RE: light meters?

Hi Eric,

Here is the method that I teach students in pinhole workshops. I worked out
this method when my light meter was a Gossen Scout (about as inexpensive as
you can get, but since broken and replaced with a Sekonic L-508). It is
based on the EV scale, which my old scout had.

~~~~~~~~~~~~~
Each camera and film combination has a Magic Number. This is the length of
exposure in bright sunlight. You can learn the Magic Number if someone
tells you, or by trial and error or by testing.

If you use a light meter:
- Determine your meter's EV constant for a bright, sunny day.
On a bright, clear day, go outside and take a meter reading in full sun and
note the Exposure Value (EV) FOR A SELECTED ISO SPEED. Incident metering
works great for taking this measurement, or you can use reflective metering
and a gray card. I've found that, with my meter and here in Minnesota, the
bright sunny day EV is always close to 15.5 at ISO 100.

Then, when making an exposure:
- Measure the exposure value of the ambient light USING THE SAME ISO
SETTING.
- Determine the difference between the two EV readings.
- Adjust the exposure time as needed.
For example, bright sun is EV 15.5 and the scene you are photographing
meters EV 13.5. This is a difference of 2 EV. Since 1 EV is equal to 1
stop, you'll need to give the exposure 2 extra stops. For a magic number of
15 seconds, this would be a 1-minute exposure, since 15 x 2 = 30 and 30 x 2
= 60.

If you don't have a light meter, adjust according to this table:
 LIGHT CONDITION.... ADJUSTMENT........ ADDITIONAL STOPS
  Bright sun........ None.............. None
  Haze in sky....... 2 times as long... Add 1 stop
  Slight overcast*.. 4 times as long... Add 2 stops
  (*you can see the
   outline of the sun)
  Heavy overcast.... 8 times as long... Add 3 stops
In early morning or late afternoon, double the times listed above (add 1
more stop)
~~~~~~~~~~~~~

A big advantage of this method is that you only need to keep one number in
your head, the magic number of the camera / film combination. You don't
need a meter that deals with tiny apertures or tiny ISOs. Since reciprocity
failure is inherent in the magic number, you don't need to adjust for it
when making an exposure. I've used this method successfully in scenes from
bright daylight to indoors at 10 stops less than bright daylight.

I give the students the magic number for the cameras we make in class. I
also discuss and show examples of the testing procedure I use to determine
the magic number; but sometimes less experienced students get lost.

Hope this helps.

Tom

> -----Original Message-----
> From: owner-pinhole-discussion@spitbite.org
> [mailto:owner-pinhole-discussion@spitbite.org]On Behalf Of Eric S.
> Theise
> Sent: Wednesday, June 16, 2004 12:47 PM
> To: Pinhole Discussion
> Subject: [pinhole-discussion] light meters?
>
>
> Hi everyone,
>
> I use an old Sekonic Studio Deluxe II light meter for my work. At the
> time I bought it, it was what every experimental filmmaker
> used (probably
> still do), and I have no problems with my own use of it.
>
> But, as I teach my workshops, I find that the first
> investment students
> should make, if they're going to get serious about photography, is a
> light meter.
>
> And so I come to you for recommendations. Analog or digital, but
> relatively inexpensive at retail, and ideally with a range
> that extends
> down into our territory, where we have f-stops in the
> hundreds and ISOs
> in the single digits.
>
> Thanks in advance... Eric
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Received on Wed Jun 16 21:28:57 2004