Can someone explain Variable Frame Rates to me?

P

ProAmateur

Active member
I know this is a really noob question, but given my amateur status, I have only been shooting with DSLRs and HMC150s...none of which have vfr. I therefore have no experience with it.

Do I understand correctly that they allow slow motion and fast motion to be done better and more easily? For example, if you are shooting in 1920x1080 30p and dial in a higher frame rate (say 60) that clip will them be able to be dropped into a 1920x1080 30p timeline and be slow motion when played at normal 100 percent speed? Am I understanding this correctly?

If so, what is the difference between that and when I hear people saying they recorded at 60p then just dropped it into a 24p or 30p timeline? I never really understood that whole thing either. If you shot mostly 1920x1080 24p or 30p and are editing in a 1920x1080 24p or 30p timeline, how do you drop in a 1280x720 60p clip? Will that clip not fill the screen because of the 1280x720 resolution?

Then there is the whole thing about taking a 60p clip and converting it to 24p or 30p with Cinema Tools. How is that different from any of the above?

I know, I know, pretty basic stuff right? But for some reason thus far, these things have escaped me and what I have been shooting/doing. Thanks for any help.

Regards,

G.
 
You are right.

The first thing, with VFR it becomes native frame rate in playback. Say your native is 24p and you shoot 60fps, it plays back in 24 in the camera and in your editing.

Its that easy. What others do is the record 60 native then haft change it down to 24p in post.

That 720p clip will not fill the 1080p timeline. AF100 is first with 1080p VFR.

Hope that helped
 
Thanks that does help me to feel better about how I "thought" the whole thing worked.

When you say the AF100 if first with 1080p VFR, I assume you are excluding the HPX170 because its not "true" 1080p?

Oh yea one more thing...what makes it better or worse, to convert a 60p clip with Cinema Tools versus dropping a 60p clip into a 30p time line or even simply playing (within the timeline) a 60p clip back at 50 percent speed? Seems like I read somewhere that it became an issue of your timeline simply dropping every other frame?

Regards,

G.
 
If we record say at 1080/60p VFR, is the data recorded onto the SD card at 2x24mbit=48mbit/sec? How would that be in line with the AVC standard?
 
nugat said:
If we record say at 1080/60p VFR, is the data recorded onto the SD card at 2x24mbit=48mbit/sec? How would that be in line with the AVC standard?
Click to expand...
It gets recorded at a higher bitrate, not exactly double; at 1080/60 the data rate is about 35mbps.

It still complies with the AVCHD standard because that amount of data is recorded in realtime, but less of it gets played back during playback. If you shot in 1080/30p mode at 60fps for one second, it would take up 35mbps. But it would be recorded for playback in slow-mo, which means the actual recorded file would show that it was two seconds long. Same 35mbps, but divided across two seconds of playback, gives you 17.5mbps, well within the AVCHD standard.
 
Not sure if this has been discussed yet for the AF100 but what should my shutter be if I am shooting at 60FPS?

1/60th? 1/120th?

I am seeing some bad strobing on my camera with the shutter at 180d.
 
>1/60th? 1/120th?

I think 1/120th? Or even faster if you like to slow it down in post.
 
I believe that if you set your shutter to synchro scan in degrees, it will hold throughout over and under crank.
 
In normal cases Motion picture is always expose and play or project in 24 frame per second(1/24).if you want to do slow motion ,you have to shoot higher than normal speed, then play back in normal speed that means ,you have to shoot48 frame per sec.or 60 frame per sec,ore 120 fps,then you play back in normal speed at24 frame per sec,then u will get slow motion,
If u want to do fast motion u have to shoot in lower than normal speed that means 20 frame/sec,or 22 frame/sec then u play back in normal 24fps u will get fast motion
here in AF 100 same thing,if u shoot at 60fps then u play back in 24fps time line u will get slow motion .
so your camera is set on 180degree shutter angle u have to set your shutter speed at double of your frame rate that means if you are shoot at 60fps your shutter should 1/120,if you are shoot at 30fps your shutter speed at 1/60,
Thanks
 
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If you're shooting 720/60p for the "live" look (like sports or news) use 1/60th.
If you're shooting 1080 @ 60p for slow-mo purposes, use 1/120th.
 
BollingerPro said:
Not sure if this has been discussed yet for the AF100 but what should my shutter be if I am shooting at 60FPS?

1/60th? 1/120th?

I am seeing some bad strobing on my camera with the shutter at 180d.
Click to expand...

Always 2X your frame rate, so 1/120... unless you want more motion blur (so <1/120), or more stuttered/strobed motion (so >1/120).
 
BollingerPro said:
Not sure if this has been discussed yet for the AF100 but what should my shutter be if I am shooting at 60FPS?

1/60th? 1/120th?

I am seeing some bad strobing on my camera with the shutter at 180d.
Click to expand...

This question worthy of a series of tests in its own right. Certainly its one I will undertake for my self anyway.

Reason is. Under and over cranking on a digital camera is somewhat different to a motion picture film camera ( which is mechanical).

Note: Effect of camera speed changes depend on many things. eg velocity and size of subject. Vertical or horizontal movement thru frame , proximity to the lens, lens fov, camera movement (tracking subject) etc...

BTW : its a good idea to factor the fps x2 of the shutter speed. Thats what a film camera does automatically
 
So if I'm shooting at 1080/30p with a frame rate of 60 for overcrank I should then set my shutter to 1/120th. Correct?
 
If you want it to emulate the exposure and motion characteristics of movie film from a movie camera with a 180-degree shutter, then yes.
 
D10S said:
So if I'm shooting at 1080/30p with a frame rate of 60 for overcrank I should then set my shutter to 1/120th. Correct?
Click to expand...

And just so you know why you are doing this.

A 1/60th of a second is a relatively slow shutter speed ( especially in still photography terms where 1/125+ is more normal for sharp imaging).

1/48, 1/50 and 1/60 barely freezes motion and generally contains a degree of motion blur. You dont want motion blur in slo mo footage because it is more pronounced. The higher shutter speed works towards "freezing" the motion in each frame and reducing motion blur.
 
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