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Night Exposure Question


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#1 Alex Worster

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Posted 15 April 2008 - 01:18 AM

I'm doing some tests with the new Vision 3 stock and I want to shoot a night ext. time lapse-ish shoot of cars going over a bridge. I live in San Francisco so I've got access to some good bridges. I'm shooting s16 and plan to rate the stock at 320. I want to shoot at 4 fps to get some good light streaks and I've figured out my run time vs screen time and all that but what I'm unsure about is how to expose the shot. How would one meter for this type of situation and any suggestions on what stop to shoot at would be very much appreciated.
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#2 Michael Nash

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Posted 15 April 2008 - 03:39 AM

The exposure compensation for 4fps is straight forward math (+3 2/3 stop). Your base exposure (at 24fps) will vary depending on the location, and how you want it to look. You can use a spot meter or an incident meter to read strategic areas of the scene, and figure how bright you want them to appear in frame, and expose accordingly.

For an urban night exterior you're usually down about a T1.3 at 640 ASA, or T1.0 at 320 (24fps). At 4fps that puts you around a 2.8-4.0 split, but that's just a very rough estimate. You really have to meter the actual scene yourself.
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#3 K Borowski

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Posted 15 April 2008 - 06:43 AM

It is difficult if not impossible to use a meter reliably in this sort of situation. You need to do some sort of tests with C-41 or respooled ECN-2 stills. There are a lot of guides ot nighttime photography available online and in books, but they are only a starting point. You start to run into things like reciprocity and color temperature shifts when you get into longer exposures, though it looks like you have enough speed to avoid reciprocity in this particular situation.

What do you want your "normal" grey to be? Do you want the street lights to be color corrected or not color corrected? Do you want it to look like daytime, or actually look dark, like the night?

It's possible to expose the film so that it looks as if you're shooting in broad daylight. It's also possible to shoot in daylight so that it looks as if it is night (using the moon).

If you're shooting under mercury vapor or sodium lighting, it's impossible to fully color-correct, although you can get results that look very cool (not temperature-wise, mood-wise ;) ).

Again, more information is needed.

Edited by Karl Borowski, 15 April 2008 - 06:45 AM.

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#4 Tom Lowe

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Posted 15 April 2008 - 07:55 AM

Would it be possible to use a digital SLR still camera to take some test shots maybe?

Or just shoot the thing with a DLSR. Is this for a project that will finish digitally, or optical/chemical?
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#5 Frank Barrera

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Posted 15 April 2008 - 08:28 AM

'Michael Nash' date='Apr 15 2008, 12:39 AM'

The exposure compensation for 4fps is straight forward math (+3 2/3 stop).


You mean +2 2/3 stops right?
If base exposure is @24fps then 12fps is 1 stop, 6fps is 2 stops and 4fps would be another 2/3 stops= +2 2/3 stops

f
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#6 Michael Nash

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Posted 15 April 2008 - 01:48 PM

'Michael Nash' date='Apr 15 2008, 12:39 AM'


You mean +2 2/3 stops right?
If base exposure is @24fps then 12fps is 1 stop, 6fps is 2 stops and 4fps would be another 2/3 stops= +2 2/3 stops

f


You're right, it was late and I shouldn't have even been posting... :P +2 2/3 stops. So a little under a 2.8 maybe, depending on actual levels.

But it's not really that difficult to meter night exteriors as long as there's something you can measure, like a patch of sidewalk or area right under a streetlight. You just figure how bright you want that to appear in frame, and set your stop accordingly. Do some tests if you don't think you can count on your meter, but urban night exteriors aren't that dark.
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