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Old March 31st, 2009, 02:31 PM   #1
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Quality of encoding at various resolution and frame rate

The camcorder records 1080i60, 1080p30, 1080p24, 720p60, 720p30 and 720p24, all at 21Mbps each. So, in theory, 720p24 should have the least compression and produce a much cleaner image at 21Mbps then 1080p30 at 21Mbps, since 24p is native. Same could hold true, but less apparent, with 1080p24 being better then 1080p30. Or am I missing something? I'm asking, because contrary to the P2 recording time chart, there are no recording time differences due to frame rates, only in compression levels.

Also, I've used the HVX170 for a green screen shoot, and noticed that it is a bit softer on the edges in 1080p compared to 720p. Normal because of the pixel shifting from a 960x540 bloc. Will I notice the exact same effect on the HMC150?
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Old April 3rd, 2009, 01:57 PM   #2
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The 150 does indeed perform as you expect, 720p compresses cleaner than 1080p, which is cleaner than 1080i.

Frame rate differences do come into play as well; 720/24p records cleaner than 720/60p -- but not as huge a difference as you might expect. The additional frames only take up a very little bit of additional compression bandwidth since there's less difference between frames at 60p than there is at 24p.

1080/60i is the least-effective to compress. Interlace is always harder on compression algorithms than progressive.

You will get a little bit sharper picture in 1080p vs. 720p, but perhaps the bigger difference is in the chroma resolution. 1080p mode records noticeably more color resolution than 720p mode; even though the overall luminance resolution is pretty comparable between them, 1080p mode carries 2.25x as much chroma information as 720p mode does. So for greenscreening, etc., I'd definitely suggest 1080p over 720p, and 720p over 1080i.
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Old April 3rd, 2009, 07:19 PM   #3
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If 1080p records 2.25 times more chroma information, and 720p is 2.25 time smaller then 1080p, isn't it mathematically the same, all proportions considered? Or maybe the advantage would be in capturing 1080p, and downresing in post using a 4:2:2 codec to maximize chroma information for a 720p final image?
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Old April 6th, 2009, 10:56 AM   #4
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So, for the shooter who will ultimately deliver the footage on NTSC widescreen, is there a best mode to shoot in?

I started out shooting 1080i on the HMC-150 to match my other 1080i cameras. Then I switched to 720P30.

Maybe I should go to 1080P30 for a little better color & sharpness?


FWIW, I think we are splitting hairs on this topic, and they are all very similar, high quality modes. But I would like I optimize the HMC for the best possible productions.
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Old April 6th, 2009, 11:31 AM   #5
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Quote:
Originally Posted by Barry Green View Post
The 150 does indeed perform as you expect, 720p compresses cleaner than 1080p, which is cleaner than 1080i.

Frame rate differences do come into play as well; 720/24p records cleaner than 720/60p -- but not as huge a difference as you might expect. The additional frames only take up a very little bit of additional compression bandwidth since there's less difference between frames at 60p than there is at 24p.

1080/60i is the least-effective to compress. Interlace is always harder on compression algorithms than progressive.

You will get a little bit sharper picture in 1080p vs. 720p, but perhaps the bigger difference is in the chroma resolution. 1080p mode records noticeably more color resolution than 720p mode; even though the overall luminance resolution is pretty comparable between them, 1080p mode carries 2.25x as much chroma information as 720p mode does. So for greenscreening, etc., I'd definitely suggest 1080p over 720p, and 720p over 1080i.
What if you are not shooting for greenscreen? Is 720p better than 1080p because it is compressed less or does having more chroma in 1800p make it the better option?

Thanks,

Daniel Weber
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Old April 6th, 2009, 04:39 PM   #6
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Um... good question... :)
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Old April 6th, 2009, 08:43 PM   #7
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Well, if you're watching on a large screen HDTV, I'd go with 1080p, as there is a tad more resolution. It's perceptible enough. I agree that it's not night and day, but after grabbing stills from both, and comparing them in Photoshop, there is definitely more detail. As for the better compression... I've shoot the same scene at both resolution, and from what I was able to perceive and analyze, I can't really say for sure if 720p is that much better compression wise. But detail wise, 1080 is better... not a whole lot, but enough.

So in essence, practically, you'll better notice the increased resolution of 1080p then the more efficient compression of 720p.
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Old April 7th, 2009, 12:44 PM   #8
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Originally Posted by Frederic Segard View Post
Well, if you're watching on a large screen HDTV, I'd go with 1080p, as there is a tad more resolution. It's perceptible enough. I agree that it's not night and day, but after grabbing stills from both, and comparing them in Photoshop, there is definitely more detail. As for the better compression... I've shoot the same scene at both resolution, and from what I was able to perceive and analyze, I can't really say for sure if 720p is that much better compression wise. But detail wise, 1080 is better... not a whole lot, but enough.

So in essence, practically, you'll better notice the increased resolution of 1080p then the more efficient compression of 720p.
Fred:

In part of my testing, I hooked the HMC-150 up to a fresh 40" 1080P calibrated LCD monitor via the HDMI. That takes the compression aspect out of the image.

I then switched through the modes and scrutinized the scenes. The HMC-150 only seems to output either 1080i or 720P(30?) off the HDMI. On the 40" monitor, looking very closely at multiple different scenes framed and using 1080i and 720P, there was no difference at all visible. In fact, if the monitor didn't report the type of signal it was recieving, I would have thought the HDMI display mode did not change.

I don't know exactly what this means for SDHC captured material. I think the HDMI is 4:2:2 color space output, so I would guess color would look the same for 1080i or 720P, where when captured to the SDHC, if would not be.

Okay this is a little bit of pixel peeping fanatacism, but here are some other things you will see a few inches from a 40" screen when on the HDMI and tweaking the camera. 1. I don't think the lens and sensor are fully matched (MTF) in resolving ability. There are some objects (outside of the obviously focused regions) the camera simply cant create a focused image of. Example, features in front and features behind of a tree in the extreme distance will be in focus, yet the leaves on the tree in the middle are fully unable to come into focus or resolve, regardless of any camera settings (F stop). 2. On manual focus, the focus will creep ever so slightly, every time, immediately after releasing the focus ring, perceptibly altering the focus. It's an electronic issue, not mechanical as the ring dosent move any further after release.

With that said, you will never see any of this on the camera display or in a render to NTSC widescreen. If Panasonic increases the resolution of these 1/3" cameras in the future, it will be a totally unbeatable camera. However, a new lens and sensor is a lot to ask for, that's basically a new camera.
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