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Projecting HDCAM


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#1 Eugene Lehnert

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Posted 17 January 2007 - 08:22 PM

Why don't HD projectors project 23.98 tapes? Why do you need 59.94?

If you have a non-drop frame 59.94 tape will it project properly?

Why does HD use 59.94 instead of 29.97?
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#2 David Mullen ASC

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Posted 17 January 2007 - 09:58 PM

If you are referring to some film festival requirements for a 60i HDCAM copy for digital projection, it has little to do with being able to project different frame rates (some HD projectors can handle that) and almost everything to do with only giving the projectionist one format to deal with for multiple movies being screened.

59.94 is interlaced-scan field rate (59.94i), 29.97 is the frame rate -- or it refers to 29.97P (progressive-scan). There are two fields for every frame.
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#3 Eugene Lehnert

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Posted 17 January 2007 - 11:12 PM

Why is 59.94 used by some people and 29.97 used be others?

For instance I set 59.94 as the rate on the HDCAM deck but Final Cut Pro only has the 29.97 option for 1080 and then 59.94 for 720.

Edited by Eugene Lehnert, 17 January 2007 - 11:12 PM.

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#4 David Mullen ASC

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Posted 17 January 2007 - 11:38 PM

Why is 59.94 used by some people and 29.97 used be others?


You need to start putting "i" or "P" at the end of your numbers to be more specific.

Are you asking why some people shoot at 59.94i instead of 29.97P?

If you're asking why material shot at 23.98P or 29.97P is often mastered or copied to 59.94i, it's because in the U.S., HDTV broadcast is either 720/60P or 1080/60i (and when I say "60" I mean "59.94".) So in the case of 23.98P material, a pulldown gets added to convert to 59.94i, just as when 24 fps film material is transferred to 59.94i (and first it is run at 23.976 fps).

If you're asking why 59.94i instead of 60i, it's to make it easier to make NTSC versions, which is 59.94i.

But if you shoot at 23.98P or 29.97P, then you'd probably finish & master to the same format and then make a separate HD master that is 59.94i for broadcast purposes (the "P" version can be used for other applications.)

I can't answer why your FCP software can't handle or convert to 59.94i/1080, but it probably should if it can handle HD.
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#5 Eugene Lehnert

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Posted 18 January 2007 - 04:40 PM

Ok, let me see if I understand this correctly. When something is shot 59.94i that is 59.94 fields shot in a second? NOT progressive frames. If the footage originated in 59.94i each field then has motion that changes from field to field? Which is different than if you shot film at 23.98 added pulldown and converted 23.98 footage to 59.94i? The motion in each field then changes with a 2:3 cadence? When footage is shot 29.97p you can then transfer it to 59.94i with a 2:2 cadence? And broadcasters choose to broadcast in 60p or 60i to because you can convert most formats to 60p or 60i?

What is the difference then between 29.97i and 59.94i? I always thought of 29.97 as frames per second with two fields in each frame. Does the "i" automatically tell you that motion changes from field to field? And the "p" tell you that the motion changes from frame to frame?
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#6 David Mullen ASC

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Posted 18 January 2007 - 08:36 PM

What is the difference then between 29.97i and 59.94i? I always thought of 29.97 as frames per second with two fields in each frame. Does the "i" automatically tell you that motion changes from field to field? And the "p" tell you that the motion changes from frame to frame?


There is no difference -- some people refer to 59.94i as "29.97i" even though that's confusing. "i" should refer to the interlaced-scan field rate and "P" refer to the progressive-scan frame rate. But sometimes 60i is called 30i even though they mean the same thing. However, 60P and 30P are very different things.

Different frame and field rates can be converted to 720/60P or 1080/60i for broadcast. If you shoot 24P or 24 fps film, then you'd use a pulldown scheme to convert 24 frames into 60 fields, because merely splitting them into fields would only give you 48 fields, so you need to insert 12 redundant fields in a pattern to make them less noticeable.

In true interlaced-scan capture, each field is a new "slice" of a moving reality.
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#7 Eugene Lehnert

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Posted 18 January 2007 - 09:29 PM

Ok so that helps clear things up. Knowing for sure now that 59.94i is the same thing as 29.97i is very helpfull.

60p is 60 full progressive frames per second? So then it's played back at 60fps? So that must cut down on motion blur. Then 59.94i is half the temporal resolution of 60p?

Now on an HDCAM deck I have multiple frame rates to choose from. The 29.97 must be progressive then since there is a 59.94 frame rate as well?

Thanks for taking the time to explain this all.
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