Re: Melles Griot filter info

[Foamb <cpurdum@xxxxxxxxxxx>]

well, the article stated that (in the meters he was using) there was a
light blue infrared blocking filter in front of the photo diode and thus
he could not get accurate readings using the method of placing a #87
over the front of the meter. He disassembled the meter and replaced the
IR blocking filter with the #87 and the Melles Griot 03SWP622 to limit
the meter to reading light only in the film's (HSI, HIE) sensitivity.
The only meter that was specifically mentioned was a Pentax digital spot
meter, and that it was difficult to modify. He said that he had modified
several other incident and reflected meters using this method. The main
point was that the modified meter would give accurate readings in dim lighting.

My plan is to disassemble the Luna Pro Digital, remove the IR blocking
filter (if any) and if there is room for the #87 and 03SWP622 filter,
I'll add both and compare exposure to using the meter with just the #87.
I might also contact Gossen prior to disassembly and see if I can find
out what range the Luna Pro Digital is sensitive to. might make things easier.

Chris

> Aha....mmm....this begs the question why anyone would mount such a
> deep-IR sensitive sensor in a lightmeter that normally is only used
> to read visible light....whatever it misreads for IR film because of
> this, it would misread perhaps even more for visible applications
> (perhaps the relative amount of error increases?....only a tiny
> amount of wanted IR, and still the same amount of unwanted IR).
> 
> (in which case the design should include a IR-block filter right from
> the factory)
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