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XDCAM HD resolution drop

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Tip McPartland
XDCAM HD resolution drop
on Oct 20, 2006 at 8:39:54 pm

I know that when using overcranking, above certain frame rates (or is below certain shutter speeds), the 350 will lose half its vertical resolution from 1080 to 540. I've read that this occurs at frame rates over 25 fps. This post was from someone very knowledgable, as I recall Simon Wyndham (spelling?) who lives in PAL land, so I wonder if perhaps 30 fps is still full rez? I know its a world cam so his camera would include NTSC-type frame rates too. So that makes me concerned that 30P is hobbled.

But does this just apply to the overcrank function, and so it doesn't affect "normal" 30P or 60i recording? Or is there really no difference, 30 fps is 30 fps, overcranked, undercranked or whatever so the rez drops.

Can anyone clarify this situation for me, because for some of my shooting 30P is ideal rather than 24P, but not if it costs me 540 lines of vertical resolution. Then I'm a 24P man all the way.

Tip


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Nate Weaver
Re: XDCAM HD resolution drop
on Oct 20, 2006 at 11:23:15 pm

Hey Tip,

I was in on the Texas camera tests in April with Adam Wilt where we looked at this stuff.

30p is full res. 31fps is not. Also, don't confuse the half-VRes overcrank modes with what happens to the vertical resolution in 24p mode. In overcrank, the camera actually writes 1440x540 MPEG files to disk...but in 24p (with shutter on), you lose about 10-15% vertical res. I can see it on a chart (and even then it's a little hard to see), but in real life I don't miss it at all.


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Tip McPartland
Re: XDCAM HD resolution drop
on Oct 21, 2006 at 5:11:19 am

Hey Nate,

Thanks for your post. My mind is to some extent put to ease knowing that 30P is good, but who would've thunk that they screwed up 24P even by that percentage. Do you know why that happens? If 15%, that would bring the camera down to 918, still a bump up from the JVC but will probably go fuzzy on the newer 1080 line TVs. Anyway, gracias for the info.

If you're in Santa Monica or West LA, call my office at 310 806-4406 and I'll pop for lunch.

Tip


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Nate Weaver
Re: XDCAM HD resolution drop
on Oct 21, 2006 at 6:36:31 am

The party line on why the 24p resolution is lower is because the camera is making 24fps from interlaced CCDs, most likely running at 48hz. It no way half resolution though, Sony has some secret sauce going on.

Also be aware that just because a set of CCDs are say, 1080-line, there's something called the Kell factor that keeps them from resolving 1080 lines. Kell factor, from what I know, is generally 70-80% of pixel resolution, depending on who you ask. There's lots of things at work to lower the end resolution of a camera...I like to think of the 350 as delivering 800+ lines V and H.

Just FYI, I picked this all up from working by Adam Wilt's side for 4 days of camera testing, both in January and April.

I wouldn't sweat it. It's a great camera for the money...


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