[pure-silver] Re: Basic question on light
- From: Sauerwald Mark <mark_sauerwald@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 30 Mar 2005 07:30:30 -0800 (PST)
---
> >If I use my spot meter, and it tells me - for
> example
> >to expose for 1/60 at f16 for 100ASA - what is the
> >intensity of the light at that point in lumens?
>
>
>
> A spot meter reads the reflected light.
Jim, let me rephrase the question....
"What is the intensity of the light being reflected
from the metered surface in lumens?" - I believe that
there should be a correlation - my guess is that it
should look something like:
A*T/F^2 = K*ln(I)
where A is the rated speed from the lightmeter (ASA)
T is the shutter speed (Time that the shutter is open)
F is the F stop - A being set on the meter, T and F
being read from the meter.
K would be some constant, and I the refelected light
intensity in linear units such as lumens.
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