I meter with a 35mm camera, and set it on aperture priority. This gives me an exposure reading fast enough that I can meter in the seconds before making a LF exposure. If the scene is tricky, I make sure when I still have some time to figure out where to point the camera to get the reading that I want.
Lars,
This is a very good question, and it's one I deal with regularly. Like you, I'm in outback Australia, dealing with those amazing colours around dawn and dusk.
I have reasonable success by checking the light meter during the exposure and extending or shortening the time. Unfortunately, I haven't quantified the process enough to give you a "hard and fast" rule to apply. I tend to set my aperture as I need for depth of field, open the shutter after making my first reading and check again at the half way point of the initial exposure reading (eg at about 60s if the indicated exposure was 2 minutes). If the meter now indicates 2½ minutes I'll give a total of 3 to 3½ minutes and call it quits.
In the morning, I'll do the same thing but give it around 1¾ minutes if the meter now indicates 1½ minutes.
I'm glad you're using Provia in this situation - it's easier to get it right with this method. I tend to use Velvia, and reciprocity failure defeats me often after sunset: the indicated exposure time increases by more than the time elapsed and you can never catch up without changing the aperture.
Good luck, and if you pass through Kalgoorlie on your travels, drop in and say hello.
Cheers, Graeme
Bear in mind that I have not done color photography with transparency for about 15 years, and that perhaps I am simplifying too much, but why not average the exposure?
For example, if you know you start at 8 min f/32 and you end up at 2 min f/64, why not do a 4 min at f/45? I know B&W is not the same, but this is what I do and has worked for me.
Or, why not make a double exposure? half and half.....
Anyhow, the problems is interesting, wish you luck and hope to see the pics somewhere someday....
Hi Lars
My opinion ( just for casual reading ok ... ) Since your are already there, might as well just take a shot i.e., just meter , compute ( based on scientific or gut feeling ) and shot, do not avoid the shot, cause if the picture is taken over a period of time, you actually do not know what subject ( eg moving clouds etc ) will be captured in it, you also do not know what color light ( changing light of sunrise ) will be captured, or if some wild dingo will wonder into the frame during exposure, so if you take a shot, at least you've got that shot.....
Err towards underexposure ( i'm sure you already do that ) cause an overexposed slide sucks
Finally , pack lots of film so that you can practice above theory of just shooting : )
Have fun Lam
I've started using a canon digital rebel as my meter. This really takes all the guess work out of getting a good exposure. You get an instant exposure preview, histogram, PLUS you can use it to frame the shot - which is really nice because I don't think I'll ever get used to that upside down and backwards thing. This method works well with all the films I use, both positive and negative. I bracket a lot less now.
Lars,
I shoot both Veliva and Provia 8x10 in early morning and late evening light. For my subject matter, I typically aim for a two minute exposure. So if my metering indicates f/64 @ 2 minutes, then that's what I shoot in the morning and let the increase in light level over the two minutes compensate for reciprocity effect. During the evening, I simply open up one stop and shoot at f/45 @ 2min. This simple formula has worked great for me.
Best of luck and have fun.
Mike
I'd like to know how you manage to connect to the internet when you're 630 miles down a dirt track in the middle of the australian outback?
satellite phone?
I shoot Provia but not as dark as what you are doing. Of course the darker the more difficult getting it correct becomes. This last year I nailed three really important dim images where I could not bracket and brought back winners. But they were only at about EV9 to 12. Of course have taken some low light images which did not come out so am not too confident either. For my film I like to use my digital meter in incident mode perpendicular to the area of the sky area that is illuminating my target. Then decrease about 2/3 EV and cross my fingers. Tis really the most difficult decision in large format work. ...David
Lars, I have put together a spreadsheet that calculates correct exposure for varying light conditions. You are welcome to it. I assume that since you are on this forum that you have access to a computer.
There are two variables that must be input to the spreadsheet: the manufacturers recommended reciprocity correction and the rate at which the light intensity is changing. It assumes that the variation in light intensity is linear, which is a reasonable assumption over short periods of time ie. 8 minutes or less.
For the example calculation I used Fuji Velvia 100. Fuji states the following corrections for reciprocity failure: add 1/3 stop @ 2 min., 0.5 @ 4 min., 2/3 @ 8 min.
This is the range of metered times that I have used for my example. The range can be extended if the reciprocity charecteristics of the film are known in the range of interest.
This method uses the average light intensity over the given time period. Integration would be more acurate, but I wanted to keep this quick and simple. Over a short time period the results will be a reasonable approximation.
What I found is interesting and verifies what some posters have said, that when the light intensity is increasing they shoot using the metered exposure and let the increase in light account for the reciprocity correction. For metered times between 2 and 8 minutes and light intensity rate of change between 0.1 and 0.2 stops/minute this method yields an exposure that is less than 1/3 of a stop from the correct exposure. Good enough for negative but pushing it for chromes.
I will post this and then try to post the spreadsheet formulas.
Attached are the spreadsheet formulas from my previous post.
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