Wobbly snow at DVinfo.net
DV Info Net

Go Back   DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony XDCAM EX Pro Handhelds

Sony XDCAM EX Pro Handhelds
Sony PXW-Z280, Z190, X180 etc. (going back to EX3 & EX1) recording to SxS flash memory.

Reply
 
Thread Tools Search this Thread
Old December 12th, 2007, 03:34 AM   #1
Major Player
 
Join Date: Mar 2005
Location: canterbury
Posts: 411
Wobbly snow

I created a new thread here rather than add it to Colins because this is something specific, but if you look at the snow 60fps shot from

http://blog.lib.umn.edu/mcfa0086/dis...ne/102124.html

(it's the 3rd one down)

Colin says it exhibits the rolling shutter which maybe it does, but im not sure. There's a weird effect like the jello effect but i wouldn't have thought the camera was moving enough to create a rolling shutter artifact. You can see the various parts of the frame wobbling about quite obviously (unusable in fact). Im looking at the 720p download as i cannot open the original files.

I don't understand how the snow would create this as it's not moving fast enough and also the worst you'd get with a vertical rolling shutter is a snow flake disappearing!

This seems to be something else. OIS? A compression artifact? A combination.

I assume it's on the original because Colin observed it and said it was rolling shutter.

Does it do this in rain? Or other areas with changes over the screen? I hope not because that would be a real world problem. Is it only at 60fps?

Can anyone shed some more light on this?

cheers
paul
Paul Curtis is offline   Reply With Quote
Old December 12th, 2007, 04:06 AM   #2
Major Player
 
Join Date: Mar 2007
Location: Norfolk, UK
Posts: 627
I'd be surprised if it's caused by the snow as the wobble is happening on the rails too. It looks like it was shot through rising warm air. Was it shot through a window?

Paul.
__________________
Blog: www.pauljoy.com
Company: www.videotrader.co.uk
Paul Joy is offline   Reply With Quote
Old December 12th, 2007, 04:24 AM   #3
Major Player
 
Join Date: Mar 2005
Location: canterbury
Posts: 411
Looking at the 24fps version of the snow underneath it does exhibit it but to a lesser degree. I don't think it's a window (although it looks cold enough that if it was me i would be inside for sure...)

I wonder if it's the OIS compensating madly and *that* causing a rolling shutter wobble? Perhaps 60fps is making the OIS work harder.

(Im assuming OIS was on... Colin?)

cheers
paul
Paul Curtis is offline   Reply With Quote
Old December 12th, 2007, 06:25 AM   #4
Trustee
 
Join Date: Sep 2005
Location: Gilbert, AZ
Posts: 1,896
Yes, that was strange, but under those camera conditions, it does not appear to be rolling shutter related.
Steven Thomas is offline   Reply With Quote
Old December 12th, 2007, 12:22 PM   #5
Sponsor: divergent media
 
Join Date: Jun 2004
Location: St. Paul, MN
Posts: 201
I was outside when I shot it. That's on a pretty tight zoom as well. OIS was on, but OIS really shouldn't be able to cause that sort of effect.

If you go frame by frame, you can see the jello effect very clearly. I still think it's a consequence of rolling shutter + the overcrank framerate, which accentuates changes between frames.

The only other thing it could be in my mind is an issue with the codec - motion vectors getting screwed up. It's possible, but I would think I would see evidence of that in other places as well.

I'm just as curious as everyone else though!
__________________
Divergent Media Support
www.divergentmedia.com
Colin McFadden is offline   Reply With Quote
Old December 12th, 2007, 12:32 PM   #6
Sponsor: divergent media
 
Join Date: Jun 2004
Location: St. Paul, MN
Posts: 201
To try and diagnose a bit further, I just did a little screen capture of me scrubbing back and forth over a few frames in the original. Might help?

Original file (Apple Intermediate Codec): https://mediamill.cla.umn.edu/mediam....php?orig=4572

H264 640x480 version:
https://mediamill.cla.umn.edu/mediamill/embedqt/6881
__________________
Divergent Media Support
www.divergentmedia.com
Colin McFadden is offline   Reply With Quote
Old December 12th, 2007, 12:35 PM   #7
Major Player
 
Join Date: Mar 2005
Location: canterbury
Posts: 411
My thinking about the OIS was

- the OIS is a mechanical solution that moves the lens elements around
- the snow is confusing the electronics driving the elements

so i'm guessing that internally the lens elements might be shifting around imperceptably to stablise something that doesn't need stablising, they're doing this so fast that the rolling shutter is being shown up.

