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Talk:Rotary disc shutter

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the calculation-formula is wrong??[edit]

I would like somebody to dubbelcheck this, but the

Shutter Angle/360 = Exposure Time/Frame Intervall

formula is wrong, it doesen't come out right. for example: a pretty usual set of numbers for this would be a shutter angel of 180, which would at 25 fps give us an exposure time of 50 (1/50 of a second) hence:

180/360 = 0.5

50/25 = 2

2 does not equal 0.5 obviously. but what does come out right is switching the place of "shutter angel" and "360"

360/Shutter Angel = Exposure Time/Frame Intervall ==> 360/180 = 50/25 = 2

Seems like an honest misstake, but can somebody confirm this so we can change it?

Thank you.

EDIT: Actually, Im pretty shure this is the right way to go, so I changed it, please somebody call me on it if its wrong. first time wiki-ing =)

Thank you

—Preceding unsigned comment added by Theharis (talk • contribs) 23:04, 24 February 2009 (UTC)[reply]

Just in case anyone else has this same confusion: the mistake above is using 50 as exposure time and 25 as frame interval. The correct values are 1/50 and 1/25 respectively. ScottJ (talk) 21:49, 16 April 2012 (UTC)[reply]

The article refers to 24p as "actually 23.976" ... says who?? Film is 24 frames per second, commonly displayed as 23.976 Hz on video displays due to legacy reasons (NTSC being 59.94 Hz or something like that). But this article is about film, not video, and 24 fps is more accurate/correct than 23.976 Hz. ScottJ (talk) 21:39, 16 April 2012 (UTC)[reply]

I went ahead and changed the article. ScottJ (talk) 21:47, 16 April 2012 (UTC)[reply]

- To be fair, I thought these days most film was shot at 23.976 to keep a straightforward workflow from big screen to DVD/BluRay and all manner of TVs, since films get shown on these formats eventually. So, really when people are recording at 24p, they actually are 23.976 usually. Isn't that right? I know there's a lot of variation in the industry too, but I believe that's becoming fairly standard.

Otherwise, you have to slow down the film during telecining, and sacrifice the audio rate a bit. — Preceding unsigned comment added by 66.91.95.72 (talk) 06:28, 22 December 2012 (UTC)[reply]

This is the reason of the rule-of-thumb "Use an Exposure Time twice the value of the Frames-per-second to get normal motion blur".

I get what the article is trying to say but from a purely mathematical standpoint it makes no sense.
Take 25fps = 0.04 of a second. Now use an exposure time twice this value 0.04 × 2 = 0.08 or 1/12.5 of a second.

What they are saying is. 25 × 2 = 50
25(fps) × 2 = (one)50(th of a second exposure time)

But it confused me. A rule of thumb is supposed to be for the layperson. — Preceding unsigned comment added by 122.57.209.40 (talk) 05:46, 26 February 2014 (UTC)[reply]