Z7 pixellization/grain isssue at DVinfo.net

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Sony HVR-Z7 / HVR-S270
Handheld and shoulder mount versions of this Sony 3-CMOS HDV camcorder.


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Old June 11th, 2009, 04:51 AM   #1
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Z7 pixellization/grain isssue

Hi,

I attached two test movies so you can check it out and tell me what's the problem.

The problem is when i maxed out the zoom, whenever an object passes through, a pixellization/grain problem occurs.

I shot with many different settings like "progressive/interlaced", different shutter and light conditions etc.

I'd like to ask that, is this a known problem of Z7 or a technical problem of mine like dirty head, bad sensor etc.

Thanks in advance,
/C
Attached Files
File Type: mov Test.mov (2.30 MB, 313 views)
File Type: mov test2.mov (919.4 KB, 248 views)
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Old June 11th, 2009, 07:46 AM   #2
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Hi Cuneyt - It looks like it might be a HDV compression problem to me, although it's a particularly nasty example of it if it is. The HDV format can struggle with fast changing scenes and the examples you post would seem to fit the criteria where HDV can breakdown.
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Old June 11th, 2009, 08:14 AM   #3
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Thanks for your reply Mike...

It's written that your camcorder is also Z7! Did you have any similar problems?
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Old June 11th, 2009, 10:07 PM   #4
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I guess my first impression is: What is it that you are trying to achieve by doing that? I don't get it.
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Old June 12th, 2009, 12:01 AM   #5
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I'm with you Greg, how about - stop waving your fingers in front of the lens... problem solved. Or am I missing something?

Actually, it may be a dirty head problem - GET YOUR DIRTY HEAD OUT OF THE SHOT!!!! LOL

Last edited by John Knight; June 12th, 2009 at 12:40 AM.
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Old June 12th, 2009, 03:17 AM   #6
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Cuneyt, I checked out the clips. What's wrong with them? They look pretty clear. Have you checked the footage out on a monitor or TV? You might find the image will be different than what you see on your computer.
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Old June 12th, 2009, 05:24 AM   #7
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With no intention of disrespect, I feel the obligation to tell my experience.

I worked with a wide range of cameras and in my job, every Sony ZX camera is seen as a pain. A pain because of the poor general quality of the Z1 (it's resolution on HD is near good SD upscaled), and because all of the ZX range have serious compression artifacts when the light intensity changes suddenly.

That makes this cameras a problem to us, and when it's about music concerts, almost unusable.

And this is a big problem, because of the big name Sony has, that made thousands of Sony ZX being buyed by lot of people. And therefore, we have to deal more often than we like with crappy Sony Zx fotage.

It's fustrating that even a cheap Canon HV20/30 at the same HDV codec and bitrate (25mbps) can deliver an almost compresion artifacts free footage in the same conditions.

But no matter what I say or even advice to friends, everyone keeps buying this cameras because of that Sony thing, that make people believe they are buying something else.

Sorry about my english.

Last edited by Javier Gallen; June 12th, 2009 at 09:48 AM.
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Old June 12th, 2009, 07:24 AM   #8
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looking at still frames I know what you mean with "pixellisation". Thats clearly a limit of HDV bandwith. too much information changes withing a short numbers of frames.

But:
So often people try to judge video footage by still frame examples.
Simply spoken: If its about video , watch the video, not a still.

Watching your mov files "in movement" I couldnt see the pixellisation in motion, so Id be happy with it.

Much more than your example, HDV limits are more easy to see in a motion video with a lot of changing details (leaves, grasses etc.) that would make it necessary to raise bitrates (see EX1 with 35 mbits or HDCAM with waaay higher bitrates).

@Javier
Well , I find either Z1 as well as the newer Z5/7 models (I own a Z7) absolutely worth the money. They are not full HD (1440x1080) , so they will never reach the same crispness or detail reproduction of any good full HD system.
Ive made great music and musical videos with Z1 AND Z7 (Z7 : be aware of flashes due to CMOS!) , pic quality also depends on our skills about lighting the scenes (or argue with the light designers ;-) ).
However, if anyone finds a HV20 to be better HDV quality than Zx - go for it.
I found the Z1 to be a work horse with some limitations (I HATE the iris wheel!) and found the Z7 to be a good compromise between professional manual handling and inputs (I also own XDCAM HD), picture quality and media handling (dont want to go for flash media right now).

My 2c.

Regards

ULi
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Old June 12th, 2009, 07:42 AM   #9
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Sorry but I think I've explained myself wrong. I don't see HV20 as a alternative, but as a camera who gives better HDV encoding at the same bitrate, wich is funny.

I think there are a lot of cameras who do the same, at the same price without so many issues. Of course, they're not Sony.
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Old June 12th, 2009, 02:23 PM   #10
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Cuneyt - Yes, unfortunately HDV is always liable to produce this effect occasionally, particularly in scenes which feature a lot of change from frame to frame (the classic example is waves on the sea). Unfortunately it's one of the compromises you have to accept when shooting HDV.

Anthony - look at the 9th frame of the first clip

Greg and John - I beleive the clips Cuneyt posted were camera tests designed to illustrate a serious issue Cuneyt had noticed. I don't think your replies are very helpful.
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Old June 12th, 2009, 10:46 PM   #11
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Quote:
Originally Posted by Mike Paterson View Post
Greg and John - I beleive the clips Cuneyt posted were camera tests designed to illustrate a serious issue Cuneyt had noticed. I don't think your replies are very helpful.
Mike, I am sorry I offended the internet police but I would still like an answer to my question? What is he trying to achieve. Or is this like the situation where someone complains about CMOS chips and rolling shutter by doing violent whip pans that no client will want or buy. Or is he is really trying to achieve an effect. I would like to know what he is trying to achieve. Thank you very much. BTW, I suppose you think your blandly replying it is just something he will have to live with because of the HDV codec is so helpful. If he tells us what he is trying to accomplish maybe some of the folks on here might actually have a suggestion that really will be helpful.
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Old June 13th, 2009, 10:21 AM   #12
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Mike, you have a good eye. I can see that pixellation, it shows on frame #9. Cuneyt, thanks for bringing this to light. I'll be on the lookout for this with my own footage. Does it only happen when you're zoomed in? Good luck!
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Old June 13th, 2009, 09:09 PM   #13
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Reminds me of this clip... esp what he says at 01:30

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Old June 14th, 2009, 01:19 AM   #14
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Cuneyt,

Proviso, I am unable to look at your test video's.

Grain is an issue with the Z7 at zero gain. Sony sold it as a great low-light camera but what they didn't tell you was that the gain default (0db) is actually a gain applied setting.

A colleague of mine bought the camera one day and went on a shoot in S. India the next and came back with a short time lapse that he'd done near sunset. As the light diminishes the gain grain becomes more an more apparent... an ugly discovery for him.

Sony doesn't say what gain setting is true 0db but other posts here and my experience suggests -6db. If you haven't set the gain back on your Z7 grain will be noticeable to the keen eye even under well lit conditions when objects of greater contrast enter the view.
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Old June 14th, 2009, 12:59 PM   #15
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I'm not convinced that the Z7's 0 gain is actually gain applied. I've tested it extensively in the field and believe that too much detail is lost when going to -6db. I know that Doug Jensen from Vortex Media and others suggest that you can set gain to negative, but I recommend users check it out for themselves before making -6db the default.

As for the gain-grain in the India footage, I dont think an assessment of black / grain can be done accurately with time-lapse footage. From what I understand the image quality diminishes with Z7 time-lapse.
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