With 60P video, does Vegas use all frames for 30P?

Rich Parry wrote on 4/25/2015, 12:47 AM

I shoot 60P with my Sony AX100, this allows me to slow down motion when necessary without loss of quality assuming I output to 30P.

However, is there is an advantage to shooting 60P if I am not slowing down motion? It seems to me Vegas just throws away every other frame, so I gain nothing shooting 60P. Am I missing something? Does Vegas use all the frames?

I’m not looking for a reason to stop shooting 60P, I just want to understand what Vegas is doing with 60P video. I know when there is a lot of motion 60P is preferred, but it seems it is just a waste of frames if I am rendering to 30P.

If Vegas is using all the frames, I suppose you could even argue you can shoot 120fps when rendering to 30P. In this case is Vegas using 4 frames to make one frame?

Thanks in advance,
Rich

Comments

John_Cline wrote on 4/25/2015, 1:10 AM

If resampling is turned off for the 60p clip, then Vegas will just drop every other frame and it will be no different than if you had shot 30p. If resampling is turned on, then Vegas will blend two frames for each frame at 30p. This may or may not be acceptable, you'll just have to try it.

set wrote on 4/25/2015, 6:13 AM

Resampling 60p to 30p (or 50p to 25p) will create ghosting effect.
Try see it in high-motion clips, and you will notice the difference.

John_Cline wrote on 4/25/2015, 7:03 AM

It will create ghosting only if resampling is turned on for the clip ("on" is the Vegas default.) You can either disable resampling or leave resampling on and set the undersample rate to ".5", either way converts 60p to 30p (or 50p to 25p) without ghosting.

OldSmoke wrote on 4/25/2015, 8:53 AM

I also shoot 60p because it will give me all the options. With 60p you get perfect 30p for Internet, 60i for DVD and BluRay as well as 1280x720 60p for BluRay if you have projects with fast motion.

I wish the AX100 would do 4K 60p but that would also require a much faster machine.

I shoot 60i together with 30p (dual recording) if I quickly need to put a report together which I can do on my iPad with iMovie and upload it to YT or Vimeo. Once home, I use the 60i to upload higher quality or make DVDs, BluRay or others for distribution.

4K 30p is only for my home videos, especially hicking videos, landscapes, anything with less motion looks stunning in 4K 30p.

musicvid10 wrote on 4/25/2015, 8:59 AM

The real advantage of shooting 60p or 120p is stunning 30p Slomo.

Chienworks wrote on 4/25/2015, 9:01 AM

"Surprised nobody mentioned it."

Actually, Rich mentioned it in his first sentence! ;)

CJB wrote on 4/25/2015, 9:05 AM

The disadvantage shooting 60p for 30p is your motion blur is off. There is software that will interpolate between frames but correct motion blur is best in camera. In other words your shutter angle will be half what it should be.

OldSmoke wrote on 4/25/2015, 9:50 AM

dancerchris

Why would it be off? I shoot 30p at 1/60 and I shoot 60p at 1/60 so no difference at all.

CJB wrote on 4/25/2015, 11:04 AM

The OP was suggesting that shooting at 60p gives you the freedom to do 30p and slow motion with nothing to lose.

While it is true shooting 60p at 1/60 sec shutter gives you proper motion blur for 30p normal speed footage, this does not translate to slow motion. If the footage was shot at 60p and you wanted to display all the frames for slow mo with standard motion blur you'd want to shoot at 1/120 sec (180 deg shutter). This would give you non slushy slow mo if displayed at 30 fps. Shooting at 60p at 1/60 sec gives you 360 deg shutter and too much motion blur for displaying all frames (obviously you can go for an "art look"). Look at the OP's argument of going to 120p, if the versatility theory held up you would shoot at what shutter speed? 1/60th is impossible. So you are left with compromises when you select frame rate and shutter angle, when you use it other than as intended.

I am interested to learn if my conclusion is wrong.

c

musicvid10 wrote on 4/25/2015, 12:37 PM

I don't know if your conclusion is wrong, because you lost me halfway through the paragraph.
Here is 60p -> 30p slomo done on a cheap Kodak pocket can; the word "slushy" never came to mind . . .

The frame rate trumps the shutter speed for temporal effect, not the other way around afaict.

OldSmoke wrote on 4/25/2015, 12:46 PM

musicvid beat to it.

Also 60p slowed down to 1/4 doesn't improve with the shutter speed as Vegas will interpolate between the frames and a shorter temporal spacing might actually work better.

CJB wrote on 4/25/2015, 12:56 PM

It is true that temporally the prime factor is fps value. However regarding motion blur, I respectfully disagree; 60p shot at 1/60 sec is 360 degree shutter angle, i.e too much motion blur when played at 30 fps with no dropped frames ala slo mo. When you drop every other frame you end up with regular timespace and 180 deg motion blur. 180 is what our eyes like. 360 is going to make it a bit smeary if there is motion. If its just people standing around, i.e. a wedding you probably won't notice. Sports or action, big effect. JMO.

musicvid10 wrote on 4/25/2015, 1:23 PM

Sorry, Chris, your math is beyond any compelling need to decipher it right now, and I'm still not getting "slushy slomo."
Fairly crisp, actually. Again, this is a little pocket jellocam.

CJB wrote on 4/25/2015, 3:30 PM

hard to tell on youtube. The video seemed stuttery in 30p, but then most of youtube is like that .There is so much artifacting in the footage around the motion blur (what GOP was this?) that it is hard to tell if the motion blur was too much or not. I am seeing odd stuff in the wake of the cars where there should be some motion blurring. The wheels on the cars appeared to be going backward though that is more a function of frame rate than shutter speed . What shutter shutter speed did you record at? I would be surprised if the little auto camera had control of both shutter speed and frame rate in video mode. If it did it automatically the shutter speed could be 2xFPS auto, i.e. 1/120 sec.

musicvid10 wrote on 4/25/2015, 3:47 PM

NVM

TheHappyFriar wrote on 4/25/2015, 8:24 PM

When rendering my 60p gopro video to 30fps slow motion there's no motion blue (I ctrl+drag until it's 50%). When I render it to 30fps w/o slowmotion there is is the "blur" Vegas adds. I didn't like it but if I drop frames then it's much more crisp then if I could manually change the shutter speed. I don't know of a way in Vegas to drop every other frame & have it look like it was recorded @ 30p with realistic motion blur.

So if I want something to look 30p with the proper motion blur then I record @ 30p. This is because I can't adjust the settings on my gopro though. On my HDV camera I can adjust the shutter speed but it only does 29.97 interlaced.