The Affect?

SCHNOOBS · Jan 8, 2008

I would imagine that two(2) R2 filters on one lens shooting with B&W ISO100 film, normal day, would it intensify the sky even more almost a dark blue to black tent... however my hypothesis could be wrong. has anyone every experimented with this?
input?

Garbz · Jan 9, 2008

Well firstly it's an effect

. Filters do not stack like this. Fortunately in the colour world (unlike in audio) filters are very close to ideal. That is if you hold a red filter to a colour spectrum chart you will see only the bright reds and potentially yellowish colours come through, the rest will be black. If they are not then you don't have a very good filter.

In the case of a poor filter stacking two would give the desired result at the expense of some light coming through.

However in the event of a perfect filter the result of stacking 2 filters would be the same as stacking one - the insertion loss of the second filter. So essentially since it's designed to filter out everything other than red and there's only the red light coming in, nothing is filtered.

If I understand correctly what you're trying to do is increase the effect even more. In order to do that you need to go further out into the spectrum. An R72 filter will raise the cutoff to 720nm (IR) but you need to check if your film is still sensitive to this kind of light. Obviously when you're approaching the limits of your film you hit the limits of your filter too.