heavy pixellation after photographer flashes
 

Hi: In looking over wedding footage that I've shot with the FX1 and captured natively via FCP, I've been noticing a large amount of pixellation (blockiness) that affects my picture in the frames immediately following the flash from a photographer's flashbulb ... these flashes really seem to send the camera reeling and it takes a moment to recover a decent picture.

Anyone else notice this? I'm guessing this results from the HDV mpeg?

Yep, I've noticed this, and yep, it's MPEG related.

MPEG encodes the changes between frames for most frames, so when the flash comes and goes, the pixels change radically and there aren't enough bits to encode the detail well. Lighting bolts cause the same type of effect. You can occasionally see this on digital cable programs which encode using MPEG also.

Bill

Deinterlace it should get rid of most of that.

Thanks guys ... Ryan, I assume you're referring to the deinterlace filter in FCP? I did try that on a test clip and it didn't seem to have much effect ... perhaps it would work for stills?

Bill, did you ever find a workaround?

No, there really isn't a workaround. It's just that the footage ends up with visible macroblocks for a reasonable portion of the GOP = around a half a second. If you're going to be shooting something where you know there is nonstop flashbulbs, strobelights, or lighting, you might want to switch to plain old DV as it might be better (DV being an intraframe codec rather than the interframe codec of HDV).

And I don't know how any deinterlacing would fix things, as it shows up even in progressive HDV modes.

Bill

I've seen something like that on performance video I shot where there was a bright gun flash. It looks really ragged if you view still frames, but doesn't particularly show up when watching the video.

Thanks Bill. So I suppose this is the same for any HDV cam ... the new cams (V1, Canon A1) probably don't handle this any better than the FX1, eh?

It's only 1 frame Dave, don't worry about it, you will never see it watching it at normal speed, and I rarely see it happens, it will not happens at every flash, but if it bothers you then just cut that frame, it is right after the flash and so people shouldn't noticed that jump, but it has never interfere with my editing at all.

Thanks Khoi ... it's fine most of the time, but for the procession, and when the bride and groom are introduced into the reception, there's usually dozens if not hundreds of flashes going off -- which translates into many pixellated frames ... perhaps for those times I'll switch to DV wide mode. Have you had a chance to notice whether the Canon A1 has the same reaction to flashes?

BTW -- your old camera is working great, thanks.

The problem that I notice is that it isn't always just the one frame. It's the single frame and a number of frames afterwards, because not only does that frame have problems with motion prediction but the rest of the GOP does also. And as some others have noticed, it can be particularly bad if a stream of photo flashes are going off in sequence. The same thing happens with strobe lights in concerts.

Don't get me wrong, I love my Z1, but I keep an eye out for very sudden flashes...

Bill

I don't see this as a problem at all Dave, I shoot wedding just like you and there are tons of flashes at the intro with my brides too and it never seems to be a problem, I just pull out an intro and there were 6 flashes within a second or 2 or so and did not see any, like I said you will see it once in awhile but not everytime, this has never been a problem for me. Don't switch to DVCAM, this camera does not look good in DVCAM mode, I had compared it with my DSR300 and VX2000 back when I just purchased it and its footages downconvert looks better than DSR300 under good light, but if you shoot in DVCAM or DV then it don't even look as good as my VX2000 so don't mess with it, stay in HDV.
I have not pay any attention to the flashes with the A1 because it was not a concern but I would imagine that it would be the same as Sony because both use HDV codec.

We use the canon HV10 while we do photo shoots and have strobe flashes going off. The effect it has on the video is much much worse until we deinterlace.

...You're probably doing something weird anyway. Like blending frames around or something.

Not that im aware of. Why would you assume that?

Because deinterlacing doesn't get rid of mpeg artifacts. Unless the artifact is in one field only and the deinterlacer happens to eliminate that exact field.