Re: hoya R72 Filter

["joe b." <joe-b@xxxxxxxxxxxx>]

In message <199608211057.LAA06377@xxxxxxxxxx>, Willem-Jan Markerink
<w.j.markerink@xxxxx> writes
>Apart from the difference, the big question is: did you test it 
>indoors or outdoors? I can't see much through either filter 
>indoors....;-))

Indoors. 

>Further note that 5 or 10nm is not much technically, but has a large
>effect on the human eye (either as color difference in normal
>filters, or darkness differences on the visible limit of infrared.

That would explain it, I suppose.
 
>Even different batches of Schott glass (used by B+W, Heliopan,
>Rollei etc) can show this difference. Actually, even (Wratten)
>gelatine, know as the tightest spec filter, had a margin of 10%.

And I have a feeling the IR result will be the same from both of these.
If I can  remember to switch between them next time I use one, and note
the frame number, all will become clear no doubt.
-- 
joe b.

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Topic No. 4