Faster shutter or faster shutter and more frames?

MartinE wrote on 5/19/2016, 7:00 AM

OK I normally shoot 1080p 25fps 1/50s shutter. I edit in VP13 1080p 25fps and render AVC mp4 1080p for upload to Youtube. This works great for most stuff. However if I want less motion blur on pans and for fast moving subjects (not necessarily for slow motion), the current wisdom seems to be to shoot say 50fps (1/100s) ie each frame is sharper. However why don't I just shoot 25fps at 1/100s in the first place since in the edit I'm going to lose the extra frames anyway and deliver 25fps. Put another way how do the extra frames help me or maybe Vegas is doing things with these extra frames that I don't understand. I hope this makes sense. I know it's a frequent question but I just want to get to the bottom of it.

Many thanks in advance.

Comments

riredale wrote on 5/22/2016, 4:12 PM

You're right, two different questions.

Frame rate for film has traditionally been 24Hz, and people tolerate it because cameramen and directors know that any fast pans will result in groans from the audience. So they've learned to work within those limitations.

25Hz should be about the same, but if you shoot at 50 you have the option of doing other things with your footage down the road. Much of what you see on TV is done at 50 or 60 because it was shot interlaced.

As for shutter speed, a slow speed blurs motion and a fast speed sharpens it. Personally I hate the bop-bop-bop strobe effect of a high shutter speed, and again I think people have gotten used to the motion blur from a slow shutter. But experiment and see what you think.

As a private pilot I enjoy viewing YouTube videos of propeller-planes but it drives me nuts when the shooter either obliviously or intentionally uses a super-fast shutter speed. Very unnerving to me so see the individual blades stationary or turning slowly (even backwards!) with the engine running. So blur can be a good thing.

Former user wrote on 5/22/2016, 9:31 PM

"Much of what you see on TV is done at 50 or 60 because it was shot interlaced."

I think you meant to say that most TV is 25fps or 30fps because it is interlaced.
(50 fields or 60 fields)

OldSmoke wrote on 5/22/2016, 10:28 PM

I always think of 60i as 60 frames with half the lines/information but it is still 60 frames a second and not 30; but I could be completely wrong.

As for the OPs question, if you have a fast moving object and shoot 25fps at 1/100 than each frame will be sharper but it will have the strobe look because you are missing a lot of temporal information and there is little motion blur. Shooting at 50p would make it very smooth but only if you play it back at 50p. YouTube already does 50p and most TVs too but not DVD; BluRay may soon do it too as the spec is being worked on.

Former user wrote on 5/22/2016, 10:39 PM

60i is 30fps. They called it 60i to differentiate from SD. Each frame is made up of 2 fields, thus 60fields per second interlaced-60i

OldSmoke wrote on 5/23/2016, 12:41 PM

Donald.

You are correct. However, the camera still records 60 frames per second but only half of the lines. While you may say only all lines make one frame, it is not displayed as 30 frames on the TV. Every 1/60sec you see either the odd or even lines but never both together on a CRT display. There is however a 30PFS which is an actual 30p but can not be displayed by CRT displays. In this case, there is no temporal different between the two fields, it's just the same frame split over two fields by separating the even and odd lines.
How does it differentiate from SD? SD is 720x480 60i, exactly what you would render for a DVD.

riredale wrote on 5/23/2016, 3:17 PM

The point I was clumsily trying to make in my original response is that traditional 60i may not have all the scan lines 60 times a second but it does contain fully half of them and that format shows a temporal resolution of 60 images per second, which can matter a lot for scenes with heavy motion.

Former user wrote on 5/23/2016, 4:08 PM

OldSmoke, that is the same as 29.97 interlaced. Each frame consists of 2 fields displayed consecutively. Odd/Even lines. So it is only 29.97 frames per second, or 59.xx fields per second. Always has been. But yes, it is 60 unique images at half resolution.

The only time you get a full 60 frames per second is progressive.

Standard definition is just a difference in resolution, the math is the same.

Yes, Riredale. Action is a a bit smoother with interlaced because your eye perceives the differences in fields as a more fluid motion.

Rory Cooper wrote on 5/24/2016, 4:01 AM

Just to clarify the real issue.

The 25 fps is one issue and shutter speed is a separate issue. you cannot solve one problem with another problem you will simply now have two problems.

25 p frames or 50 p frames will not solve the shutter motion issue or problem.
Shooting 50 frames slowing and rendering to 25 fps will give you audio problems and motion problems they will not sync and you will have slo motion

You need to manage the issue of 25fps
One way is by filming motion toward or away from you and not side on.
For pan judder is to bring the camera slightly forward off dead centre with your tripod using rails etc so the pan is an arc and not a tight turn or get a motorised pan head.

Interlacing issues will not solve 25 frame issue.

50i is the same as 25p in images frames 50i is not more than 25p. If I have a loaf of bread cut that into 25 slices = 1 progressive loaf. Now I cut those slices in half again and get 50 half slices = Interlaced loaf I still only have one loaf. So interlaced cannot solve the motion issue simply blur it a bit. Interlacing was developed for broadcasting and is a bandwidth shortcut/money solver but an editors nightmare. So film progressive and watch your angles.

OldSmoke wrote on 5/24/2016, 7:28 AM

But yes, it is 60 unique images at half resolution.

Exactly my point. 60i is 60p with half the lines. Take a 60p clip into Vegas and render it out to 60i and it will be perfect 60i because Vegas will simply drop every odd and even line. Try the same with 30p and all you get is 30 frames progressive scan. The first frame/field will have the even lines and the second will have the odd lines from the same frame. The only difference between SD (720x480 60i) and HD (1920x1080 60i) is the number of pixels. Full HD, 1920x1080 60p (59.94) or 1st gen HD 1280x720 60p is full progressive. I still feel it is wrong to call 60i 29.97 frames because that is not what it is, because as you also pointed out 60i has unique 60 half frames.

Anyways, I am not helping the OP with my argument and yes, interlaced has smoother motion. How about reading it?

Former user wrote on 5/24/2016, 7:40 AM

sorry, yes we are not answering the original question

"I still feel it is wrong to call 60i 29.97 frames because that is not what it is, because as you also pointed out 60i has unique 60 half frames."

We are saying the same thing and although you feel it is wrong, technically it is correct. As even the article you linked to talks about frames vs. fields.