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Is there a trick for timing passing clouds?


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#1 Alexa Mignon Harris

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Posted 09 August 2008 - 06:53 PM

Hi! I wanted to know if there is a trick or tip for timing passing clouds on partially cloudy days. I know the finger trick for timing how many minutes I have before the sun sets on the horizon. Is there something similar for clouds?

Edited by Alexa Mignon Harris, 09 August 2008 - 06:53 PM.

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#2 Phil Rhodes

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Posted 09 August 2008 - 08:09 PM

If you find one, please let me know.

But if you think about it, there can't possibly be - any variation in wind speed, cloud altitude or sun angle will affect the speed at which the shadow moves across the ground.

P
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#3 Daniel Wallens

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Posted 09 August 2008 - 08:17 PM

The earth moves at a constant speed around the sun, that's why we can determine its position (and hence the thumb trick).

With clouds, however, it is different. Wind speeds are different and changing depending on where you are, the day, the time of year, season, etc. Also, keep in mind that wind speeds are much different on the ground from where they are at the altitude that the cloud is at. On top of this, different clouds exist at very different altitudes. On top of this, clouds change size and shape as they move through the sky. A small cloud in the east may dissipate when it travels more west (could be a distance of a few thousand miles, at least). So unfortunately, there really isn't a set "trick" to use in all situations for measuring when a cloud will be at a particular location, how dense it will be, or what size/shape it will be.

The best thing you can do is keep tabs on the sky. Speeds of clouds generally don't vary minute to minute. If you see clouds moving fast, you can judge for later. Watch clouds during your downtime, and then you will be able to give better estimates to your DP when it's time to shoot. Have your best boy or production stay on their computers, and let you know what the windspeeds are like for your area (and weather in general, is a good idea). Over time, you'll get better at knowing what "40 knots" or "5 mph" looks like. Mostly, though, I find just looking up helps more than anything.

:)
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#4 Satsuki Murashige

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Posted 10 August 2008 - 02:09 AM

What's the finger trick? :huh:
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#5 Tim Terner

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Posted 10 August 2008 - 02:36 AM

What's the finger trick? :huh:


I went to post the same question Satsuki and then saw yours, but googled it and found this http://www.wikihow.c...t-Before-Sunset
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#6 Jonathan Bowerbank

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Posted 11 August 2008 - 12:24 AM

A DP I'm working with did this the other day, and it was pretty accurate. It's especially useful if you're shooting in a hilly area, while Production scheduled the day according to when "sunset" was...which could sometimes be HOURS after you lose direct sunlight
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#7 Satsuki Murashige

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Posted 11 August 2008 - 01:22 AM

I went to post the same question Satsuki and then saw yours, but googled it and found this http://www.wikihow.c...t-Before-Sunset

Cool, thanks Tim!
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