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Daniel D. Teoli Jr.

Short explantion of how shutter speeds work

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" When shooting at 25fps, your shutter speed should be 1/50 of a second.

If your camera can shoot at 50 or 60 fps, your shutter speed should be 1/100 or 1/125 of a second.

The reason for this 180-degree rule is because it helps us to record video that contains natural movement. ,,,,,, "

 

It's not clear for me. Can you tell me why ? 

If I shoot at 25fps the minimum shutter speed to have natural movements is 1/25 of a second … or not ?

 

Thanks in advance.

 

 

Edited by Vincenzo Di Salvo

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If you shoot 25 fps with no shutter / 360 degree shutter angle / 1/25th shutter time, you have twice as much motion blur per frame than when you shoot with a 180 degree shutter angle / 1/50th shutter time.

Now which looks more "natural" is subject to debate since we don't sample reality only 25 times per second.  But most people feel that the 180 degree shutter looks more like classic film and no shutter looks more like classic interlaced-scan video (which was usually shot with no shutter).  It's just conditioning but you're not going to break it in one movie when everyone else is using a 180 degree shutter angle.  It's not a question of which looks more natural, but a question of which looks like you're watching a regular movie and which looks like you're watching a live news broadcast.

But don't take anyone's word for it, go out and shoot some moving scenes at 25P with no shutter and see what happens.

Part of the problem is that sampling motion only 24 or 25 or 30 times per second is on the low side if you are trying to create the illusion of continuous motion.  So too short a shutter time and you become aware of each discrete frame, but too long a shutter time and you get a lot of blurring, more than seems natural.  If you were shooting and showing everything at 300 fps, for example, you'd probably be less worried about shooting with no shutter and the image would feel more like how our eyes see things.

 

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NTSC television had a 17.2 percent horizontal blanking interval, PAL 18.8 percent. The vertical interrupt was about 8 percent with both systems. That corresponds to roughly 30 degrees shut angle, 330 degrees exposure. All in all, the images displayed corresponded to such taken in a camera with a 290 degrees shutter opening. The film camera I know of that has the widest opening was presented in 1934, a Mitchell tuned to 270 degrees by a George Schneiderman for Fox. Among the cameras for 16mm film the 1949 Nord has the largest shutter opening of 240 degrees, followed by the Mitchell 16 having 235.

Cinema, with rather few exceptions, let us in the dark for half the time in addition to half the action not recorded. IMAX has a light-dark ratio of around 2 to 1 (68 percent light, IIRC) but the cameras work at 180 degrees open and closed, some at 155 or 150 open. There were shutterless toy projectors such as the 8mm Kenner and Minelec by Meccano where the film is withheld by a metal tongue in the perforation and pulled on until it slips one hole further. This happens very quickly but you have motion blur now during screening.

To emulate film with video I find idiotic. Isn’t it a big advantage of—digital—video to be able to record and reproduce motion for 100 percent of the time? Every film pioneer would have wanted it. At least film projection without dark pauses is feasible, the Skladanowsky had it in 1895, Green & Prestwich in 1896.

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To emulate film with video I find idiotic. Isn’t it a big advantage of—digital—video to be able to record and reproduce motion for 100 percent of the time? 

What do you mean here sir.. ?  100 % of the time..   you mean no shutter ..  it looks like shite generally .. shoot some 25p footage at no shutter .. (1/25th).. it looks really bad.. we only do it when you have no light and clutching at straws .. and even than  a pretty static subject is needed .. even as an "effect" IMHO it just has a really bad look..nothing wrong with shooting digital at 180 degree shutter .. it looks fine.. why not ?

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There is a level at which increasing shutter period doesn't really increase exposure anyway. Some of the worst "360-degree" (which often means close-to-360-degree) shutter is handheld, and all you're really doing is making the motion blur longer, not brighter.

In my view it looks very video.

The only reason we like 180-degree shutter is habituation, but that's enough, isn't it?

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You’re both right.

Handheld camera is nothing I discuss because the best floating cinema moments are made with heavy cameras. The lighter equipment has become the plumper the images looked. I’m just right away bored with mom-and-pop smartphone and digicam imagery. We have too much of that. Of course, some of it is nice.

Nobody said 100 % cycle time looks better than 50 %. I do know that a longer exposure time can be valuable in poor lighting conditions, say under water, in a cave, in the night. Shutter angles should be chosen by the movements we record. Summer holiday sun-beach-fun cameras have 140 degrees shutters, 135 degrees, I could give a list. Those with a variable shutter allow to adapt down to zero, perfect for sports, animals, any fast action. Why not extend to 345.6 degrees with slow moving objects?

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