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HPX900 System Mode


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#1 Stephen Price

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Posted 06 June 2008 - 01:52 PM

Hi Guys,

I'm a little confused about how the HPX900 system mode works, I've searched the forums and cant find the specific answer i'm looking for...

When wanting to shoot 1080 25p on this camera, do you choose System Mode 1080-50i, then select Camera Mode 25P?

If so, why is that? It it true 25p? What does '25p Over 50i' mean?

And one other question, for shooting 25p, what should the time code display select be set to? Why is the only two options, 30F and 24F? Which should i put it to, when wanting to shoot 1080 25p in the UK.

Thanks so much

Steve Price
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#2 Andrew McCarrick

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Posted 06 June 2008 - 02:04 PM

Hi Guys,

I'm a little confused about how the HPX900 system mode works, I've searched the forums and cant find the specific answer i'm looking for...

When wanting to shoot 1080 25p on this camera, do you choose System Mode 1080-50i, then select Camera Mode 25P?

If so, why is that? It it true 25p? What does '25p Over 50i' mean?

And one other question, for shooting 25p, what should the time code display select be set to? Why is the only two options, 30F and 24F? Which should i put it to, when wanting to shoot 1080 25p in the UK.

Thanks so much

Steve Price


I don't know about the timecode thing, but 25p over 50i, means the camera scans 25 progressive frames (whole frames) and then divides up each frame into 2 frames with half the amount of lines.
So it scans frame 1, and then places the odd lines (1, 3, 5, 7, 9, ect.) into recorded frame 1, and the even lines (2, 4, 6, 8, 10, ect.) into recorded frame 2. And that continues to get the 25 frames into 50 interlaced (half) frames.

Then in post you deinterlace to recombine those interlaced frames into whole frames. And yes, you'd choose the 50i system option, then the 25p option.

Edited by Andrew McCarrick, 06 June 2008 - 02:08 PM.

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#3 Ollie Bartlett

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Posted 06 June 2008 - 02:07 PM

I asked the same question last week... the answers can be found here:

http://www.cinematog...showtopic=31355

and then discussed in further detail here

http://www.cinematog...showtopic=29642

good luck,

Ollie
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#4 Stephen Price

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Posted 06 June 2008 - 02:14 PM

Thanks so much for your replies!
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#5 Mitch Gross

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Posted 07 June 2008 - 07:36 PM

Best way to think about it are as two different sections to the camera. The first is the camera head, which can be set to scan the sensor at 25 progressive frames each second. The second is the recorder end, which has to actually lay the signal down on tape. DVCPROHD has only two available recording modes: 720p and 1080i. So the only way to lay down the 1080/25p signal is on a 1080/50i recording path. The original signal is a true 25p and remains a true 25p, with the look that goes with a progressive capture.
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