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Exposing a starry sky?


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#1 Chris Keth

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Posted 12 November 2005 - 04:01 PM

Do any of you ahve experience in exposing a starry sky? I am doing some time lapse and I would like to record a night's worth of movement of the stars. The problem I foresee is in exposing it so that the stars are bright and, preferably, the sky has a little color and isn't black. My first approach would be spot metering a star and exposing it like a practical light source, but I can't fill my spot meter's taking area with a star. Should I spotmeter a blank piece of sky and place it appropriately and trust that the stars are bright enough to expose where I want them? I am going to be doing this pretty afr out in the country, so the difference between a star's brightness and the blank sky's should be pretty great.

Also, any advise regarding exposing the moon at night?
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#2 Phil Rhodes

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Posted 12 November 2005 - 06:41 PM

Hi,

You do realise you'll need many seconds per frame for that, right?

Phil
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#3 Patrick Neary

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Posted 12 November 2005 - 06:48 PM

standing out in a field trying to spotmeter an individual star sounds like the makings of a greek tragedy.

with the moon however, you just use the sunny-16 rule! (well, give or take depending on conditions...)

Edited by PatrickNeary, 12 November 2005 - 06:50 PM.

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#4 Tom Banks

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Posted 12 November 2005 - 08:17 PM

standing out in a field trying to spotmeter an individual star sounds like the makings of a greek tragedy.


haha, I can just imagine!

exposing the sky is possible on a still camera, shooting with an ISO around 800, f1.8, with a shutter speed around 2 minutes. but obviously it would be quite difficult to shoot this slow with film.
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#5 Tim J Durham

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Posted 12 November 2005 - 09:07 PM

haha, I can just imagine!

exposing the sky is possible on a still camera, shooting with an ISO around 800, f1.8, with a shutter speed around 2 minutes. but obviously it would be quite difficult to shoot this slow with film.

You can do time exposures with any film, I've done them with Pan-x (ASA 32).
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#6 Chris Keth

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Posted 12 November 2005 - 11:54 PM

You can do time exposures with any film, I've done them with Pan-x (ASA 32).



I can do with a black sky (I guess that was asking too much) but I'm just looking to get shining specks to move in some time lapse footage, are stars really that dim of light sources for that?
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#7 David Mullen ASC

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Posted 13 November 2005 - 12:16 AM

I can do with a black sky (I guess that was asking too much) but I'm just looking to get shining specks to move in some time lapse footage, are stars really that dim of light sources for that?


Why don't you take a still camera and shoot some exposure tests? That will tell you what shutter speeds you need to be using to record the stars with enough brightness.
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#8 Chris Keth

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Posted 13 November 2005 - 12:22 AM

Why don't you take a still camera and shoot some exposure tests? That will tell you what shutter speeds you need to be using to record the stars with enough brightness.



I plan to. I tossed this up to see if anyone had some advice to start me out. I'm definately going to do tests, though. That's what the nights early this week are for. I'm between quarters in school.

On the topic of school, I'll be getting dailies from my first shoot as DP for school. It's a 2 quarter project (meaning we get 20 weeks from preproduction to completion and screening) that's a quite well written, quirky romantic comedy about the value of a man's portfolio in a relationship. When I get them, I'll definately post stills.
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#9 Tim J Durham

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Posted 13 November 2005 - 12:22 AM

I can do with a black sky (I guess that was asking too much) but I'm just looking to get shining specks to move in some time lapse footage, are stars really that dim of light sources for that?

You'd have to look into the capabilities of the intervalometer available to the camera you're going to be using. I can't imagine there'd be one that would do exposures long enough to do what you want. You could use a still camera with a roll-film back. They make them for Nikons. That's 250 still photos but you'd have to take them manually with a cable-release at some interval and then transfer the photos to whatever format you're using.

I suspect most everyone does digital sky replacement of some sort but that's a guess.
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#10 Matt Butler

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Posted 13 November 2005 - 08:43 AM

To expose for a real starry sky where you can actually see the subtle colours in stars is possible but incrediblytime-consuming.I shot some star-plates that where used behind the title credits of a scholck sci fi movie called SPECIES (the original). The rawstock had to be treated in a pressure vessel with nitrogen gas purges followed by 'soaking' it in a mixture of hydrogen/nitrogen gas on location.

The treated rawstock has to be exposed very soon after otherwise the film loses its ability to pull in those in those pesky photons.Processing soon after becomes a priority because the film loses its increased sensitivity.

I'm sure wth the new Vision stocks, gas-hypering motion picture film would result in some stunning footage.

cheers
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#11 niknaz

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Posted 18 November 2005 - 02:06 PM

Do any of you ahve experience in exposing a starry sky?


