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Panasonic LUMIX G / GF / GH / GX Series
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Old March 24th, 2011, 12:13 PM   #1
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New 21 Page Review of the GH-2

DpReview.com : Panasonic GH-2 Review
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Old March 25th, 2011, 07:39 PM   #2
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Re: New 21 Page Review of the GH-2

At least one spec is inaccurate on the first page. You can not output 1080 60p in 60i.
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Old March 25th, 2011, 08:57 PM   #3
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Re: New 21 Page Review of the GH-2

William, are you referring to "1920 x 1080p 24fps* (approx 23 or 17 Mbps)"? That is accurate, isn't it? Or are you referring to something I missed?
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Old March 25th, 2011, 09:12 PM   #4
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Re: New 21 Page Review of the GH-2

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Originally Posted by William Hohauser View Post
At least one spec is inaccurate on the first page. You can not output 1080 60p in 60i.
From Panasonic's own GH2 specs "[Full HD] 19201080, 60i (sensor output is 60p)". Technology can be puzzling.
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Old March 25th, 2011, 09:18 PM   #5
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Re: New 21 Page Review of the GH-2

I don't use it, at least yet. I just can't see it for live event work. In addition, what do you do with the footage for DVD? I have a lot to learn about these frame rates.
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Old March 26th, 2011, 01:37 PM   #6
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Common DSLR Video Resolutions--reference

Common DSLR video resolutions Progressive and Interlaced
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Old March 26th, 2011, 06:33 PM   #7
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Re: New 21 Page Review of the GH-2

Let's get a couple of Panasonic specs clarified first.

They claim in most places that the camera can record video at 1080 60i/50i or 1080 24p. You can encode a progressive image into an interlaced video stream but it requires a few caveats. First the encoding hardware must be fast enough to deal with the computational issues and has enough memory buffer to hold the frames while the computation is taking place. The few instances I have seen a progressive image embedded into a progressive stream the progressive frame rate is significantly slower than the interlace frame rate. 30p into 60i for example or more commonly 24p into 60i. This is what the GH2 puts out over the HDMI circuit. The AVCHD video files are flagged as 24p when imported into an editing program. To encode 60p into 60i requires a bit of hardware design that I suspect the camera doesn't have. A shutter speed of 120th/sec would be helpful to accomplish the task and I don't see the camera making that adjustment or asking for it. A typical 60i camera shoots half resolution frames at least 100th/sec in normal shooting. Interlacing is the oldest television compression method dating back to the 1930's. It works as it halves the bandwidth needed for image transmission which is why it's still with us now.

720 60p is a different matter as the frame sizes are smaller than 1080p therefore less of a chore for the hardware or transmission.

I did a brief test of the camera to see how the sensor was picking up the image at different frame rates. The camera was set in full manual, 3200iso, 1.4f-stop and shutter at 1/50th. The first image, 0091, is 1080i. The second image, 0092, is 24p. I panned quickly in both instances almost at the same place (forgive the ugly, ugly shot). The stills were extracted with QuickTime player. As you can see, 0091, has a double image which seems to indicate interlace image capturing which means that half of the image is captured slightly later then the first but both are combined to make a single full resolution frame. The second still is just motion blurred which indicates a progressive capture of the image. The interlaced image is also darker which might mean that the camera is automatically changing the shutter.

1080 60p video capture is a tough job to ask of a camera which is why the HDV consumer format never considered it. If there is a way to record true progressive 30f in the 1080i mode, I would be grateful to find out.
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