Vintage Stuff Part 1: SEI Exposure Photometer
December 17, 2009 § 20 Comments
The cupboards and shelves at the Photographic & Video Services, my new job, are filled with old photo equipment, collected throughout the department’s history. In this new post series I’m going to pull some of the more interesting items into the strobe light. The first item is the SEI Exposure Photometer, a truly remarkable vintage gadget.
When I found this heavy metal rod thing, I couldn’t figure out what it was. The label suggested it was some kind of light meter, but it looked nothing like any other meter I’ve ever seen. A quick web search revealed that not only was it a light meter, but it is one of the most accurate reflected-light meters ever produced.
Produced by Salford Electrical Instruments (SEI) in the UK from about 1948 to the 1960s, it used to compare the brightness of a subject with the brightness of a lamp inside the meter. As the lamp’s brightness is predetermined, the brightness of the subject can be assessed and translated into correct exposure.
The comparing is done by looking through the 1,3x telescope. In it you see a spot in the center (actually smaller than the mock-up above). The spot is placed on the subject area you want to measure. You press a button to turn on the lamp, and then rotate the base of the meter to adjust the brightness of the spot. The correct measure is found when the spot disappears (above center).
Exposure settings can be read from the tables on the meter’s barrel. You can choose a shutter speed and find the correct aperture, or vise versa.
For the sake of illustration I used “measured” a part of the barrel in the example above. But to determine exposure you must measure the darkest part of the scene that you want to have detail (negative film), or the brightest part that you don’t want to clip (slides, movies, digital photography).
Although they stopped making it a long time ago, it’s still used by some Hollywood cinematographers for its extreme accuracy.
So the next time I’m heading over to the OR, I’ll bring this along, have it sterilized and measure those deep crevasses of the abdomen. Or maybe not.