But if you're a Weston lover like me, you can take heart in the fact that many of these beautifully crafted, selenium powered units are available on the Internet and elsewhere. The trick is to find one that hasn't been abused and still measures light reliably.
I did this by pointing them at a clear north sky between 10:00 AM and 2:00 PM. Imagine my surprise when I found that the needles on both units pointed to the number 320 at the exact centers of the two dials. This proved that the units were accurate. Surely, I thought, the Goddess of Light must have been smiling at me.
But when you're reading a poorly lighted scene, you flip the baffles down. When you do so, the number on the dials will auto-
matically change to reveal a new set of values for poorly lighted scenes. With the light baffles down you can see the honeycombed light gathering surface that covers the selenium photovoltaic cell.
The photo on the left shows the numbers that appear when you're reading a normal or bright scene with the baffles closed.
On the right you will see the numbers that appear automatically when the baffles are lowered for low light readings. Note that although the Weston meter was designed primarily for use in bright or normal lighting situations, it can still be effective in low light situations.
Then you use the tabs next to the blue dots to align the arrow with the number that corresponds to the number shown on the dial after you aim the unit at the scene you're photographing.
The black numbers on the silver dial show all the possible shutter speeds when they are matched to the white numbers that face them on the black dial.
For example, ideally in this example you could use f5.6/40, f8/20, or any other combination shown on the dial. Obviously, you'll have to make some small adjustments to conform to the settings on your camera.
Notice that on the left side of the arrow "A 1/2" appears while "C 2X" appears on the right of the arrow. The first setting would give you 1/2 the indicated exposure. The second setting would give you 2X the indicated exposure. These settings are useful for either flat scenes or scenes with excessive contrast.
In the illustration you will see a "U" opposite .8 and an "O" opposite 100. You can use these settings as follows. For a scene that has a wide range of tones, first set the arrow to the light value of the darkest area in the scene. Then set the arrow to the light value indicated for the brightest area. Finally, set the arrow midway between the darkest and lightest values indicated by the meter and make your exposure based on the midway reading.
But I wasn't lucky enough to find a Weston Invercone, which is a device you can attach to the meter that allows you to take incident light readings as well as reflected light readings. Worse yet, Invercones are at least as scarce as winning lottery tickets. If you have one you no longer use, I'd love to hear from you.