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To 30P or Not To 30P?
Lately in our high-end productions, we’ve been using our Varicam in 30P mode. The resulting look is more “film” like, especially with motion.
But there are issues that I’m starting to notice when I have to perform an effect on the 30P footage.
Namely, chroma keying.
If a person in front of a blue screen doesn’t make sudden movements, the key is fine. But any faster motion with their hands or a small prop, the keyer is having a hard time defining the edges in the motion.
It’s almost like the motion is so blurred, that it “disappears.” Of course, the keyer does it’s job, but it often ends up that the talent’s hands or fingertips are “gone,” or keyed-out, because there just isn’t any information–due to the motion–to key properly.
Other issues I’m seeing are fast horizontal motion. If a subject runs across the screen, and the camera is stationary, the result is so blurred that it’s hard to look at or to see any definition.
So, I ask this. Are we using 30P for the wrong reasons? If so, WHEN would you want to shoot in 30P?
It should be noted that, at least for the foreseeable future, that while we shoot in HD with our Varicam, we do not edit in HD. There’s just no need in our market for HD end-products.
Thanks for your input.
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James Orlowski
RYNO Production, Inc.
http://www.rynoproduction.com
800-860-7966 -
8 Replies
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Can you tell the cow what shutter you were using?
Ray Palmer, Engineer
Salt River Project
Phoenix, AZ
602-236-8224 office
There are three types of people in this world, those that can count and those that can’t. -
I’m not the shooter. I post what others shoot. So I don’t know off-hand what was used. I can ask next time I see them.
If I had to guess, I’d say they didn’t use any special shutter settings.
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James Orlowski
RYNO Production, Inc.
http://www.rynoproduction.com
800-860-7966 -
James,
Ray has the right idea; when you shoot at 30p (aka 30fps) you must always invokea shutter of half or 180 degrees to yield a shutter speed of 1/60th of a second to recreate “normal” motion artifacts as might expect at 24p with a 180 shutter or at 60p with shutter off.
Without turning the shutter on at 30p, you’re getting a default shutter speed of 1/30th of a second which will reveal quite a bit of motion blur when you look at indivifual frames, as your keyer is doing!
JS
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Thanks for the tip. I’ll pass this on to our shooters.
I’m a little confused about the 180-degree shutter rule you mentioned.
Standard 60i shooting with no shutter on is really shooting with a shutter of 1/60, right?
So, if we shoot 30P, what should the shutter be set to? And, will this change the overall “look” of the video, thus rendering shooting in 30P “useless”? (i.e., might as well shoot 60i?)
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James Orlowski
RYNO Production, Inc.
http://www.rynoproduction.com
800-860-7966 -
Yes, 60p with shutter off is 1/60th of a second. 30p with shutter on and set to 180 degrees (half shutter) is 1/60th of a second. The two will look completely different, even though the shutter speeds are the same; at 60p there are 60 slices of action per second, yielding a live or video look, at 30p there are thirty slices of two-frame groups per second, yielding a more filmic look.
JS
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Thanks. This is very helpful.
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James Orlowski
RYNO Production, Inc.
http://www.rynoproduction.com
800-860-7966 -
[jamski] “It should be noted that, at least for the foreseeable future, that while we shoot in HD with our Varicam, we do not edit in HD. There’s just no need in our market for HD end-products. “
So what form of SD are you cutting and keying in? This could also have an effect on how good of a key you can get. For instance if you capture your varicam footage to a 10bit uncompressed SD codec you will get better keys that if you captured to a DV NTSC codec.
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Actually, if there’s a particularly “tricky” key or effect I’m working on for a particular shot, I *do* grab the shot in HD (720p) mode, so I can work on the clip better.
But, for the most part, we grab via SDI in at 720×486 resolution via our Xena LH cards.
Thanks.
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James Orlowski
RYNO Production, Inc.
http://www.rynoproduction.com
800-860-7966
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