Bewi Super L Meter
I'm thinking of buying a Bewi Super L light meter but before i need to know if it gives exposure values of more than 30 minutes.
I've tried to look for this information but nothing so far, hope anyone here can help me.
The scale of the Bewi Super goes up to one hour, but this alone does not say anything about its sensitivity.
I'm going to photograph with ektar 100, inside a camera obscura
In general, a lightmeter will not give you directly exposure times in 10's of minutes. Neither will it have provisions for the f-numbers of a pinhole camera (camer obscura). But that is the easy part: say, meter indicates 1/125 f/16.
"Equivalent" (read below) exposures: 1/2sec f/128, 1sec f/180, 2sec f/256, etc... but only a starting point.
The hard part is reciprocity law failure. And the meter won't help, even if it has markings up to 30min and f/256.
the link you sent is for the Bewi Super, the one i am talking about is the Bewi Super L...
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yes, the reciprocity failure is yet another thing i'm trying to solve. can't find experiments on more than 5 minutes exposures
Originally Posted by bernard_L
I'm am shooting with a Sinar, inside a camera obscura (my room) so the f-numbers are not the pinhole. I just needed to know if the Bewi Super L would work in such a weak light...
-) to my knowledge (Internet...) the Super and the Super L have the same metering circuit
-) I don't know the sensitivity of that meter. Someone could check against one of those most sensitive meters. But that won't help you as you don't know yet the luminance in question...
Originally Posted by AgX
i'm not really pro in this photographic concepts: what do you mean with luminance?
I've already made some photographs in the dark room but with digital, i know to relation between the sensitity of the digital to the analog is not very diferent (except in the reciprocity failure thing), i am now simullating with the digital what may happen with the sinar...but it still isnt very accurated
Luminance = "Brightness" of your subject (in this case the reflection from your chamber wall.
For proper working of that meter you need a mercury battery. Have you got one??
(Or a well made electronic substitute?)
I just checked my sample:
the needle starts to move about 1/2 stop outside the range of that red digit one has to operate (which I intreprete of sign of good working condition).
And that most extreme position is equivalent to
1h @ f32 @ 100ASA
The sensitivity of that meter would thus be EV +2 .
Last edited by AgX; 05-23-2013 at 08:16 AM. Click to view previous post history.