...continued from Producer's Cheat Sheet September 2009.

Progressive vs. Interlaced Continued

What to expect... For most shooters, not experienced in shooting in progressive modes, there is a complaint about flickering and jittery or un-sharp images compared to interlaced footage. Interlaced footage has problems of its own including ‘ line twitter’ and ‘interlace tearing’. For example, when wearing a shirt with fine dark and light stripes on TV, these stripes would appear to be ‘twittering’.
So, why do all those movies shot on film or progressive modes look great at the theater and don’t have the so-called ‘judder’ or ‘flicker/strobe’ effects that your progressive camcorder seems to have? The simple answer is because production companies hire a professional DoP (Director of Photography) and pay him/her to get it right. The DoP knows exactly how to ‘Block and Stage’ every shot in such a way that prevents any judder or flicker in the final footage. This means smooth, slow and steady shots. The exceptions are films such as Bourne Identity, Saving Private Ryan, Band of Brothers and many other shots in big movies. The problem of judder usually happens with medium speed objects. Slow movement and faster movement doesn't suffer .The fact of the matter is that once the eye starts watching progressive footage, it will fill in the blanks; this is known as persistence of vision.

The solution... When shooting with a camcorder with progressive mode, it is important to follow the action. If you were to lock-off your camera and set the zoom to medium/wide in a crowd and film an actor walk past, in progressive mode the actor would enter the frame, then ‘judder’ or ‘flicker’his way across the frame, and finally leave the frame. Instead of locking the camera off on a tripod, you would carry out a panning shot instead; panning the actor as he walked past. Following the actor, the people behind him would now be moving across the frame, and they would start to ‘judder’ instead. So, to alleviate this problem of background-judder, you would adjust the camcorder’s aperture by opening it up to make the depth of field shallower, hence knocking the background out of focus slightly. Making the background slightly out of focus will hide the fact that they are ‘juddering’ across the frame and the end result will be beautifully crafted footage that has a crisp progressive look. However, at the distance you would need to be to follow the actor with a pan, the background will probably be moving too fast to have any noticeable judder. Furthermore, the human eye will ignore the judder because it will be focusing on the object of interest. Compose the shot and follow the object of interest. Keep wide shots steady; people do not walk across the frame, but are followed into, and out of it.
When shooting in progressive mode don’t forget to turn the shutter on and set it to 1/48th. This is the equivalent of a ‘double gate’ effect of a projector i.e. sharpening up the look of the footage. With no shutter the footage will have a slight ‘blur’ about it. Shooting in progressive mode will also give more of a ‘film look’, which is ideal for creative productions.
As a progressively shot frame is one complete/whole frame (just like a picture taken on a digital stills SLR camera) it is easy to take a frame grab off the timeline and import it into a photo manipulation program like Photoshop and print it out or publish it as a still photo on the web. Because the still is free of interlacing lines it will be crisp and clear with zero interlace ‘tearing’.

The advantages of shooting progressive are great. For example, if you are a low-budget independent filmmaker it’s much easier to do a digital transfer to film if the footage was shot progressively to start with. Shooting progressive is also a good way to ‘future-proof’ your footage; there is no place for interlace in the future. As already mentioned, taking still frames off the timeline and using them as still pictures is easy. Other advantages are that progressive scan compresses much more efficiently for DVD etc. You can pan, zoom, and crop progressive scan footage far more easily than interlaced footage. For example if you have progressive footage and want to intercut old 4:3 interlace footage, but you want to zoom into the 4:3 stuff to make it 16:9 anamorphic to match the rest of the program; interlace shot footage will cause havoc.

Return to Producer's Cheat Sheet September 2009.

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2009