key question about 24p vs. 60p

Ron Evans · January 1st, 2006, 12:46 PM

There is a difference between what you may be calling strobing and stuttering. Capturing fast motion at 24fps is just not fast enough, period. It will always stutter but if this is played back so that ones eyes see greater than 50flashes per second it will not strobe( if I am understanding you correctly). In the movie theatre the projector has 2 or more blades rotating in front of the lamp and flashes the picture several times before moving on to the next frame. In this way the film does not strobe but it does still stutter because film shot at 24fps is not fast enough ( whatever the shutter speed, to create smooth motion). Think of a lab setup with 24 equally spaced marks across the frame and a ball rolling across the scene in one sec. The film will take 24 frames one at each one of the marks. When played back at 24fps to the observer the ball will jump between each of the marks NOT roll. This is the stutter of film that cannot be removed but can be masked. To make the ball appear to roll frames have to be taken at a rate that matches the human eye brain perception of smooth motion ( above about 50cycles per sec) OR shoot the ball at an angle so that each frame of the ball overlaps to a great extent the previous frame. The eye is again fooled. Which is why most old films had any fast motion at an angle to the field of view. OR the film is shot at high speed ( not 24fps, maybe 120fps ) and then slowed down to get those slow motion crash scenes popular today!!!!!. As I mentioned in an earlier post there is lots of film information governing these angles for different speeds etc.
IF you are shooting wild life shoot at 60p you can always make it look the way you want in post but at least you will get a nice clean sharp original video. You will need to calculated distances moved across the frame when animals are moving at various speeds to decide what other settings you will need to use. That is, how fast does the shutter speed have to be to just freeze the image at 60P. Remember even at 60P the image is still stuttering it just happens to be above the rate at which we humans care about, but if each of these frames is blurred because the shutter speed is too slow the whole image of the moving animal will appear muddy and out of focus compared to the backround. This is assuming the you want the whole image to be sharp.
Ron Evans

January 1st, 2006, 12:46 PM	#16
Ron Evans Inner Circle Join Date: Mar 2003 Location: Ottawa, Ontario, Canada Posts: 4,222	There is a difference between what you may be calling strobing and stuttering. Capturing fast motion at 24fps is just not fast enough, period. It will always stutter but if this is played back so that ones eyes see greater than 50flashes per second it will not strobe( if I am understanding you correctly). In the movie theatre the projector has 2 or more blades rotating in front of the lamp and flashes the picture several times before moving on to the next frame. In this way the film does not strobe but it does still stutter because film shot at 24fps is not fast enough ( whatever the shutter speed, to create smooth motion). Think of a lab setup with 24 equally spaced marks across the frame and a ball rolling across the scene in one sec. The film will take 24 frames one at each one of the marks. When played back at 24fps to the observer the ball will jump between each of the marks NOT roll. This is the stutter of film that cannot be removed but can be masked. To make the ball appear to roll frames have to be taken at a rate that matches the human eye brain perception of smooth motion ( above about 50cycles per sec) OR shoot the ball at an angle so that each frame of the ball overlaps to a great extent the previous frame. The eye is again fooled. Which is why most old films had any fast motion at an angle to the field of view. OR the film is shot at high speed ( not 24fps, maybe 120fps ) and then slowed down to get those slow motion crash scenes popular today!!!!!. As I mentioned in an earlier post there is lots of film information governing these angles for different speeds etc. IF you are shooting wild life shoot at 60p you can always make it look the way you want in post but at least you will get a nice clean sharp original video. You will need to calculated distances moved across the frame when animals are moving at various speeds to decide what other settings you will need to use. That is, how fast does the shutter speed have to be to just freeze the image at 60P. Remember even at 60P the image is still stuttering it just happens to be above the rate at which we humans care about, but if each of these frames is blurred because the shutter speed is too slow the whole image of the moving animal will appear muddy and out of focus compared to the backround. This is assuming the you want the whole image to be sharp. Ron Evans