Film/System exposure calibrationgreenspun.com : LUSENET : Large format photography : One Thread
I would like to run some film tests to calibrate Velvia to my Sekonic 508 to my brand new to me (Wisner PE) to my new 180mm Sironar-S. What do you do when adding a new film, system, or component to give you confidence in your exposures? I want to be as efficient as possible in understanding this new system I have procured.
Are there any Best Known Methods (BKMs) that are suited for the above desires?
Would you calibrate to your 35 mm if you intended to use it in concert with large format. Could you run tests in 35mm that could be transferred to the 4x5.
-- Jeff Rose (firstname.lastname@example.org), February 17, 2001
Shoot some film. Easy enough. James
-- lumberjack (email@example.com), February 17, 2001.
Jeff: I would run some tests of your primary subject (scenics, people, etc.) and include a grey card. I would make the test shots at different shutter speeds or get the shutter checked out on a speed tester. In LF, it seems to be more important for the slower speeds to work well and within limits, as small aperatures are most often used. As for using a 35mm and transferring the data, that seems improbable. You cannot even use an identical LF setup to test against another lens-shutter combination. The lens, including shutter and aperature, is the deciding factor for precise tests. The test will not really be valid if you change lenses due to the amount of shutter and even aperature error. Though both may be within specification limits, one may be on the high side of the tolerance level and the other on the low side. I wish I could tell you of an easy, cheap method to do the testing, but I haven't found one. Good luck with it.
-- Doug Paramore (firstname.lastname@example.org), February 17, 2001.
I would second the above advice except recommend a Color Checker card instead of a gray card if you're using color film. If you can borrow or rent one, a polaroid back might be handy as well since it will let you evaluate your exposures on the spot and fine-tune the ranges that you need to test more carefully with film.
-- Jeffrey Goggin (email@example.com), February 18, 2001.
Colour reference cards seem to be quite difficult to come by lately, but the paint colour charts that you can pick up in any DIY store make excellent reference cards. Emulsion paint samples have a nice non-reflective finish, and come in quite saturated colours nowadays. The united colours of Benetton card has a nice rainbow of both saturated and subtle colours. And the price is right!
-- Pete Andrews (firstname.lastname@example.org), February 19, 2001.
You could also use a Kodak color bar (Color separation guide/grayscale ruler). You might also want to make sure you shoot film from the same emulsion batch. We'll occasionally test emulsions by shooting against a studio gray backdrop, with the color bar, and some objects that give us a good range of tones, maybe a specular highlight as well, sometimes we'll use a hand or something for a skin tone. But, we buy film in bulk, and run our own E6, so this narrows down the variables a bit...make sure you take good notes.
-- DK Thompson (email@example.com), February 19, 2001.