30p and 60i - I'm not satisfied

R

Rev_Jeff

Member
I use the HVX200a, and I'm still asking the million dollar question:
What is the FUNDAMENTAL DIFFERENCE between 30p and 60i over an interlaced stream?
Here's my theory, but I would love for this to be CONFIRMED by an authority on the subject:
30p shoots full frames 30 times per second, then SPLITS them into a 60i stream after the fact, and
60i shoots a field at a time, instead of ever shooting a full frame in the same moment.
For example, if a pitcher is throwing a ball, on the 30p footage you would see his entire arm at a given moment in the footage where both fields for that frame are on screen, but if shot in 60i, there is no such moment. Each field is essentially its own frame, only not a full frame... don't know if I can explain that without images, but I will if necessary...
if you get what I'm saying, am I correct?
I'm a little OCD and this has been driving me nuts, because all I've found for an explanation is "it looks different".
Thanks.
 
Rev Jeff, you are correct.

Another way to put it: 1080/30p = 30 progressive frames per second, at 1920x1080 res.
1080/60i = 60 half-frames per second, at 1920x540 res. Twice as many frames, half the information per frame. But instead of being arranged like top/bottom or left/right, the images alternate on even/odd lines every refresh.
 
To add to this, taking that ball players pitch, in the 30P stream, while each frame would be beautiful, you may notice that there is a bit of stutter in the overall movement, like the movement is not smooth. This is because of the fact that there are only 30 images with which to record the action. In a 60i version the motion would look very smooth. This is why many folks that want to study motion will use 60p in 720 vs. 1080/60i,\; there is just more infor on the vertcal (720 lines vs 540 interlace in the 1080)

Hope this adds,

Jan
 
You must log in or register to reply here.
Back
Top