This IS the Avid L2: [Avid-L2] Re: 60Hz like hum line in multiple Red Epic Cameras?

Thursday, June 13, 2013

[Avid-L2] Re: 60Hz like hum line in multiple Red Epic Cameras?

There is both a audio and tc offset function on the Pix. Either it was ignored or incorrectly set.

--- In Avid-L2@yahoogroups.com, Jim Feeley <jfeeley@...> wrote:
>
> > Pix recorders for the offline media that turned out to be 2 frames off.
> Hmm. There was a -2 frame TC offset bug that Sound Devices fixed over a year ago in a firmware update.
> Also, you can adjust the PIX sync offset of audio to compensate for a camera's picture conversion. But there could have been another issue and that's not what you're asking about...
>
>
> > The colorist did mention Reds having some issues with HMI lights.
> If you shoot under HMIs and don't use an absolute shutter speed (as you get with RED's "normal" mode), but instead use RED's "relative" mode, then you can cause shutter to generate something that looks like a roll bar (same with other rolling-shutter cameras). Though I've only seen those lines roll up, not down as I think you said yours are doing... and that was with RED cameras at HMI-hostile framerates and shutter angles (like 23.98 + 180-degree shutter). At least, that's how it was explained to me... I could have this wrong, but I don't think I do.
>
> Could be a lot of things. Too bad it wasn't caught and fixed during the shoot.
>
> Jim Feeley
> jfeeley@...
>
>
>
> On Jun 12, 2013, at 10:21 PM, johnrobmoore wrote:
>
> > It was a standup performance on a theater stage. They shot 29.97P with an ISO of 1600, which is quite high but we think they irised down the cameras to get more depth of field so focus wasn't such a problem. According to the offline editor the head on camera with a medium waste shot would go out of focus if the performer moved back 6 inches to a foot. Sounds like a real cameraman nightmare hence the high ISO to compensate for the irised down lens to improve DOF. Really the wrong tool for the job but I guess it saves them money in production. I don't know what shutter angle but the colorist who looked at the footage thought ground loop and he has more experience with Red footage so I would think he'd have brought up shutter angle if it seemed like the culprit. The colorist did mention Reds having some issues with HMI lights. Given this crew couldn't even get us down converts that are in sync to the Red Raw files nothing surprises me anymore.
> >
> > --- In Avid-L2@yahoogroups.com, Benjamin Hershleder <Ben@> wrote:
> > >
> > >
> > >
> > > I'm curious:
> > > - what lights are they using (HMI?),
> > > - what frame rate are they shooting,
> > > - what's the shutter speed, and
> > > - what's the shutter angle?
> > >
> > > Possibly one of those questions will lead to the solution (?)
> > >
> > > B
> > >
> > > ----
> > > Benjamin Hershleder
> > > Book: http://tinyurl.com/avidmc-book
> > > Site: http://ContactBen.com
> > >
> > > Wear It In Post!
> > > Fun T-shirts, mousepads, mugs & more
> > > for Post Production Professionals
> > > http://www.WearItInPost.com
> > >
> > >
> > > On Jun 12, 2013, at 6:49 PM, John Moore wrote:
> > >
> > > > On the mulitcamera Red Epic stage shoot I've been helping on they finally brought in a Resolve Colorist and we found that there appears to be a 60 Hz like hum line traveling from top to bottom in multiple cameras all Red Epics. A ground loop was suggested by the colorist. This was a multicam shoot with external Pix recorders for the offline media that turned out to be 2 frames off, but that's another story. I'm curious how a ground loop/floating ground could effect the internal Red feed from the sensor to the Raw file. Is the ground loop actually effecting the sensor itself which then feeds into the Raw file. The line is thinner that a typical 60 hum bar but it is a horizontal line that brightens up the picture as it passes through. It's mostly noticeable on medium grey pillars in the back ground. We see it in multiple cameras. It sounds like there a plenty of ground loop sources with external Pix recorder and feeds to director's monitors
> > > > etc... If it's not a floating ground I'm wondering it maybe some new LED style lights might have been used or some other new exotic lighting source that might have created the problem. Anybody seen anything like this?
> > > >
> > > > John Moore
> > > >
> > > > Barking Trout Productions
> > > >
>