But screwed up motion vectors could also explain it, however you'd have thought that the compression algorthim would handle that. In fact we know mpeg2 can handle that otherwise we'd get no DVDs with snow scenes!

You can see the effect, less pronouced in the 24fps version too.

It's odd. Is it still snowing there? Maybe having a go without OIS would solve this?

I don't see how the rolling shutter would be shown up with simple movement like that. the whole view has to change a lot from line to line to show up during the read out phase and the background is not moving that much. We'd see the jello effect all the time if hand holding on a long lens would be enough.

cheers
paul
Paul Curtis is offline   Reply With Quote
Old December 12th, 2007, 12:37 PM   #8
Sponsor: divergent media
 
Join Date: Jun 2004
Location: St. Paul, MN
Posts: 201
We may have some snow tomorrow morning. I also passed the video along to a technical contact at Sony to see what they make of it.
__________________
Divergent Media Support
www.divergentmedia.com
Colin McFadden is offline   Reply With Quote
Old December 12th, 2007, 12:43 PM   #9
Sponsor: divergent media
 
Join Date: Jun 2004
Location: St. Paul, MN
Posts: 201
The reason I don't think that it's OIS is that OIS should be independent of what's actually being recorded - they do it based on accelerometers/gyroscopic sensors in the body, don't they? I'd certainly believe it if the camera had electronic stabilization (see my post here http://blog.lib.umn.edu/mcfa0086/dis...ne/098974.html) but... hrm..
__________________
Divergent Media Support
www.divergentmedia.com
Colin McFadden is offline   Reply With Quote
Old December 12th, 2007, 05:01 PM   #10
Trustee
 
Join Date: Sep 2005
Location: Gilbert, AZ
Posts: 1,896
I Agree.
Well, just in case, try it again with OIS OFF, then ON.
Steven Thomas is offline   Reply With Quote
Old December 12th, 2007, 07:10 PM   #11
Regular Crew
 
Join Date: Feb 2006
Location: Vancouver, WA
Posts: 86
Colin, were you in auto focus or manual focus on this shot?
Forrest Burger is offline   Reply With Quote
Old December 12th, 2007, 07:11 PM   #12
Sponsor: divergent media
 
Join Date: Jun 2004
Location: St. Paul, MN
Posts: 201
I believe it was autofocus
__________________
Divergent Media Support
www.divergentmedia.com
Colin McFadden is offline   Reply With Quote
Old December 12th, 2007, 07:14 PM   #13
Regular Crew
 
Join Date: Feb 2006
Location: Vancouver, WA
Posts: 86
I wonder if that might be coming in to play...the camera trying to focus on the snow flakes at different focal lengths, combined with the OIS?
Forrest Burger is offline   Reply With Quote
Old December 12th, 2007, 09:52 PM   #14
Major Player
 
Join Date: Dec 2006
Location: Va Beach, Va
Posts: 241
Quote:
Originally Posted by Colin McFadden View Post
I believe it was autofocus
I'm thinking that's the issue right there.
Brad Vaughan is offline   Reply With Quote
Old December 12th, 2007, 10:09 PM   #15
Trustee
 
Join Date: Dec 2003
Location: Houma, La.
Posts: 1,400
Images: 5
First impression was that it might be the rolling shutter "jello" look, but it just didn't make sense. It seemed to be isolated to certain areas and rolling shutter should be apparent over the entire frame.
My next guess was OIS strangeness but I dunno.. that just didn't seem right either.
I've just about convinced myself that it's a thermal of some sort.
But then again someone mentioned AutoFocus.

Go full manual and see if you can get this to repeat.
__________________

-Ethan Cooper
Ethan Cooper is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

B&H Photo Video
(866) 521-7381
New York, NY USA

Scan Computers Int. Ltd.
+44 0871-472-4747
Bolton, Lancashire UK


DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony XDCAM EX Pro Handhelds

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



All times are GMT -6. The time now is 08:37 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2024 The Digital Video Information Network