Horizontal Blue Stripes? Please help if you can!

[Fly Reeves]

NOTE: Posted after long shoot day - they're actually VERTICAL stripes. Thanks.


I'm currently shooting overseas and I've just noticed an issue with the AF100 that's mind boggling and a bit frightening. Essentially thick, vertical blue stripes appear in darker parts of the frame. They always seem to be in the same spots - about a third of the way from the left edge of the frame and closer to the right edge of the frame. These will show up w/ hard edges on occasional frames and then go away. The effect ends up looking like a bit of an odd pulse or flicker. It doesn't always happen and we seem to have mitigated it w/ some fiddling.

We're shooting 1920x1080 24p. Various types of glass on PL mount adapter and one M4T lens all have exhibited this issue at various times - we're mostly using an Angenieux zoom so I'm mostly looking at footage w/ that. We're shooting these scene file settings that we gleaned from this board:

detail -7
v detail -7
coring +2
m ped -2
chroma level -2
gamma cine-v
matirx norm 2
DRS off

I'm attaching some jpeg frame grabs here. Two are consecutive frames where you can see a clean image and the next frame that exhibits the stripes (middle of black jacket and right shoulder of green jersey). I'm also posting a third still where you can see the stripes a bit more clearly. I'm wondering if these stills will be compressed in the post, but you should get the idea regardless. I'm also posting a clip here: http://www.mediafire.com/?2u1zmcwo8rbdf

It's very slow to upload so it may not be there for a while. We've been fighting with this for a day now - it's my first shoot w/ the camera and the DP's been playing with the camera for a few weeks and hadn't noticed this before. Unfortunately we're overseas shooting a doc pitch tape on spec - trying to raise funds for a feature. I'd say I can likely cut around the worst of this and use the problematic footage when absolutely necessary but if there's anything you guys can suggest I'd really appreciate it.

We're shooting to SD card - I wonder if this is a symptom of the internal codec and if we'd avoid it shooting to an external recorder? It seems too bad of a issue to be that but I'm stumped. Bad sensor? Some dumbass user error? You can see from the clips we're shooting sports and are pushing things a bit - I don't mind the normal video noise but what I'm seeing here is a new beast as far as I'm concerned. I scoured these boards reading virtually everything before we committed to the camera for this shoot and haven't heard anything like this mentioned. I'm loving what I see from this camera when it's not exhibiting this!

Thanks,

David

 

[grimrebes]

I watched your clip... Did you have a lens hood on your glass? My guess is that the little bit of blue I saw looks like lens flare.

 

[broughtonfilm]

I watched your clip... Did you have a lens hood on your glass? My guess is that the little bit of blue I saw looks like lens flare.

Not a lens flare in my opinion. Watch his video frame by frame, you can clearly see a regular pattern of those blue stripes. If it is a lens flare... any chance that your matte box had a gap that equals the width and pattern of your stripes? That would explain their regularity.

To me it looks more like a defective unit or maybe some compression artifact, I have not noticed anything like that in my footage so far. Could it also be caused by some strange frequencies interference (scan and light flickering). You said your shoot was abroad - are the sync scan settings correct, any chance this is caused by the flickering lights that light the stadium? Strange.

 

[Fly Reeves]

Thanks for watching the clip broughton. I agree that it's not a lens flare as we've consistently seen these stripes in the exact same spot on the frame and they have appeared in lighting set ups vastly different from what you see posted above . My number skills aren't what they used to be so if you can discern the pattern I'd love to know.

I do wonder about the frequency interference - we're shooting in Israel. I'm not sure about the correct sync scan settings, but I know the DP has adjusted and that did seem to mitigate the anomaly some (as well as get rid of other more normal scan flicker type stuff).

Thanks!

David

 

[Fly Reeves]

Now that I look at the clip before a long shoot day the pattern of the blue lines is definitely: Off, Off, On, On, Off, Off, On, On, etc... Crazy.