Spotmeter test - Sekonic 778greenspun.com : LUSENET : Large format photography : One Thread
I finally got around to test my Sekonic L-778 light meter this weekend.
UV: Test conditions were clear skies at noon, with and without UV filter in front of the lens, and then same test at night indoors. Ther was no measurable difference between outdoor and indoor measurements - in both cases the UV filter increased exposure by 0.1 stops.
Linearity: Using a B+W 8x ND filter, I mesasured at different light conditions from brightr sunny skies to lowest measurable light. The ND filter consistently reduced exposure by 3.0 stops.
Infrared: My kitchen stove has heaters that glow when heated. This affected exposure by 2-3 stops. My conclusion is that the meter is oversensitive to the near infrared spectrum. However, a hot but not glowing surface (such as a stove heater turned off after glowing) does not affect exposure. My conclusion is that the meter is not sensitive to the far infrared spectrum.
Beast regards, Åke
-- Ake Vinberg (email@example.com), May 13, 2002
I also have a Sekonic L-778 which I purchased for its flash spot ability. But I have tested it against a Zone VI modified Pentax digital meter, which I also own, and the Sekonic is far less linear in its response. Using a Macbeth colour chart in bright sunlight and T-Max film, the Sekonic was linear in its response for objects in the red, brown and flesh tone ranges, but showed reading much too low (as much as a stop and a half) for subjects with intense blue components, and too high (by a stop) for subjects with lots of green and some yellow components. The Pentax meter was linear across the board but a little bit inaccurate when reading very brights subjects, tending to produce readings that are too low by about a stop for the white or bright yellow patches. The Sekonic was more accurate in this respect. To sum up, the Sekonic L-778 is not linear at all compared to the Pentax meter and should be used with caution by Zone system practitioners.
-- David Kaufman (firstname.lastname@example.org), May 13, 2002.
Didn't think of using a MacBeth chart for checking linearity - that is of course a more challenging test. I do have one somewhere, so I'll try it out. /Åke
-- Ake Vinberg (email@example.com), May 13, 2002.