Sony EX1 Severe LongGop Problems

[Richard Ladkani]

The motion blur was due to the fact that the shutter was turned OFF. When on later tests the shutter was ON at 1/50th of a second everything was fine.
Best
Richard

https://www.richardladkani.com

[Steve Brown]

Hey guys,

I wonder if someone can clarify this for me. I was considering buying an EX-1 or an EX-3 for use as a POV camera, but this business of motion artifacts due to long GOP scares me a bit. Do you mean you have to use a particular shutter speed to avoid these artifacts? In my world, shutter speeds are not used for that purpose and I’d hate to have to use a 1/50th when I want 1/30th, 1/48th or 1/60th, etc.

Am I missing something here?

Steve Brown
10-20 Productions

[Craig Seeman]

There are no motion artifacts that I’ve ever seen with 35mbps VBR XDCAM codec. It’s very hard codec to break. I’ve shot rippling water, leaves blowing in the wind, fireworks, tennis players, all look great. Don’t believe misinformation.

In some cases there can be rolling shutter on camera flashes. You can get “bending” if tracking a fast moving object with a very fast pan due to CMOS chip scan. I don’t find that a problem and neither do my clients. CMOS has pluses and minuses just as CCD chips do.

[Steve Brown]

Craig,

Are you referring to the XDCam, XDCam HD or XDCam EX? I have never heard of this problem with XDCam or XDCam HD, but I seem to be hearing a lot about this problem with the EX versions of XDCam. From what I am hearing, it sounds as though the problem is the internal long GOP recording process – similar to motion artifacts seen with HDV.

Keep in mind, I have not seen this problem with the Sony EX cameras. I have only seen those cameras a couple of times and there was not enough motion to be a problem in either case. I have seen the problem with JVC 250 cameras, however… and I understand that this problem is essentially expected in the HDV format.

Someone please set me straight if this is not correct!

Steve Brown
10-20 Productions

[Craig Seeman]

[Steve Brown] “Someone please set me straight if this is not correct!”

Not correct. I own an EX1 and I’ve shot many things that would cause HDV to crumble. EX is an XDCAM camera using the same 35mbps VBR codec. It’s wrapped in MP4 instead of MXF but that’s just a wrapper, not the codec.

Personally I think a lot of people who use EX series who make such claims are wrongly identifying other issues as codec issues. Rippling water and blowing leaves are about the toughest thing you can throw at a GOP codec and that doesn’t even have a hint of breaking. In fact I think many people don’t even understand what “motion” is to a codec. Rippling water is constant and rapid change from frame to frame and can be across the entire frame depending on framing. Motion does NOT have to be spinning the camera around.

[Steve Brown]

Craig,

Thanks for the info. I guess I need to see the camera myself and use it enough to see if problems I’ve heard about have any validity. I have seen some problems with the HDX900s also and careful adjustment of detail coring has helped tremendously with things like trees with blowing leaves and other high detail subjects.

Do the EX series cameras have adjustment for “detail coring” and “level depend”?

Steve Brown
10-20 Productions

[Andrea Chung]

excerpt from Wikipedia that explains it re: rolling shutters:

As opposed to a global shutter, where the whole of the sensor is presented with light at once, resulting in the whole of the frame being captured simultaneously, with a rolling shutter, the image is captured sequentially in thin rows from top to bottom, one after the other, over the course of a single frame.

Rolling shutters have the potential to frustrate videographers by creating rolling shutter “artifacts” due to the possibility of the camera moving during the time when the top and bottom of a single frame are captured. This can result in issues such as “skew”, “partial exposure” and what is colloquially known as the “Jellocam” phenomenon.

& this article:

https://dvxuser.com/jason/CMOS-CCD/

[Sean Mcphillips]

‘The motion blur was due to the fact that the shutter was turned OFF. When on later tests the shutter was ON at 1/50th of a second everything was fine.
Best
Richard’

So, does this solve the original problem then?

Just wondering.

If so, can we have a reference to it at THE TOP of this thread FCOL?

Thanks ;~)

Sean McPhillips

[Richard Ladkani]

Hi,

I was asked to clarify this thread at the top.

The problem has been solved. There is no Long Gop Issue or motion blur problem. The shutter of the camera was turned OFF which means it was at 1/25th. When turned on to 1/50th all problems are solved. Fact is: YOu have to turn on the shutter manually when shooting 25p! Very important.

Best wishes
Richard

https://www.richardladkani.com

[Steve Brown]

OK, so here is the problem I am having with all of this. Does this mean that one is forced to shoot with a particular shutter speed in order to avoid these problems? That seems a little crazy to me. If I’m shooting at 24 fps (progressive), I generally have a 180 degree shutter angle equivalent to 48 fps. If I’m shooting at 30 fps (progressive), I do the same thing, so my equivalent shutter speed will be 60 fps. (OK, in reality the frame rates are fractional… but they are close to those rounded numbers – actual frame rates would be 23.976/47.952 and 29.97/59.94.)

I wouldn’t want to be forced to shoot at a shutter speed of 1/50th (or any specific frame rate) just to avoid artifacts. And what if I want to shoot for slo-mo? Normally, I’d shoot at 60 fps (progressive) with or without a 180 degree shutter angle. Is that going to be a problem also? Or will that faster shutter speed help to alleviate the problem as well?

Feel free to set me straight if I am misinterpreting any of this. These little quirks are why I have stayed away from the smaller cameras in the past, but I’d sure like to have a quality HD camera to carry on hiking trips, kayaking trips or other adventures where a full sized HD camera just isn’t practical.

Steve Brown
10-20 Productions