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 Interval cutoff for star pan 
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Joined: Wed Dec 08, 2010 4:18 pm
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Location: Tahoe, CA
Post Interval cutoff for star pan
Hi guys...I came across this excellent timelapse of the Milky Way above Lake Tahoe:



which utilizes 30 second exposures and 5 second interval between exposures over ~9 hours.

As I will be using a dolly to pan through the timelapse, I would like to push the interval to 10 seconds to allow for more time for the motor to move the dolly along the rail.

Does anyone have experience in this area in terms of what the longest interval between 20-30s exposures of stars can be in order to produce useable results in the final video?

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Wed Jan 05, 2011 6:10 pm
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Joined: Tue Jul 08, 2008 12:36 pm
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Post Re: Interval cutoff for star pan
Are you talking about doing a move-shoot-move setup?
If you are doing constant movement it would not matter.

As to how long still looks good, there are a lot of factors, like they type of lens used etc, and personal taste for the final look.

If you want smooth looking video rather than sharp individual frames I would go with constant movement, and short intervals, at least as much shutter open as shutter closed/travel time, the longer the exposure and shorter the interval better.

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Thu Jan 06, 2011 4:40 am
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Post Re: Interval cutoff for star pan
Hi Antz, thanks for your reply.

Yes, I am talking about a move-shoot-move setup. I have a 16-35 Canon lens on a 5DII, shooting typically at 16mm, f/3.5.

This may be a dumb question - but how can I use a continuous move with my dolly if the camera shutter is open and expsing? Won't everything (including the stars) be blurry?

By the way, here's the shot I made last night, with my DIY dolly:



This is ~100 frames, over ~ 1.5 hours, 30s exposures with 10s intervals. In the middle of each 10s interval, the dolly gear motor moved the carriage and camera for 6s. We had frost and power failure (it was 11 degrees out!) at 1.5 hours, so we only made it 1/3 of the way along my 1m track. The ultimate reason for answering this question is whether I can have an interval of say 20s between 30s exposures, and still get a smooth video result.

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Thu Jan 06, 2011 8:59 am
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Post Re: Interval cutoff for star pan
Yeah, I don't see how you could shoot with continuous movement if your exposure time was long... Move shoot move seems like the only way to do it.

Anyways,
I love your timelapse. That's an amazing view. I'd ditch the chain in the shot, but hey, it was just a dolly test right?

I'd say 10 seconds would be fine if it was an all night 'lapse, but the frame rate would have to be a bit faster than normal on the final product. What frame rate was that test shot compiled into? 24p?

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Sat Jan 08, 2011 12:58 pm
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Post Re: Interval cutoff for star pan
Basically it boils down to what you want to do with the final product.
Motion blur actually makes a video look better.
If you want sharp still shots to be able to use the still shots on their own, then you want move-shoot move.
Even with continuous motion on star shots, the motion is so small it will be barely noticeable.
Have a look at Tom's stuff on the timescapes home page, I believe most his stuff is all continuous motion.

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Sun Jan 09, 2011 11:24 am
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Post Re: Interval cutoff for star pan
Interesting. I haven't tried it yet, but I just assumed continuous movement would ruin the whole shot for the long exposures. I guess I'll have to do some experimentation.

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Sun Jan 09, 2011 2:13 pm
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Post Re: Interval cutoff for star pan
DigitalVideo wrote:
but I just assumed continuous movement would ruin the whole shot for the long exposures


A quick calculation should help (in metric).

Let's say you move 1 m in 3 hours taking a frame every 20 secs (~ 20 s exp). That's 1000mm/540 frames = 1.85mm per frame. Unless you have very close foreground, that sort of movement will barely show in the final shot.

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Sun Jan 09, 2011 2:59 pm
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Post Re: Interval cutoff for star pan
Thanks for all the replies and comments. I'll have to try some continuous move shots this weekend with my dolly setup.

Funny you brought up that chain DigitalView...as I'm sure you know when you set up a shot like this so much focus goes into the gear setup and functionality that I didn't really think enough about what the resultant shot would look like....I was concentrating on having the chain in the frame to show relative motion, but didn't think that it would block the fog. D'oh! As I'm new to timelapsing I'm very much still learning, and I really need to focus like I do in my traditional landscape photography about the composition being the most important thing. Luckily it was shot after work in my hometown so I can just go back another night and try again.

Anyway, check out another shot made with my setup at Death Valley:



Hoping to get to the coast this weekend...cheers again for the advice and guidance.

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Thu Jan 13, 2011 10:00 am
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Post Re: Interval cutoff for star pan
That Death Valley one is really good.

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Sun Jan 16, 2011 8:27 pm
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