1080 vs 720p + HVX

J

jdv

Well-known member
I was wondering if anyone could explain exactly what the difference is between shooting at 1080 v 720... Is 1080 interlaced while 7200 is not?

- Apparently the HVX can shoot naitively at 1080 then 'downrez' to 720p.... But what, exactly, does this mean?

-Specifically, what are the ramifications as to an eventual film-out from something shot on the HVX? For a DVD release only?

- I believe if you shoot at 720p, it would take up less drive space on P2 cards/hard drives... Is this correct?

Thanks for the knowlege - John
 
The HVX apparently images everything at progressive 1080/60p, if our interpretation of the babelfish of the Japanese spec sheet is accurate. It then converts the progressive into interlaced if necessary.

1080 can be progressive or interlaced, 720 is always progressive.

1080 has twice as many pixels per frame. That does not mean it records twice as much detail though -- none of the affordable HD cameras can capture anywhere near a full 1920x1080's worth of detail! The JVC HD100 is 720p-only, the Sony Z1 is 1080i-only, and on res charts they both capture about the same amount of detail.

I would expect that the 1080 modes of the HVX will be preferable to the 720 modes for film-out; the 1080 modes will record twice as many pixels, and twice as many chroma pixels, as the 720 mode does. So however much detail is retained in 1080 vs. 720, the 1080 mode will record/keep more of the pure detail than the 720p mode will.

But, the 720p mode can record 60 full progressive images per second, whereas the 1080 mode can't. It can only record 30 progressive images per second, or 60 interlaced fields. So for temporal motion, 720p will be better. For spatial resolution, 1080 will be better.

720p can take advantage of variable frame rates, and it can take up less space on the card (720/24p takes up 40% as much space as 1080/24p does, for example; but 720/60p takes up the same amount of space as 1080/60i does).

For DVD-only, I wouldn't use either HD mode, I'd instead choose DVCPRO50, which will give you 4:2:2 color and much cleaner compression.
 
Barry_Green said:
For DVD-only, I wouldn't use either HD mode, I'd instead choose DVCPRO50, which will give you 4:2:2 color and much cleaner compression.
Click to expand...

Is DVCProHD not 4:2:2 ?
 
alpi69 said:
Is DVCProHD not 4:2:2 ?
Click to expand...

Yes it is. But he refered to MiniDVand DVCPRO25 that is just 4:1:1


But if you shoot for DVD and its something that will last for a while i still would recomend 720P. But that depends on the material.
 
MovieSwede said:
Yes it is. But he refered to MiniDVand DVCPRO25 that is just 4:1:1
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I'm not sure if when Barry says: «much cleaner compression» if he's refering to MiniDv or DVCPRO25, I think maybe «either HD mode» have, in any circumstance, more compression? I ask: noticeable @big screen?
 
Yes DVCPROHD is more compressed than DVCPRO 50.

As for DVCPRO HD noticealbe at big screen. Not likely for a "normal" eye. Sure if you knew what to look for maybe. But how often do you se the compression on minidv? the things thast give away minidv is the overexposure and heavy reds.
 
DVCPRO-HD (DV100) compression is 6.7:1.
DV and DVCPRO compression is 5:1.
DVCPRO50 (DV50) compression is 3.3:1. DV50 is a lot cleaner than either DV or DV100.

If your only purpose in shooting the footage is to make a DVD, I'd expect DV50 to be the best source footage. However, the additional mosquito noise artifacts of DV100 would probably be masked well in a downrez.
 
Barry, et al - besides not being able to shoot slo-mo in 1080, and taking up more space on the p2 card/hard drive, are there any other negitives to shooting in 1080 mode?

Will shooting in 1080 have benefits over 720p for shooting blue/green screen shots? Thanks again for the help...john
 
Depends on how much actual detail is being produced by the chipset.

1080 has twice the spatial resolution of 720. It can record twice as much detail as 720 can. But -- and here's the big question -- is there that much detail in the source signal to begin with? If the 720p mode is capable of recording all the detail that the HVX can deliver, then the 1080 mode would be kind of superfluous, so I'm assuming that's not the case. However, on the HDV cameras, they're about equivalent, the HD100's 720p mode retains about as much detail as the FX1's 1080i mode; the 1080i mode just uses 60% more pixels to store an equivalent-definition image. But then again, that's pretty much to be expected as the horizontal resolution is almost the same (1280 vs. 1440) and the vertical resolution advantage of the 1080i mode is squandered due to interlace de-flicker line blending, leaving a max. of about 800 usable lines of res, vs. 720p's 720, so they're about the same.

I suspect strongly that the HVX 1080 mode will actually be capturing and retaining more detail than its 720p mode though. They're both progressive, for one thing, so there's no interlace vs. progressive issue. And 1080 mode has 33% more horizontal and 50% more vertical pixels to work with. It would be my guess that 1080p mode would be preferable to 720p mode for just about every circumstance except a) variable frame rate shooting, and b) shooting for handing footage over to a 720p broadcaster. I do not expect 1080p mode to have twice as much definition as 720p mode though -- the lens and chips are going to limit how much definition can be recorded anyway. But I do expect that the 1080p mode will retain more definition than the 720p mode does.
 
Thank you Barry... How will you confirm if there is actually more resolution in 1080 - shooting them side by side on resolution charts, or based on future released specs by Panasonic?

john
 
what if the ccd are working with 960x720 and Pixelshift
in that case, why would anybody want to shoot with 1080p as it would have the same quality as 720p, but needs more space.
 
oli said:
what if the ccd are working with 960x720 and Pixelshift
in that case, why would anybody want to shoot with 1080p as it would have the same quality as 720p, but needs more space.
Click to expand...

Maybe because of compression loss. If you have got 960x720 native from the CCD, scale it up to 1280x1080 and compress that with DVCPRO HD and record it to P2, then on the PC convert it to a superiour codec (e.g. Cineform) or uncompressed and bring it back to 1280x720, you will suffer from less compression artifacts.

Of course the up+down scaling could add some blur to your image. So we will have to see. But if this method turns out to deliver a superiour 720p image I will take that path.

Jack
 
jdv said:
Thank you Barry... How will you confirm if there is actually more resolution in 1080 - shooting them side by side on resolution charts, or based on future released specs by Panasonic?
Click to expand...
Additional specs would be nigh unto meaningless, the only way to see if there's more definition is to observe it, through resolution charts, side-by-side pictures, or something like Imatest.
 
oli said:
what if the ccd are working with 960x720 and Pixelshift
in that case, why would anybody want to shoot with 1080p as it would have the same quality as 720p, but needs more space.
Click to expand...
This demonstrates a fundamental misunderstanding of what pixelshift does. It gives an actual, demonstratable, genuine 33% to 41% increase in observable resolution. It is NOT some cheapo scaling algorithm!

In any case, arguing about how it accomplishes it is nearly irrelevant as well. The end product is what will determine whether it's worth it to shoot in 1080p. If there's no observable resolution increase, then stick with 720 and get the space savings on the card. I'm guessing there will be a substantial resolution/observable definition increase, and that 1080p will prove to be well worth it.
 
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