Flash with large format

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Have never used flash with 4x5, but about to. The Vivitar 285 I use with 35mm has zoom capability...makes sure the flash is "wide" enough at 35mm focal length, and doesn't waste power at telephoto. I assume the calibration for these flashes is all 35mm "normal" when they say 50mm. Said another way, since if I'm at the same place with 35 and 4x5, and use 50mm and 150mm lenses respectively, I'm going to need to cover the same scene with flash, I assume I'd use the normal flash setting for both. Right?

-- John Sarsgard (sarsgard@yahoo.com), June 05, 2001


John: You are correct in your assumption of using the flash on the normal width for the 150 lens. There is no difference in using flash on a 4x5 or 35mm. I mounted a flash gun mount from an old 35mm camera on top of a Super Graphic is used to have and mounted my 235 directly over the lens. It worked great. I ran a cord from the shutter to the flash. You may need to drill out the center of the mount if it is one of the solid metal ones to keep from shorting the contact on the bottom of the flash.


-- Doug Paramore (dougmary@alaweb.com), June 05, 2001.

Calumet photo has a "rough" equivalency table for 35mm to 4x5. Should be good enough for flash use. I can't seem to get into their site right now, but:

Roughly, 150 to 165 corresponds to 50 mm, normal, 90 mm corresponds to 28 mm 120 mm corresponds to 35 mm 210 mm corresponds to 75 mm

One of the reasons pros use flashes with modelling lights & Polaroid test shots is to verify the lighting is right. If you've got a Polaroid holder, it is worth a test shot. Sometimes you don't want even lighting!

-- Charlie Strack (charlie_strack@sti.com), June 05, 2001.


One problem that you may encounter when working with a small flash on a 4x5 is that the typical aperture used is much smaller than one would use in a comparable situation with 35 mm. I do landscpae work, and am often working in the f32-f45+ range. I typcially employ a flash to highlight some aspect of the foreground. Because of the aperture, I find that I have to do 3-5 pops to obtain adequate exposure. This takes time. I'll do these with a 1/125 sec exposure, and then catch the ambient light with the predicted exposure. Just something that you may not have thought about.


-- Bruce M. Herman (bherman@gci.net), June 06, 2001.

John. A couple of daft things that can catch you out if you haven't used flash with a leaf shutter before.
Make sure the synch lever is on 'X', and that it stays there. These levers seem deliberately designed to be as easy as possible to knock off setting. Set it to X, and then tape over the damn thing!
A more subtle effect is that leaf shutters were really never designed to be used with the very short flash durations that modern auto-everything guns can give. The flash is sometimes triggered a tiny bit before the shutter has opened properly. This means that the lens is only open to, say f/8 or f/11 effectively, instead of f/5.6. So there's really not much point in trying to use your lens wide open with auto flash at close range.

-- Pete Andrews (p.l.andrews@bham.ac.uk), June 06, 2001.

When calculating equivalen focal lengths between 35mm and 4x5 to use a 35mm format flash, be sure to compare the narrow widths of the formats, i.e., about a 4x conversion, to make sure that the flash covers the entire scene.

If the flash covers a 50mm lens in 35mm, you can use no wider than a 4x50 mm = 200 mm in 4x5 at that setting.

(If that seems a little off, consider that the 50mm lens in 35mm format is not actually "normal" in the "focal length equals the format diagonal" sense. A normal lens would be a 43mm.)

-- John H. Henderson (jhende03@harris.com), June 06, 2001.

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