slow motion, should it be shot in 30P or 60i?
- Thread starter mvp1
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Barry_Green
Moderator
Depends on how slow you want the slow motion to play back, and whether you place more emphasis on vertical resolution or on smooth playback.
Search the threads, this has been discussed many, many times. Both methods are appropriate depending on your priorities.
Search the threads, this has been discussed many, many times. Both methods are appropriate depending on your priorities.
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Peter Gaudry
Guest
After going through a lot of this, I will tell you that 30p is not that noticeable. You're better going for 60i if you want it to look slow.
Barry_Green
Moderator
30p gives you a 25% slow-motion effect, when played back in a 24p timeline.
60i gives you a twice-as-slow effect as 30p would.
60i gives you a twice-as-slow effect as 30p would.
Okay I am confused.
Lets say something moves 30 inches in one second.
If I record it at 30p, each frame shows 1 inch of the movement.
If I record it at 60i, each frame shows 1/2 inch of the movement, but it is interlaced. So I end up with 60 half-images. When I re-interlace prior to conversion to 24p, I would only have 30 full images again, each one showing a (interlace blurred) 1 inch of the movement.
I don't see why they would yield different speeds at 24p, unless you were converting 60i to 24i...
Did I express that well enough?
Lets say something moves 30 inches in one second.
If I record it at 30p, each frame shows 1 inch of the movement.
If I record it at 60i, each frame shows 1/2 inch of the movement, but it is interlaced. So I end up with 60 half-images. When I re-interlace prior to conversion to 24p, I would only have 30 full images again, each one showing a (interlace blurred) 1 inch of the movement.
I don't see why they would yield different speeds at 24p, unless you were converting 60i to 24i...
Did I express that well enough?
Jay Rodriguez
Coffee Member
galt said:
I assume you don't have Barry's book nor the DVD. I highly recommend it. :thumbsup:
I'll try my hand at this but I'll use 40 inches as my example.
40 inches per second in movement
40 inches shot in 30p then slowed down = 50 inches in final result slow motion
40 inches shot in 60i then slowed down = about 75 inches in final result slow motion
This is my understanding, soon to be tested.
I think that Barry is saying that if you shoot at 30p and playback in a timeline at 24p, it will slow motion down by 25%.
I would personally shoot 60i then convert the 60 fields to 60 full frames using a post-production filter. Although you loose some resolution, I think it looks better.
I would personally shoot 60i then convert the 60 fields to 60 full frames using a post-production filter. Although you loose some resolution, I think it looks better.
Barry_Green
Moderator
mmm has it correct.
Shooting at 60i, you would then de-interlace the footage by turning each field into its own frame. You don't blend fields together, you interpolate the missing field from the field you have. So it becomes a low-resolution version of 60p. You then play that back at frame-for-frame speed in a 24p timeline, and it means that it takes 2.5 times as long to play back, giving you 2.5x slow motion. The downside is the loss of half your vertical resolution.
Shooting at 60i, you would then de-interlace the footage by turning each field into its own frame. You don't blend fields together, you interpolate the missing field from the field you have. So it becomes a low-resolution version of 60p. You then play that back at frame-for-frame speed in a 24p timeline, and it means that it takes 2.5 times as long to play back, giving you 2.5x slow motion. The downside is the loss of half your vertical resolution.
If you shoot at 60i, you have 60 fields per second (=30 frames). If you slow down to exactly 50% (using velocity envelope), you can play back each field as a frame, resulting in very smooth slow motion because of the 1:1 correspondence between field and frame (but, of course, resolution will be degraded). You will probably have to set deinterlace method to "interpolate", and field order to "progressive" for the field to frame conversion to work properly, but double check this to make sure. Does this make sense?