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 180 degree rule for timelapse 
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Joined: Thu Aug 15, 2013 6:40 am
Posts: 3
Post 180 degree rule for timelapse
Hey guys,

I've been lurking for awhile so I'd thought I'd ask my question to the members infinitely more knowledgable than myself. So, I've been reading up on the 180 degree rule. There seems to be two viewpoints as to what it even is. Some people describe it as:

A) the rule that if you are shooting 24 fps, you should have an exposure of 1/48th to keep the film look with minor blur.

B) the rule that if you are shooting a timelapse with 10 second intervals, you would want exposure close to half that to keep it from looking too choppy.

Now, both these rules make sense to me. Are both these rules part of the same bigger rule? These seem totally unrelated to me. My question is: Why, or does, rule A (above) have any bearing on rule B? Thanks for the help.

Daniel


Thu Aug 15, 2013 6:45 am
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Joined: Wed Nov 11, 2009 10:45 am
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Location: Merritt Island, Florida, Estates Unitas
Post Re: 180 degree rule for timelapse
I think it refers to mechanical motion picture cameras shooting on real film. The shutter was usually a metal disc with part cut away. As the disc rotates,the cutaway part passes between the lens and film, thus "opening" the shutter. Normally, the cutaway part of the shutter disc is about half (or 180 degrees). This means that the exposure time is half of the interframe interval. Both of your examples reflect this relationship in that the exposure time is half of the time between exposures. This will give you a look similar to what you'd get with the classic film camera.

In the digital age, we can simulate the film look by preserving the 180 degree rule, or we can take artistic license and vary the "shutter angle" by varying the relationship between exposure time and interframe interval. In most cases, the 180 rule makes nice looking shots. When I make my timelapse of sea turtles, I use the fastest shutterspeed possible to minimize motion blur and get the clearest images possible of the turtles. In other cases, you might increase the exposure time to create the impression of speed by allowing more motion blur.


Thu Aug 15, 2013 11:12 am
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Joined: Thu Mar 10, 2011 11:38 pm
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Location: Exmouth, Western Australia
Post Re: 180 degree rule for timelapse
The 180 degrees commonly used for film is a compromise between getting the longest exposure possible and having enough 'blanking time' to pull the next frame of film into the gate ready to be exposed. A longer exposure time would be preferred since it reduces the lighting level required or allows a narrower aperture if that suits your artistic requirements.

For a timelapse video you can extend the exposure for as long as you like, the limit being the minimum delay your camera can cope with between the end of one exposure and the start of the next.

The most important thing to understand in all this is that creating the ideal photograph of a scene is not the same as creating the ideal frame of video. Photography is (mostly-ish) about producing a sharply detailed, crisp image. Video is about smooth motion, which you will not get if every frame is pin-sharp. This is why we use ND filters on bright sunny days and whinge incessantly about aperture flicker if our chosen camera system can't do the 'lens twist' trick on high F numbers.

Kit


Thu Aug 15, 2013 5:26 pm
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Joined: Thu Aug 15, 2013 6:40 am
Posts: 3
Post Re: 180 degree rule for timelapse
Thank you guys, that is incredibly helpful.


Thu Aug 15, 2013 7:56 pm
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Joined: Mon May 06, 2013 8:55 pm
Posts: 30
Location: Houston, TX
Post Re: 180 degree rule for timelapse
To make it more confusing there is another 180 degree rule in film in regard to camera placement. http://en.wikipedia.org/wiki/180-degree_rule


Mon Sep 23, 2013 11:11 pm
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