50p shutter speed

[Nima Taheri]

Hi

I'm doing a music video with a lot of motion, dancing, somersaults etc. I want to record in HDVSD50p mode to slow down some of the footage. By searching this forum, 1/100 and 1/250 shutterspeeds are the way to go. Anyone of experience with tests regarding the difference between these two shutterspeeds?

Also, on shots that I know will not be slowed down, like lip-syncs, will it help to go 1/50 (or even lower), so that I don't get that "live" look?

The final result is for broadcast SD PAL.

Thanks

[Jemore Santos]

I would recommend to go for 100 shutters per second to achieve a 180 degree shutter look on film which does great slow more, 250 will give you a judder look.

[Werner Wesp]

Defenately 100 shutter speed. 1/2 slowed down will look like it's originated on 25p with a (standard) 50 shutter speed.

Don't use 50 or less shutter speed, because footage will end up having blurry motion and blurry dancers (if you would want that, you better record in 720 25p and slow it down with interpolating inbetween frames - that'll look about the same... but I guess that's what you're trying to avoid).

[Jemore Santos]

I would say yes to 50 shutter speed, if you want the 180 degree look. If you go over that, you will get judder.

[Richard Hunter]

Originally Posted by Jemore Santos

I would say yes to 50 shutter speed, if you want the 180 degree look. If you go over that, you will get judder.

At 50fps, (which is what Nima is asking about), don't you need 1/100s shutter speed to get 180 degrees?

Richard

[Jemore Santos]

Well if you slow the 50f/s down to 50% which is 25f/s and if you have the 100 shutter speed slowed down to 50% which is 50 shutter speed you get a good slow-mo, now in PAL land we shoot film @25f/s with and the most common shutter angle is 180 degrees be it PAL or NTSC. now that is 50shutter@25f/s or in NTSC 48shutter@24f/s.

So if you are slowing it down to 50% slow-mo then 100 shutter speed is the go.

[Nima Taheri]

So the 50fps at 1/100 shutter for slow-mo. For the no-slow-mo footage, I was thinking that the 1/100@50fps would look too "live" and not very film-like, or doesn't that really make a big difference (between 1/50 and 1/100). The reason why I'm shooting 50p the whole time is that I don't know what part I want to slow down till post production...

[Bill Ravens]

the reason for wanting at least a 180 degree shutter is more because of the nyquist frequency than for stop motion. according to nyquist, any frequency more than half the fundamental harmonic will result in temporal distortions in the sampled data...for example, film of a rotating wheel will appear to be moving in reverse

[Richard Hunter]

Originally Posted by Bill Ravens

the reason for wanting at least a 180 degree shutter is more because of the nyquist frequency than for stop motion. according to nyquist, any frequency more than half the fundamental harmonic will result in temporal distortions in the sampled data...for example, film of a rotating wheel will appear to be moving in reverse

Hi Bill. I don't see the connection between the shutter speed and the sampling rate in this case. For a given frame rate, I thought the backwards motion effect would be related to the rotation speed of the wheel and the number of spokes, rather than the shutter speed. The shutter speed only determines how much motion there is during each sample, i.e. the amount of motion blur.

Richard

[Jemore Santos]

Originally Posted by Nima Taheri

So the 50fps at 1/100 shutter for slow-mo. For the no-slow-mo footage, I was thinking that the 1/100@50fps would look too "live" and not very film-like, or doesn't that really make a big difference (between 1/50 and 1/100). The reason why I'm shooting 50p the whole time is that I don't know what part I want to slow down till post production...

The reason why it looks too live is because you are watching it in real time, 50fps is a "live look" but if you slow it down to 25fps with 50 shutter speed then that is what you want to have as a "film look".

[Bill Ravens]

if you've ever played with a strobe light and a spinning object, you'd notice that the temporal effects are a function of both the rate of rotation and the strobe rate.

[Richard Hunter]

Originally Posted by Bill Ravens

if you've ever played with a strobe light and a spinning object, you'd notice that the temporal effects are a function of both the rate of rotation and the strobe rate.

Hi Bill, yes I'd agree with that. In this case though, the frames per second which is equivalent to the strobe rate, is fixed. The variable we're talking about is the shutter speed which I think does not cause the backwards motion type of effect.

Richard