20-2006

Rob,

I measured with my Luna Pro. It is 3 1/3 stops. Good catch!

However, My Leitz 36A yellow filter's number designation (0,1,2,3) does not match their filter factor (1/3,2/3,1,1).

How does the designation system work? Is there a paper or web site somewhere?

Quote:

Originally Posted by laptoprob

3x would be 3 stops. 8x longer exposure plus maybe a little more to compensate for specific film sensitivity. Try and be amazed, I guess.
you can just measure through the filter and know for sure!

Thanks,

laptoprob · 03-20-2006

Measurement is Knowledge.
All other figures are approx. The value changes with light conditions too. That is why I used my CLE for BW filtering work in the first place. But a screwmount Leica is soooo cute!
This reminds me to go measuring my filters as well. Maybe the rule of thumb of my medium yellow, orange and red as 1, 2 and 3 stops has to be evaluated.
I have a few lighter yellows as well, but a little overexposure isn't bad.

VictorM. · 03-20-2006

Leitz simply numbered their filters, with the lower numbers indicating lighter shades of the same colour. The dark red, #3, had a filter factor of 15, with infrared film, in the early fifties. Of course modern films, infrared or not, will have different filter factors because their colour sensitivity is different. Also, some filters fade with age, again changing the filter factor. The only way to be sure is to shoot a test.

John Shriver · 03-20-2006

The dark red filter is listed as having a filter factor of 20 in the 1937 Leica III instruction booklet part III. Well, for Agfa R-Film, which looks like it must have been their infrared film. Only film they gave a factor for with that filter. Looks to have a cutoff wavelength of about 695 millimicrons.

VictorM. · 03-20-2006

The site is so slow, I didn't think I posted that reply.