Re: Filter/Speed/Meter & DON'T meter using a Nikon Camera

["R. C. Lacovara" <lacovara@xxxxxxxxxxx>]

At 11:50 PM 10/3/00, you wrote:

>----- Original Message -----
>From: "Rolland Elliott" <rolland_elliott@xxxxxxxxxxx>

(Phillip Geller is responding to Re here... Eudora lost the thread, I 
think. Sorry for any confusion... Bob)


>Subject: Filter/Speed/Meter & DON'T meter using a Nikon Camera
>
>
>
>
> >You can still meter though an infrared filter on a Nikon camera, but the
>meter is not picking up lots IR light, it is picking up traces of other
>wavelengths, probably in the deep red area of the spectrum. Which exact
>wavelengths doesn't really matter that much. If it works for you, keep doing
>it. But don't imply to people that the camera is metering IR light because
> >it isn't
>
>
>Oh but it is. I put an ir led remote control in front of the lens of my F1
>with spd and
>blocking filter and the meter needle went up and down rapidly . I put it on
>a minolta
>meter with a spd and a blocking filter  intact and it changed from a reading
>of f 2
>to f 11. I would say that this shows that it is indeed reading IR.

I'd like to observe that the LED in remotes are quite "bright." They have 
relatively narrow output beams (well, 90 degrees, but not 270) and are 
designed to be seen by an IR pickup on a TV in a sunlit room. So in some 
sense you were really blasting the meter.

By the way, that is my experience: the meter flutters. That's because the 
remote is sending sets of pulses separated by pauses... the meter has time 
to follow the longer of the pulses.


>Just to be sure I took the remote into the dark room, left the lights off
>and looked
>at the led with a loupe to see if it even faintly glowed. It did not.
>The only reason that I can think of for an IR blocking filter on a spd would
>to
>keep the reading from being inflated by late or early morning sun when the
>color temp would be low  or to make the meter respond to tungsten light
>sources
>like it does to  5500K daylight.

Oh, it's emitting real IR, that's for sure. I use an image converter to 
"see" the LEDs, and they are quite "bright" in the IR.

I think that IR filters on camera meters are there to make the meter 
response approximate that of film... otherwise, your meter will not be 
measuring what your film records. Of course, films vary in their spectral 
response, but a little more or less in the UV or IR is a nit.

Bob

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