GL2 / XM2 Frame mode
 

Jerkiness or Strobing in GL2 Frame mode

Several people with PAL GL2s have reported jerky images when panning in Frame mode, at their 25fps rate. What has been the experience regarding this from those who are shooting in Frame mode with NTSC GL2s with 30fps? Is this glitch diminished by the higher frame-rate? I wonder if true progressive-scanning cameras, like the AG-DVX100, have such a pronounced problem with jerkiness when panning?

This is a "feature" of any progressive scan (or in the case of Canon it's pseudo-progressive scan) video camcorder. Camera movements must be done sloooowly, cinematic style. On the Panasonic DVX100 it's even more pronounced due to the slower frame rate.

Steve

Regarding the NTSC gl2, I use the frame mode exclusively and I almost never see a problem. 90% of the time its when I'm just not paying attention to how I'm shooting, or if I'm trying to hand hold without a proper support--essentially bad camera work to start with.

Here's a clip that has a lot of movement (shot on a gl1--which I think uses a slightly less smooth version of the frame mode), I don't think there is much of a problem anywhere.

http://homepage.mac.com/barrygoyette/iMovieTheater4.html

And some tips(which you may have already read)

http://www.dvinfo.net/conf/showthread.php?s=&postid=20690

Barry

I'm pretty sure that the XM2 is worse at this then the GL2. I panned really slooooow last night in frame mode and I still got the jitter really badly. It's just not usable at all I'm not just being fussy. The one thing I didn't try was to to put the shutter at 1/25 because in normal mode this makes it jerky so I didn't even think of trying it in anything less then 1/50 but I will give 1/25 a go as well but I have a feeling it will make it worse not better.


Peter B

Peter..

try this...Its just a hunch (I haven't tried it yet):

Do a custom preset with the sharpness turned all the way down, and a setup of +1 or +2, this might lessen the problem. I noticed yesterday while panning a picket fence (yikes) that if I took the image a little out of focus, it didn't strobe, not even a little. Maybe softening the edge will do the same thing...its worth a shot. If it works, then you could experiment with increasing the sharpness till it hits the sweet spot.

Barry

Sounds like an idea, I'm leaving work now so I'll post tomorrow to tell my results. Seriously though the effect at the moment is similar to the strobe effect in effects mode...ok not that bad but pretty close.

One other tip is if you are shooting from a tripod, make sure the image stabilizer is off.

Ok I had a go last night and did get a better result. I turned the sharpness down and the setup a little bit up. It gave a lot smoother result but I don't think you could use it to do chase scenes like Barry did in his. If you zoom in and out it's perfect you can't detect it at all but panning slowley still gives a slight jitter, but it is more of a jitter then a jolt or the strobe effect. Im going to try it in better light as well because so far it's always been in indoor lighting. I work late so don't get back before 8:00 but I'll try over the weekend.


Peter B

my favorite frame mode setting is with shutter at 1/25th
If you move the camera fast enough that it looks strobey, the image blurs because the shutter is open for so long. This blur greatly reduces the amount of strobe perceived by the viewer, and looks cool & filmy!

I tried it on my skateboard yesterday, the result looked great.

I also tried it with shutter on 1/800, and the image was so sharp & fast moving it made my friend feel ill!

The only problem is if you're shooting stuff of varied speed for example a documentry or short film I feel that it would just hinder your creativity always having to worry about what shot you can have and at what speed just for that filmic look. I'd rather work on the lighting to get the film look and let my creativity run free not becoming frustrated when a shot I know would look really cool can't be used because it would jitter.


Peter B

For what it's worth, Peter, I tried turning down the sharpness on my gl2, and I'm pretty amazed at how much any hint of stuttering has gone away. I shot some more footage yesterday of Kaori running through the forest, all hand held, with some pretty questionable camera work, and everything looked just fine. I know this doesn't help xm2 owners, but I thought this might be of interest to those using the ntsc version. I'm hoping that your normal daylight tests will give you better results, as I can't see why the xm2 (even with the lower framerate) would be vastly different from the gl2.

One thing that I've noticed over the years is that some of the jumpiness can be attributed to the output device (monitor), cabling and other things...I don't know the technical aspects of it, but video signals can be sensitive to a lot of things, and I've seen the jumpiness of certain footage vary from set to set (and be almost non existent on a computer monitor).

Barry

"Several people with PAL GL2s have reported jerky images when panning in Frame mode, at their 25fps rate."

FILM at 24/25 fps has the same "jerkyness" .

" I wonder if true progressive-scanning cameras, like the AG-DVX100, have such a pronounced problem with jerkiness when panning"

it will have it's OWN jerkyness. remember this camera lays down to tape at 60i ( in 24p mode) .just like when film is transferred to NTSC it adds the 3:2 pull down .. this camera does the same 3:2 ( or the new 2:3) in the end it is 60i on tape ..and you view 60i watching the tape on a monitor ..

Tried it in daylight with the sharpness turned down, it's better but you still get a weird effect. But you're right about if you pan fast you don't notice it. To be honest I don't think I'll be using it, I prefer the normal mode, nice to have the option though.

Peter

One final note. I went to see "The Kid Stays in the Picture" yesterday. It's a documentary about the life of producer Robert Evans and made a lot of use of motion control on still photos, newspaper clips etc, in addition to vintage footage and some contemporary steadicammed interior and exterior shots of his house.

Looked like it was shot on 16mm, but maybe 35mm. Anyway I noticed that some of the shots of newspaper headlines, and high contrast bw photos panning across the screen strobed as bad (actually worse) than similar high-contrast images on my canon cameras, yet other motion control stuff of lower contrast had no such problem. It makes me think that perhaps these video cameras aren't that different from film in the first place, and perhaps contrast (and sharpness) is the real issue. I've noticed similar high contrast strobing in several feature films lately (on television), as well.

It's very easy with these camera's to make them strobe, by panning the camera against a varied background and viewing the results...and while this is not an unusual camera movement, pans like this often involve a moving subject, which typically remains relatively stationary in the frame. I encourage you to experiment with shots like these (following a person walking, a car, skateboarder) to see if you still notice the problem. Also, try Chris's recommendation and mount the camera on a tripod, and let someone move with in the frame..or just film an interview. See what you think.

If you don't like the look, then certainly don't use it. I'm a big proponent of the frame mode because I don't like the look of typical ntsc interlaced video(otherwise I'd probably own a sony). I guess I'm having a hard time believing that the pal camera is significantly different from the ntsc version, and is, in effect, unusable. In my experience, camera work is almost always the culprit. But regardless, I appreciate the discussion as I have learned alot from it. (In fact, the sharpness adjustment has virtually eliminated even the slightest amount of jitteryness with my camera). Thanks for bringing it up.

It's Labor Day here, so I guess I'll head off to work (my boss is an a**hole). cheers!

Barry

True I mean all my experimental stuff has been me just panning the camera across the garden. Also if you have a subject to focus on then it draws your attention away from the background so I guess that would help a lot and like you say they won't be moving that much in the frame. I'll see I will carry trying things out. I don't have a problem with the way Pal interlaced looks though and on the XM2 to it still has quite a filmic look to it.
Nice comment on the end by the way Barry, very out of context but very funny.