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Old December 31st, 2013, 12:01 PM   #1
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x920 Artifacting - What on Earth is This?

Could anyone with more experienced eyes help diagnose what I'm looking at?

Attached are two 100% crops from from a test shoot with some crows. In the 2nd frame, when the bird's body is moving, the dark areas of motion pixellate heavily. I'm guessing these are compression artifacts?

I'm baffled, since comparable files coming out of an earlier consumer-grade Panasonic (SDT750) never contain anything like this; shadowed motion from that camera is a gradient blur, not blocky. (I'm not trying to nitpick: when slowed to half-speed, the birds pixellated motions remind me of that old Predator movie...not exactly what I'm going for here.)

I'd hoped the x920 would be an inexpensive 'upgrade', but given my primary subject (fidgety black birds in a high-contrast environment), I'm having second thoughts.

Would that old standby of "you need a higher bitrate" help here? Any recommendations for more suitable gear would be appreciated. I'd considered a GH3, but I really need a deeper working dof.

(Shot at 1080/60p. Manual focus, +1 'Exposure Adjust.' Everything else auto. Settings when checked: 1/60, f3.4)

http://www.dvinfo.net/forum/attachme...1&d=1388510243
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x920 Artifacting - What on Earth is This?-x920_artifacting-2.jpg  
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Old December 31st, 2013, 01:44 PM   #2
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Re: x920 Artifacting - What on Earth is This?

Yes, the bitrate argument works for these artifacts.

The fact is, AVCHD 2.0 at 28mbps is not enough to properly capture 1080p60. High motion will suffer these problems, it's unavoidable with the AVCHD 2.0 codec. The GH3 uses 50mbps which remedies this exact issue.

Unfortunately, the next step up that actually has a decent codec is the Sony 4K PXW-Z100, which can record 1080p60 with a really high bitrate.
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Old December 31st, 2013, 02:52 PM   #3
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Re: x920 Artifacting - What on Earth is This?

<Sigh.> Thanks.

At least the birds didn't poop on the camera. Back it goes.

(Downloading DaVinci Resolve for a test drive; no 60p, but the BMPCC (and GH3) are the only high-bitrate options that fit my budget.)
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Old December 31st, 2013, 03:04 PM   #4
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Re: x920 Artifacting - What on Earth is This?

A GH3 with a 14mm wide-angle would do well for a unattended camera for the birds.
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Old January 1st, 2014, 04:25 AM   #5
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Re: x920 Artifacting - What on Earth is This?

Hi Kris

Even my Panny HMC82's were terrible when shooting at 50P (we are PAL here) and even on slow movement (like a bride walking towards you) I used to often get pixellation on their cheek bones ??

My solution was to end up shooting at 50i and then just de-interlacing in my NLE and even with my new Sony cams I still shoot in 50i and always get a consistent result. As Jack says you need a high bitrate to cover motion with progressive footage ... 50 mbps will cut it but 28mbps usually will give you hassles..in fact the subject doesn't even have to move!! Handheld camera movement is often enough to cause pixellation! This is probably the reason that when panny brought out the AC-130 ..50/60P was not an option!

Chris
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Old January 1st, 2014, 07:23 PM   #6
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Re: x920 Artifacting - What on Earth is This?

Out of curiosity, I checked files from my old camera for compression artifacts.

They're there, of course, but they're much more 'organic', a kind of posterized banding. Much easier on the eye than the linear tearing and blockiness of the newer model, at least under these conditions. (see attachment)

---

Chris: Good point about hand holding taxing the codec: most of the frame in my stuff is static, so I've probably been lucky. And the moving shadow detail is usually crushed to black.

Jack: Any idea if the 14mm is better than the 14-42 when stopped down? I don't need the speed, and at the moment it's half the price. (I briefly owned a G6 and the 14-42 kit zoom, which seemed great, but never compared it with a prime.)

Thanks again.

http://www.dvinfo.net/forum/attachme...1&d=1388621651
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x920 Artifacting - What on Earth is This?-vs-750.jpg  
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Old January 2nd, 2014, 01:47 AM   #7
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Re: x920 Artifacting - What on Earth is This?

The 14-42 is going to be less fast compared to the 14mm fixed. The 14mm F1.7 will be much better stopped down compared to the F3.5 already being lost with the 14-42.
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Old January 3rd, 2014, 05:30 PM   #8
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Re: x920 Artifacting - What on Earth is This?

I have a TM700 and don't get that kind of macro blocking at all. Just a smooth blur on fast moving objects in 1080-60p.

Curious what your exact settings were on the x920 when it did that? Do you remember how much gain was being used at the time?

I was looking at picking up a newer X920 and am interested in seeing how it compares.

Cheers,
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Old January 7th, 2014, 12:45 PM   #9
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Re: x920 Artifacting - What on Earth is This?

Quote:
Originally Posted by Pete Carney View Post
I have a TM700 and don't get that kind of macro blocking at all. Just a smooth blur on fast moving objects in 1080-60p.
That's just it...I've reviewed countless hours of footage on my older camera (which I understand is essentially the TM700 bundled with a goofy 3D attachement) and never saw this sort of thing...regardless of settings. The artifacting, even at its most severe, is always more organic looking. (I've attached the screen shots comparing simliar shots from the 2 cameras.)

Quote:
Originally Posted by Pete Carney View Post
Curious what your exact settings were on the x920 when it did that? Do you remember how much gain was being used at the time?
Auto later checked at f3.4 (0db), 1/60.

Quote:
Originally Posted by Pete Carney View Post
I was looking at picking up a newer X920 and am interested in seeing how it compares.
Panasonic just announced 2014's lineup of consumer-oriented camcorders. Looks like they've abandoned the 3-chip 3MOS system in consumer cameras, which means the x920's new sensor tech might have been a one-off.

http://www.dvinfo.net/forum/attachme...1&d=1389117469
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x920 Artifacting - What on Earth is This?-vs-750.jpg  
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