Re: WJ & light leakin Hoya's

[George L Smyth <glsmyth@xxxxxxxxxxxxxxxxx>]

On Tue, 7 Sep 1999, Cameron Shaw wrote:

> reply at end:
> 
> danzig@xxxxxxxxxxxxxx wrote:
> > 
> > > Or: not just to the level of being able to see the filament in a
> > > light bulb, but to the level of seeing the entire bulb as well as
> > > surrounding objects.
> > 
> > WJ is right about this (i tested me R72), I have your usual tungsten
> > lighting in the room, single bulb 60 W. And I COULD see the
> > tungsten lamp & a bit of the area surrounding the lamp.
> > 
> > I imagine the leak to be worse with 500W tungsten studio lighting.
> > 
> > Well, at least Hoya didn't claim it was opaque ;)
> 
> This is an interesting message, yes it does leak light but it is
>  designed to pass light around about 720nm and longer wavelengths.

Keep in mind that filters have a factor called "cut", where the severity
of the transmission filtering is measured.  You won't find any filters
that cut absolutely at their specified point, but you will find a slope
that references the filtering in terms of the intensity of the incoming
light.  As a for instance, I can see the sun through my 87C, and that cuts
well beyond eye's ability to see that area.

george

---
Handmade Photographic Images
http://www2.ari.net/glsmyth/


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