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What Causes This?

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alec gitelman
What Causes This?
on Nov 9, 2010 at 7:36:53 pm

Hi,

this is a from a very quick pan, totally unusable shot, but I still wonder what's making it look like that. I'm guessing it's a combination of both rolling shutter and breaking the codec, but I'd like to know what to avoid if I were to be pushing the capabilities of the camera in a similar situation.

Can anyone point out what exactly is happening?

Thanks.





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Craig Seeman
Re: What Causes This?
on Nov 9, 2010 at 7:48:48 pm

What frame rate, shutter speed?
A single frame can't give us an idea how fast the pan is. Who's going to see a single frame on a whip pan?
If it's a slower pan than the above information might help.
That the image is blown out doesn't help either.



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alec gitelman
Re: What Causes This?
on Nov 9, 2010 at 7:57:35 pm

this may give an idea of how fast the pan is.
720p24
shutter - i'm guessing 1/48 but i wouldn't say for sure.









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Craig Seeman
Re: What Causes This?
on Nov 9, 2010 at 8:04:13 pm

There are professional cinematographer guidelines on panning and camera movement at 24fps. Fast pans aren't going to look good at that frame rate regardless of camera. This is why some people shoot sports at 60fps for example.

Shutter speed also impacts on motion blur and the more blur the likely more work for the codec with fast motion.

That your image is blown out in some areas and very dark in others just makes it that much more problematic.

If you're shooting at 24fps pan slowly. Consider polarizer or some other method to knock down that contrast.



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alec gitelman
Re: What Causes This?
on Nov 9, 2010 at 8:16:31 pm

I understand, in this case I was just swinging the camera around from shot to another.

I see the skew. I'm curious what causes those lines extending from the silhouettes appear.



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Craig Seeman
Re: What Causes This?
on Nov 9, 2010 at 8:18:05 pm

Probably the radical change between dark to blown out on the codec with fast motion.



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David Jones
Re: What Causes This?
on Nov 9, 2010 at 8:39:06 pm

If I remember correctly, according to the ASC, [shooting @24fps] an object should take AT LEAST 8 seconds to pass from frame edge to frame edge during a pan.

Dave J


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Noah Kadner
Re: What Causes This?
on Nov 10, 2010 at 2:48:56 am

Experience tells us it's a lot easier to make an iffy looking frame than a nice looking one. Tripods or at least a shoulder mount and taking it easy with your pan speed will go a long way.

Noah

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Bob Hayes
Re: What Causes This?
on Nov 10, 2010 at 11:39:03 pm

Alec

My guess is it is a LOG GOP artifact. One of the downsides of the EX1 is how it compresses the image and one of the results is a wavy vertical line when panning. Try shooting telephone poles from a driving car to really see the issue. I haven't faced the problem but it occasionally rears its head. Recording onto an external drive eliminates the problem.

Bob Hayes
DP
Los Angeles


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Craig Seeman
Re: What Causes This?
on Nov 10, 2010 at 11:55:39 pm

Bending lines is due to CMOS rolling shutter, not the codec.



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Bob Hayes
Re: What Causes This?
on Nov 13, 2010 at 6:33:21 pm

Of course. I missed that in your earlier post. I have same problem but really exaggerated on my Contour camera.

Bob Hayes
DP
Los Angeles


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