Hi Christopher,

My thoughts: I've shot some time lapse at night with a Bolex and an intervalometer by Tobin Cinema Systems that has a "long exposure" mode. This particular motor has an option of shooting with the shutter open from 2 seconds to 50 seconds or 2 minutes to 50 minutes. There are a ton of variable that makes answering your questions hard, so I'm only going to comment on the work that I've done with this motor that relates to your question.

I shot time lapse of a moonrise in in a field in Ithaca, NY. I was using a 12mm--so my shot was wide. I shot 7279 with my lens wide open @ t2 and had the intervelometer set to a 50 second exposure. I printed a best light workprint to film and was quite pleased with the results. The sky is tinted blue--I wouldn't say it's super saturated, the trees are silhouettes and the moon moves smoothly through the shot. Now how did I get the 50 sec exposure time? Unfotunately through trial and error.

I've had some boo boos in the past. I really recommend going out with a still camera that can accept a polaroid back. That will help you figure out your exposure time on the spot. If I didn't have the moon in the shot, the exposure time would have definitely been longer and the movement of the stars would have been more like streaks. The sky usualy comes out tinted blue rather than black.

I've done some time lapse of stars and meteorshowers with not so good results. Mostly because I was shooting in the city where the night sky is light up and there's almost no way of getting clear star streaks.

As far as spot metering is concerned--if you plan on shooting the moon with a tight lens--use the spot meter. Otherwise, for the ammount of time you need to leave the shutter open to expose a star, it will be moving (or I guess technically *you* are moving) while the shutter is open so metering it will not be accurate.

Hope this helps.

Good luck!
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#12 Leo Anthony Vale

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Posted 19 November 2005 - 02:13 PM

Also, any advise regarding exposing the moon at night?


---The moon is illuminated by sunlight.
You should use the Sunny 16 rule as a starting point and open up from there to get a balance beween surface detail and glow.

Because the exposures needed for the moon and for the stars are so far apart you won't be able to geet them both in the same exposure, unless you're moon when it's just a sliver of a crescent.

Else you'll need to do a double exposure.

---LV
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#13 Luke Prendergast

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Posted 19 November 2005 - 03:07 PM

How is the Sunny 16 rule applicable to photographing the moon? An exposure equivalent to f16 with a shutter speed of 1/film ISO?
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#14 Leo Anthony Vale

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Posted 21 November 2005 - 03:31 PM

How is the Sunny 16 rule applicable to photographing the moon? An exposure equivalent to f16 with a shutter speed of 1/film ISO?


---The reason the moon appears glowing white inthe night sky is beause it is in daylight, it is illuminated by direct sunlight.

When one photographs a nght scene with the moon in it, teh moon will be a burnt out white highlight.
No detail.

---LV
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#15 John Pytlak RIP

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Posted 21 November 2005 - 03:42 PM

The Kodak website has information about astrophotography, with starting points for exposure:

http://www.kodak.com.../p150/P_150.pdf

http://www.kodak.com...150/p150a.shtml

http://www.kodak.com...troExpose.shtml
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#16 Luke Prendergast

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Posted 21 November 2005 - 03:59 PM

---The reason the moon appears glowing white inthe night sky is beause it is in daylight, it is illuminated by direct sunlight.

When one photographs a nght scene with the moon in it, teh moon will be a burnt out white highlight.
No detail.

---LV



And the application of the Sunny16 rule is?
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#17 John Pytlak RIP

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Posted 21 November 2005 - 04:06 PM

And the application of the Sunny16 rule is?


Another way of looking at photographing the moon is to think of it as just a big gray rock in the sunlight, and expose accordingly (if you want to see detail on its surface). Since the earth and the moon are essentially the same distance from the sun, the brightness of sunlight on a moon "rock" or an earth "rock" is the same, and requires the same exposure.

You may need to adjust if the moon is near the horizon or shining through haze, which may attenuate the light somewhat.
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#18 Luke Prendergast

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Posted 21 November 2005 - 04:33 PM

I was questioning the very tenuous link with the Sunny 16 rule, not how to get the right exposure.
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#19 Leo Anthony Vale

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Posted 21 November 2005 - 05:06 PM

I was questioning the very tenuous link with the Sunny 16 rule, not how to get the right exposure.


---To use that as a starting point for exposure tests for getting a balance between detail and glow.

& to point out the big difference in exposures between the moon and the stars.
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#20 Luke Prendergast

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Posted 21 November 2005 - 05:53 PM

The question is still unanswered; very simply: How is the rule applied to this situation? Step by step. What are the numbers and where do they come from?
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