Re: WJ & light leakin Hoya's

[Cameron Shaw <cameron@xxxxxxxxxxxxx>]

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.
( Hoya R72). However I am of the opinion that it is just on the
border of visible/invisible light to the human eye.
 Try this experiment, to shield your eye from unfiltered light,
attach a piece of black card/paper around your R72 filter to form
a short tube, and look through the filter at some green foliage
in bright sunlight. It will take a few seconds for your eye to
adjust, but you will be able to see a faint infrared woodeffect
image of the foliage, you are seeing visible near-infrared light.
 I was amazed that it was possible to see this, so I would suggest
that the filter is working and you are seeing an infrared image
of your light bulb filament.
Cameron.
*
****
*******
******************************************************
*  To remove yourself from this list, send:          *
*         UNSUBSCRIBE INFRARED                       *
*       to                                           *
*         MAJORDOMO@xxxxx                            *
*----------------------------------------------------*
*   For the IR-FAQ, IR-Gallery and heaps of links:   *
*  http://www.a1.nl/phomepag/markerink/mainpage.htm  *
******************************************************