Re: IR Filter

[Willem-Jan Markerink <w.j.markerink@xxxxx>]

On 18 Jul 96 at 16:31, Russell J Rosener wrote:

> I just recently purchased a Hoya R72 infra red filter. I thought it was
> able to pass some visible light for focusing, but it seems virtually
> opaque to visible light. Is there a Hoya filter which is even more opaque?
> Would that be the R70? There no useful information on the filter factor
> packed with this thing. What would be a filter factor guideline? 
> Has anyone used this filter with Konica IR?

Mmm....are you saying Hoya R72 is too opaque or too transmissive?
According to all my lists, brochures and tables, it equals #89B, and 
IMO this is the darkest visible color usable in front of a lens. But still 
very transmissive.
Hoya did have an R90 filter, but according to the Dutch distributor, 
it is no longer made (can anyone confirm this for other parts of the 
world??). But it is still in their latest glossy brochure, including 
an UV-short pass filter (also no longer made apparently). The text of 
R90 says that it still has a rest transmission in the visible, 
although the transmission plot looks like a very dark opaque 87A filter. 

 
--
Bye,

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<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]