Re: Previewing wood-effect

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

On 20 Oct 99 at 12:39, Oliver Pettenpaul wrote:

> Hello IR-folks,
> 
> I just received my B+W 92(#89B) and am really amazed. I can easily preview
> the wood effect throught the filter. Nice thing to have :)
> Ok, the wood effect starts at about 695nm, the filter has a 50% transmission
> at 720nm, so the human eye (I hope I am human...) must be able to recognize
> at least a little above that. Does anyone have numbers about the perception
> of the human eye regarding 'near IR' sight ? I know the figures vary from
> individuum to individuum...

At daylight intensities, the limit is 780nm (the lower limit is 380nm 
btw, both unlike the often claimed range of 400-700nm).

Note that this visual Wood effect can be made even a tad stronger, 
with a #88 filter (not to be confused with the more common 
#88A)....but it definately requires shielding your eye when looking 
through....to much false light from behind otherwise.

This is about the color my off-spec #87C filters are....;-((

--                 
Bye,

Willem-Jan Markerink


      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


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