Sub-zero shutter speed accuracy?

[Scott Kathe]

The title just about sums it up. I was out running a roll of Velvia through a bargin F3 I got from KEH to make sure it worked. I was using incident metering from about two hours before sunset up to sunset and it was below zero F. All the 135 F3 (new-fangled electronic shutter) shots were spot on while the two 4x5 Velvia films look like they were overexposed by about one stop. I was using a 150mm Nikkor-W f5.6 in a Copal 0 shutter. The shutter was set at 1/4 sec and f32-that combination doesn't seem to fall in line with the sunny f16 rule even though the sun was very low. The thing is all the F3 slides look great and I used the same metering method for both cameras. Any ideas?

[Glenn Thoreson]

Leaf shutters slow down and even quit working in sub zero temperatures. You can send it in and have all the lubricant removed and that helps. There is supposed to be a special lube for arctic conditions, also, but I have no experience with it. Even totaally dry and lube free, it will be a little slower due to the nature of how metal springs and such respond to extreme cold. If your shutte hasn't been serviced recently, it may be worth a CLA and lubed with the arctic stuff anyway. It depends on how often you plan on shooting in those conditions, whether it's cost effective.

[Scott Kathe]

Thanks Glenn,

Last night I was thinking about the 1/4 second exposure and if I remember correctly the shutter sounded more like 1/2 second the other afternoon. When it gets that cold again I'll take the lens outside and fire it at 1 second and time it with a stop watch. Oooh, maybe I'll put it in the freezer instead of waiting but I'm concerned about condensation.

I think the 1/4 second at f32 was correct. It was cloudy last night so I couldn't check my exposure under similar lighting conditions. This morning it is nice and sunny and the sun is the same distance above the horizon as it was the other afternoon and the incident reading is 1/4 second at f32!

Scott

[Mark Sampson]

Copals are usually pretty accurate and reliable. I don't remember shooting large format when it's that cold, though. 15F is probably my lower limit. However, it would be worthwhile to get that shutter's speeds checked at normal temperatures- something might be going on that needs adjustment. And if you're going to shoot chromes it's good to know exactly what your shutter speeds are- more so than with (more forgiving) negative materials.

[David Crossley]

I shoot all the time in sub zeroe temperatures. If it,s a keeper image and i notice the shutter does'nt quite sound right, i will stop down enough to put me into bulb and then manually time the exposure.

Having said that, an off sounding exposure has never turned out wrong (touch wood). Forget where i heard this about bracketing<when you are in the field, film is your cheapest commodity>. Good insurance and peace of mind till your film is processed.


David Crossley/Crossley Photography....

[Gene McCluney]

All mechanical shutters (such as found on large format lenses) are prone to speed variation depending on temperature. If a shot on large format transparency film is critical you should do a time-exposure with your stopwatch. (Of course I am refering to scenics). If you were shooting b/w or color negative, the latitude of the film would have enabled you to get a keeper, even with the shutter slow-down.

[Scott Kathe]

I agree for black and white it isn't much of an issue I have also thought about setting the f stop so that I would have a 1 second exposure or longer and using the B or T setting, but I really don't want to be shooting at f64. Neutral grads or a polarizer would give me longer exposures at a given f stop. Maybe a stopwatch to check the shutter speed at 1 second and extrapolate backwards? I'm guessing it's non linear, but probably good for maybe 1/8th second and slower?

Scott

[Gene McCluney]

You can do what us working pros always do and shoot a Polaroid test. Of course to process it you will have to put it in your armpit if it is cold outside, or go inside to process. But I would never shoot a 'chrome on a job without a test first. With Polaroid testing, it doesn't matter how accurate your shutter is, as long as it is consistent in its operation.

[peebs]

Hi Folks,
I'm just getting into LF and am leaving for Yellowstone this weekend. along with the other formats I use I am hoping to use my LF camera also. It will be cold up there! I have some Polaroid type 79 (iso 100) to use for testing but am curious about trying to developing it in the extreme cold. Any words of wisdom?
Thanks

[Glenn Thoreson]

Pull it and stick it in your arm pit or under your coat, next to your body, while it develops. It's been COLD up here. If you use batteries in anything, keep an extra set in your pocket. If you're going to be out in the cold for extended periods, a couple of chemical hand warmers in one of those little coolers would be a nice thing to keep you shutter in until you're ready to shoot. It will slow down or quit if it gets too cold. Enjoy!
Edit: Use caution when bringing cold equipment into a warm place. Condensation can hurt it. I would carry some plastic bags to put stuff in before entering a warm place. Keep it tightly sealed until it warms up. Warm into cold is not a problem.