Z7 pixellization/grain isssue at DVinfo.net

Cuneyt Durukan · June 11th, 2009, 03:51 AM

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

Mike Paterson · June 11th, 2009, 06:46 AM

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.

Cuneyt Durukan · June 11th, 2009, 07:14 AM

Thanks for your reply Mike...

It's written that your camcorder is also Z7! Did you have any similar problems?

Greg Laves · June 11th, 2009, 09:07 PM

I guess my first impression is: What is it that you are trying to achieve by doing that? I don't get it.

John Knight · June 11th, 2009, 11:01 PM

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

Anthony Trotter · June 12th, 2009, 02:17 AM

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.

Javier Gallen · June 12th, 2009, 04:24 AM

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.

Uli Mors · June 12th, 2009, 06:24 AM

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 I´d 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.
I´ve 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

Javier Gallen · June 12th, 2009, 06:42 AM

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.

Mike Paterson · June 12th, 2009, 01:23 PM

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.

Greg Laves · June 12th, 2009, 09:46 PM

Quote:

Originally Posted by Mike Paterson

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.

Anthony Trotter · June 13th, 2009, 09:21 AM

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!

John Knight · June 13th, 2009, 08:09 PM

Reminds me of this clip... esp what he says at 01:30

YouTube - Everything is amazing, nobody is happy...

T.G. Lawrence · June 14th, 2009, 12:19 AM

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.

Anthony Trotter · June 14th, 2009, 11:59 AM

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 don’t 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.

June 11th, 2009, 06:46 AM	#2
Mike Paterson Regular Crew Join Date: Jul 2005 Location: London, UK Posts: 99	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. __________________ www.pfilm.co.uk

June 11th, 2009, 11:01 PM	#5
John Knight Major Player Join Date: May 2008 Location: Auckland, New Zealand Posts: 588	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 11th, 2009 at 11:40 PM.

June 12th, 2009, 04:24 AM	#7
Javier Gallen Regular Crew Join Date: Jul 2005 Location: Spain Posts: 67	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 08:48 AM.

June 12th, 2009, 01:23 PM	#10
Mike Paterson Regular Crew Join Date: Jul 2005 Location: London, UK Posts: 99	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. __________________ www.pfilm.co.uk

June 11th, 2009, 07:14 AM	#3
Cuneyt Durukan Tourist Join Date: Aug 2008 Location: Istanbul, Turkey Posts: 3	Thanks for your reply Mike... It's written that your camcorder is also Z7! Did you have any similar problems?

June 11th, 2009, 09:07 PM	#4
Greg Laves Major Player Join Date: Nov 2007 Location: Corpus Christi, TX Posts: 640	I guess my first impression is: What is it that you are trying to achieve by doing that? I don't get it.

June 12th, 2009, 02:17 AM	#6
Anthony Trotter Regular Crew Join Date: Jan 2009 Location: Tokyo, Japan Posts: 51	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.

June 12th, 2009, 06:24 AM	#8
Uli Mors Major Player Join Date: May 2006 Location: Germany Posts: 565	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 I´d 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. I´ve 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

June 12th, 2009, 06:42 AM	#9
Javier Gallen Regular Crew Join Date: Jul 2005 Location: Spain Posts: 67	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.

June 13th, 2009, 09:21 AM	#12
Anthony Trotter Regular Crew Join Date: Jan 2009 Location: Tokyo, Japan Posts: 51	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!

June 13th, 2009, 08:09 PM	#13
John Knight Major Player Join Date: May 2008 Location: Auckland, New Zealand Posts: 588	Reminds me of this clip... esp what he says at 01:30 YouTube - Everything is amazing, nobody is happy...

June 14th, 2009, 12:19 AM	#14
T.G. Lawrence Regular Crew Join Date: Oct 2008 Location: Vancouver, Canada Posts: 27	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.

June 14th, 2009, 11:59 AM	#15
Anthony Trotter Regular Crew Join Date: Jan 2009 Location: Tokyo, Japan Posts: 51	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 don’t 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.