| |
VK2YPZ > INFO 05.07.02 20:55l 41 Lines 1338 Bytes #999 (0) @ WW
BID : 960318VK2YPZ
Read: DB0FHN GUEST
Subj: Re: G8TZJ > FILM SPEED
Path: DB0FHN<DB0ZWI<DB0CHZ<OK0PKL<OK0PHL<OK0PCC<OM0PBM<RZ6HXA<IK1ZNW<VK2XY<
VK2TGB<VK2IO<VK2WI
Sent: 020630/0825Z @:VK2WI.#SYD.NSW.AUS.OC #:47286 [SYDNEY] FBB7.00g25
From: VK2YPZ@VK2WI.#SYD.NSW.AUS.OC
To : INFO@WW
Warren Kb2VXA asks about 3:2 pulldown.
Coming from the USA, you have probably seent his all your life without
realising it.
Basically, the problem is how to fit 24 frames of film to 30 frames of
television.
Divide the numbers above by six and we get 4 frames of film have to fit
into 5 TV frames, which doesn't work very well. Fortunately Television in
both PAL and NTSC is sent as fields rather than frames.
This gives us 4 frames of film for 10 television fields. We can divide
this again 2 frames of film into 5 television fields.
basically, 1 frame is sent over to fields, while the other frame is sent
over 3 fields.
First film frame - Field 1A, Field 1B
Second film frame - Field 2A, Field 2B, Field 3A
Third film frame - Field 3B, Field 4A
Fourth film frame - Field 4B, Field 5A, Field 5B
Yes, you get a television "frame" made up of a field from 2 different film
frames. If you look at a piece of movie film, you will notice that the
adjacent frames usually are very similar, so most of the time there is no
real problem. Really there is no frame, but a succession of fields (to
reduce flicker), and the differences are small enough to still seem like
smooth motion.
73 - Kevin, VK2YPZ @ VK2WI
Message timed: 18:24 on 2002-Jun-30
Message sent using WinPack V6.80
Read previous mail | Read next mail
| |
