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JVC GY-HM 70/100/150 Series Camera Systems
GY-HM70, HM100, HM150 recording AVCHD MP4 & QuickTime .MOV to SDHC cards.


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Old August 19th, 2009, 05:19 PM   #1
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HM100 Record Mode

Okay, here's something that my poor brain is struggling to understand. Record modes on my HM100 (PAL in 1080) include 1920/50i, 1920/25p, 1440/50i in both HQ and SP. It suddenly struck me - the sensors are native 16X9 - so why/how is there a 1440X1080 option? This is effectively 4:3 ---- so how is this being achieved?

When I shoot SD on a 2/3 inch chip camera for UK telly, I shoot 16:9 widescreen. This means using the anamorphic function ability of the camera to squeeze a 16:9 picture onto its 4:3 sensors. Fine. For broadcast the image is unsquished and hey presto -- 16:9.

What on Earth is going on with the 1440X1080 image on the HM100? Is it effectively squishing a 16:9 image down to 4:3 ? If so, why does the viewfinder show a 16:9 image? Am I barking up the wrong tree? Is it time for another glass of wine?

Ack.

Cotty
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Old August 19th, 2009, 05:43 PM   #2
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It is the way HD was recorded for HDV cameras and it is the same as anamorphic or squeeze.
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Old August 19th, 2009, 05:53 PM   #3
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Quote:
Originally Posted by Steve Cottrell View Post
Okay, here's something that my poor brain is struggling to understand. Record modes on my HM100 (PAL in 1080) include 1920/50i, 1920/25p, 1440/50i in both HQ and SP. It suddenly struck me - the sensors are native 16X9 - so why/how is there a 1440X1080 option? This is effectively 4:3 ---- so how is this being achieved?
Cotty
The pixels aren't square, they are rectangular (longer wide than tall). The square pixel size of the frame is 1920x1080.
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Old August 20th, 2009, 11:55 AM   #4
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Oh brother. Anyone got a decent primer online anywhere - I need a bit more reading...

Cotty
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Old August 20th, 2009, 01:29 PM   #5
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Here is some information:
Final Cut Pro 7 Professional Formats and Workflows
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Old August 21st, 2009, 05:14 AM   #6
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Thanks for the link.

I still was curious as to why HDV is recorded ay 1440X1080 and the link below helped me...

Why is BBC HD 1440? - Technical - Digital Spy Forums

Cotty
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Old August 27th, 2009, 12:40 PM   #7
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You find that confusing.. how about these.. :)

If you think that is weird, how about DirecTV and Dish network broadcasting HD content!

Dish's 1080i last I checked was 1440x1080i and DirecTV was closer to 1080x1080i. Meanwhile 720p broadcast channels were still 1280x720p. funny eh? Both broadcasters have been dropping their resolution due to bandwidth artifact problems.

But lets not stop there at that the confusion. I love all these 1080p cameras under $40,000. I don't think many of them is 1080p, and few of them are not even 720p. Most are 960x540p and uprezzed (DVCPRO-HD cameras for instance) and others are 1440 x 1080i/p depending upon price range, (newer sony's for example.. some claim to be native progressive with weird 45' chip rotation... .. )

so to say the least there is lots of stretching and pulling, both of the video signal and the truth. Though they have gotten a lot better at the pixel shift and uprezzing. I think it's why 720p with a decent codec and a good lens still holds it own from a JVC vs a camera costing $30-40k. When you are in that range, the person on the other end of the eyepiece tends to make the bigger difference.
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