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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 March 28th, 2011, 10:22 AM   #1
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Bad aliasing on JVC camera

Was doing a very basic drama shoot and using the HM100 as a master wide - something I've doen before for live shoots in 1080i50 HQ and I experienced severely aliased edges - almost to the point of making the video unusable.

I sort of got around it (or at least disguised it) with gaussian blur in AE - but this wasn't a detail problem as detail was set to -3.

You can see a small sample here uploaded to vimeo:


password: HM100

- in particular have a look at the curtains and note the vertical jaggies along the edges, the picture frame on the wall, etc. If anyone can shed any light on this would be greatly appreciated so I can avoid it in future. I'm wondering if it is an artifact of the stage lighting (which was a totally new venue for me)

The other two cameras, HM700s did not seem to experience the same problem.

thanks

John
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Old March 28th, 2011, 11:08 PM   #2
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Re: Bad aliasing on JVC camera

Password HM100 reported as "Invalid" for me.

Could your problem be related to this issue?
http://www.dvinfo.net/forum/jvc-gy-h...ve-mode-4.html
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Old March 29th, 2011, 01:22 AM   #3
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Re: Bad aliasing on JVC camera

You are seeing a classic example of 4:2:0 color sampling and interlaced frames. Red shows it the most.
Plus the HM100 has to do Pixel shifting as it is not a truly a1080 camera.

If you shoot a progressing frame like 1080 25p or 720 50p it will be a little better.
I always shoot in 720 mode now. I find the 720 looks better, less noise, and I can turn down the sharpinging to -6 or -9 and still have a nice picture.

If you turn down the sharpining down that far on 1080 mode it gets really soft.



If you view this on a good TV, it should look better as the TV help
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Old March 30th, 2011, 12:26 PM   #4
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Re: Bad aliasing on JVC camera

password: HM100

INVALID PASSWORD !!!!!!!!
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Old March 30th, 2011, 01:21 PM   #5
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Re: Bad aliasing on JVC camera

It works with lower-case: hm100
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Old March 30th, 2011, 11:36 PM   #6
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Re: Bad aliasing on JVC camera

sorry guys and gals - password is indeed lower case hm100

Andy - appreciate the feedback but I've used this camera as a second cam quite a lot but I hadn't seen that particular issue to anywhere near the same extent before.

I suppose it is a much higher cotnrast situation to say a dance concert or a close up on a corporate shoot but it still seems incredibly bad to me.

The 700s do pixel shifting as well from a 720 block and they were fine.

I'd shoot 720P50 if i could work out a decent workflow from there to 576i for DVD - however all my encoders seem to throw away every second frame rather than encode each frame to a field for smoooth motion.
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Old March 30th, 2011, 11:39 PM   #7
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Re: Bad aliasing on JVC camera

Quote:
Originally Posted by Jordan Hooper View Post
Password HM100 reported as "Invalid" for me.

Could your problem be related to this issue?
http://www.dvinfo.net/forum/jvc-gy-h...ve-mode-4.html
Jordan - I wondered that too as, even though I shot in interlaced, the vertical resolution (1080i) almost looks like it is only scanning every second line - the problems are much stronger on vertical lines than horizontal lines (eg the picture frame on the wall and the edges of the curtains)

password is hm100 (lower case) - sorry about that..
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