jagatai
New member
Okay, I know this is an old thread but this is an issue close to my heart and I actually know a thing or two about it...
I’m pretty sure shutter speed has little or nothing to do with the visual quality difference between 24 and 30 fps. Interlacing has an effect, but it is quite subtle and is not the issue here.
The difference is due to the amount of motion expected versus perceived between frames. 30fps imagery is smoother looking because a moving object moves less between successive frames than it does in 24 fps imagery. Either one is a perfectly acceptable way to capture motion and you should be free to use the frame rate that best appeals to you. But there are very distinct differences in the “quality of motion” and that is a valid consideration when making creative choices.
I have worked in video production in NTSC, PAL and HD for many years. There are very distinct differences in the look of each format. Living in the U.S., I am most familiar with NTSC and 24fps material. NTSC has a reasonably smooth look to it. By comparison, 25fps PAL tends to look very “flickery” to my eye. When I worked at duplicating video tapes and converting to and from PAL, we commonly referred to the look of PAL as having “PAL flicker” 24fps film and HD look “strobby” rather than flickery. It took me probably about a month before I got used to the look of Blu Ray discs that were mastered in 24p. They look strobby in a way that 24fps film transferred to 30fps video with a 3:2 pull down does not. The 3:2 pull down tends to smooth out motion between frames giving a slightly nicer look. You can think of 3:2 pulldown as adding a 1 frame lap dissolve at every 4th frame. Once you know what to look for, it is very hard not to see the difference in motion quality.
But that is just an issue of taste. Some like to motion quality of 24p others prefer 30. There is nothing wrong with either.
On the issue of intercutting 30fps material with 24fps, there are some distinct issues. While it is fairly easy to “upsample” 24fps material to 30fps by adding a 3:2 pulldown, there is no clean way to downsample 30fps material to 24fps unless you use a processor intensive technology such as optical flow to interpolate new frames in between existing frames (I know that this seems counter intuitive since are reducing the number of frames per second, but trust me, it’s an issue.) The problem is to down sample 30fps material to 24fps, you have to throw away 6 frames per second. If you simply throw away every 5th frame, the resulting material has a stuttery look. A smooth dolly shot will have a subtle, but annoying lurch many times per second.
The company I work for transitioned to shooting HD for their industrial film productions. At first, since they were familiar with 30fps NTSC, they continued to shoot at 30fps. But for their own reasons, they soon switched to shooting at 24fps. The result is that every now and then we have to use some of this old 30fps HD in a 24fps project. Luckily it is usually MOS beauty shots where the exact speed that the shot plays at is not particularly critical. I had first attempted to simply downsample the 30fps material, but got the results I have mentioned above. But I discovered that I could simply play the video back at 24fps rather than 30fps minus every 5th frame and I would end up with a shot that looked more fluid (due to the slight slowdown of the motion) and I also had material that cut cleanly into the 24fps project.
Another reason, and this just comes out of the fact that I am extraordinarily lazy, is that from a visual effects standpoint, if I have to work on a shot that runs at 30fps rather than 24fps, that means I have to deal with 6 extra frames for every second of material. For anyone who has every done rotoscoping, you will immediately understand why I would rather work at 24fps. Visual effects can require a lot of work on a frame by frame basis. The less frames you have to deal with per second, the faster you can get through the material.
Also one thing about animators. They tend to learn how motion should look and feel at a particular frame rate. If they learn to animate at 24fps, it will be harder to translate that knowledge of motion to 30fps. While this is less of a problem with animation software that does the in-betweening for you, it still applies to getting just the right cadence and sense of motion when you are setting up a character move that needs to express a very precise emotion or attitude and needs to play back realistically at full speed.
To the average person who is just shooting footage and is not much concerned about technical details or is not especially sensitive to the subtleties of quality of motion, it doesn’t much matter what frame rate you work at. But to those of us who are, the difference can be as grating as fingernails on a blackboard.
Lars
I’m pretty sure shutter speed has little or nothing to do with the visual quality difference between 24 and 30 fps. Interlacing has an effect, but it is quite subtle and is not the issue here.
The difference is due to the amount of motion expected versus perceived between frames. 30fps imagery is smoother looking because a moving object moves less between successive frames than it does in 24 fps imagery. Either one is a perfectly acceptable way to capture motion and you should be free to use the frame rate that best appeals to you. But there are very distinct differences in the “quality of motion” and that is a valid consideration when making creative choices.
I have worked in video production in NTSC, PAL and HD for many years. There are very distinct differences in the look of each format. Living in the U.S., I am most familiar with NTSC and 24fps material. NTSC has a reasonably smooth look to it. By comparison, 25fps PAL tends to look very “flickery” to my eye. When I worked at duplicating video tapes and converting to and from PAL, we commonly referred to the look of PAL as having “PAL flicker” 24fps film and HD look “strobby” rather than flickery. It took me probably about a month before I got used to the look of Blu Ray discs that were mastered in 24p. They look strobby in a way that 24fps film transferred to 30fps video with a 3:2 pull down does not. The 3:2 pull down tends to smooth out motion between frames giving a slightly nicer look. You can think of 3:2 pulldown as adding a 1 frame lap dissolve at every 4th frame. Once you know what to look for, it is very hard not to see the difference in motion quality.
But that is just an issue of taste. Some like to motion quality of 24p others prefer 30. There is nothing wrong with either.
On the issue of intercutting 30fps material with 24fps, there are some distinct issues. While it is fairly easy to “upsample” 24fps material to 30fps by adding a 3:2 pulldown, there is no clean way to downsample 30fps material to 24fps unless you use a processor intensive technology such as optical flow to interpolate new frames in between existing frames (I know that this seems counter intuitive since are reducing the number of frames per second, but trust me, it’s an issue.) The problem is to down sample 30fps material to 24fps, you have to throw away 6 frames per second. If you simply throw away every 5th frame, the resulting material has a stuttery look. A smooth dolly shot will have a subtle, but annoying lurch many times per second.
The company I work for transitioned to shooting HD for their industrial film productions. At first, since they were familiar with 30fps NTSC, they continued to shoot at 30fps. But for their own reasons, they soon switched to shooting at 24fps. The result is that every now and then we have to use some of this old 30fps HD in a 24fps project. Luckily it is usually MOS beauty shots where the exact speed that the shot plays at is not particularly critical. I had first attempted to simply downsample the 30fps material, but got the results I have mentioned above. But I discovered that I could simply play the video back at 24fps rather than 30fps minus every 5th frame and I would end up with a shot that looked more fluid (due to the slight slowdown of the motion) and I also had material that cut cleanly into the 24fps project.
Another reason, and this just comes out of the fact that I am extraordinarily lazy, is that from a visual effects standpoint, if I have to work on a shot that runs at 30fps rather than 24fps, that means I have to deal with 6 extra frames for every second of material. For anyone who has every done rotoscoping, you will immediately understand why I would rather work at 24fps. Visual effects can require a lot of work on a frame by frame basis. The less frames you have to deal with per second, the faster you can get through the material.
Also one thing about animators. They tend to learn how motion should look and feel at a particular frame rate. If they learn to animate at 24fps, it will be harder to translate that knowledge of motion to 30fps. While this is less of a problem with animation software that does the in-betweening for you, it still applies to getting just the right cadence and sense of motion when you are setting up a character move that needs to express a very precise emotion or attitude and needs to play back realistically at full speed.
To the average person who is just shooting footage and is not much concerned about technical details or is not especially sensitive to the subtleties of quality of motion, it doesn’t much matter what frame rate you work at. But to those of us who are, the difference can be as grating as fingernails on a blackboard.
Lars
