Rolling shutter and lightning footage

[Dan Robinson]

I have an important and legitimate concern about the rolling shutter issue that I still haven't seen a concrete answer about.

I am a storm chaser and many of my chaser colleagues are looking at the FX7 / HC7 / HC5 for their next camera. Lightning is one of the primary subjects that we shoot, and given the rolling shutter problems seen with early CMOS HD cameras, naturally we are concerned about the newer CMOS-based cameras exhibiting this same problem.

The reason this is important is that rolling shutter effectively kills all lightning video. The footage is unusable, with frames with lightning channels/flashes divided in half. Many chasers who bought the HC1 / 3 models were terribly disappointed with the cameras' total deficiency in capturing lightning.

For us, this is not an 'extraordinary circumstance' that we are putting the camera through just to 'expose its flaws'. Lightning is one of our main subjects, so I feel it is a legitimate question to pose. Has anyone tested the new CMOS based cameras with lightning, or even with a camera flash (which in theory should reproduce the same effect)?

We've done some serious digging and have not found an answer. Short of just buying one and finding a storm to shoot, there's no way to tell (and no retailer will take returns on a camera used on a storm shoot!).

Any info about this would be appreciated, as there are many storm chasers considering the FX7 / HC7 / HC5 but are reluctant because of the lightning/CMOS issue. A deficiency in the lightning capturing abilities of these cameras will be a deal-breaker. Not looking to stir up trouble or slam any particular camera model or manufacturer, just would like a simple 'yes' or 'no' on whether these cameras can do the job with storm footage.

[Serena Steuart]

Without the benefits of tests I'd expect the progressive exposure of a rolling shutter would make it quite unsuited to your application. Should be easy to test with a high speed flash illuminated target in the dealer's premises.

[Marcus Marchesseault]

I wish there was a simple yes or no answer. I am inclined to say "no, they don't work", but the FX7 appears to be four times faster with it's shutter than the other cameras. This is not confirmed, as far as I know, but the Sony literature seemed to indicate that the FX7/V1 have quadruple circuits to read the CMOS unlike other cameras. I'm assuming the other cameras are the consumer single-CMOS cameras. I'm guessing that you will not get the results you want, but try a test with the FX7 if you get a chance. I'm sure the single-CMOS cameras are still too slow.

[Dave Blackhurst]

Rolling shutter will likely still be an issue - tested with the HC7, and found about one out of 4 shots showed the effect with camera flash - usually only on the top or bottom 10-15% of the frame - on the HC1 I saw it split pretty evenly top and bottom. Not sure if the HC7 is better, but seemed like it might be.

Also another wedding videographer reported the rolling shutter with the V1 IIRC - it's an old post. He had sample stills showing the problem. That would mean the FX7 has the issue too.

In short, I don't think there's a solution to the problem - if we ever get any rain and thundershowers out here in Cali, I'll try shooting some to see what happens, but the way it's been, that may be a loooong time...

[Sergio Barbosa]

The V1 I have shows that same thing when there's a camera flash...only a portion of the picture is lit by the flash. For my work...weddings, corporate, etc..., this camera is amazing, but for your specific situation, I'd go for the Canon XH-A1.

[Chris Medico]

I agree with Sergio. Based on how my V1 responds to camera flashes I suspect it won't be usable for your application.

Maybe the FX1 or Z1 would be what you need if you are a Sony fan. Both are CCD based.

No current CMOS based video camera will likely be usable for your application due to the limitations of the technology. This isn't a flaw, its a characteristic of how the imager is read and is the same regardless of brand. CMOS has given us some good things such as longer battery life and great exposure latitude but we have had to pay for this with higher low light noise and the rolling shutter effect. In my application the camera works beautifully and I'm thrilled to have it.

As video processors get faster this technology may become usable to you at some point in the future. Right now, No.

Chris

[Dan Robinson]

Thanks for the info everyone - greatly appreciated and saved a lot of people from buying the wrong camera. I have an FX1 and it does just fine with lightning, so that's what I'll stick with and recommend to others.

[Chris Medico]

Originally Posted by Dan Robinson

Thanks for the info everyone - greatly appreciated and saved a lot of people from buying the wrong camera. I have an FX1 and it does just fine with lightning, so that's what I'll stick with and recommend to others.

The next chance I get to shoot some video of lightning here with my V1 I'll be happy to do it and let you know the result.

Chris

[Jack Kelly]

Hi there,

I'm very close to buying an HC7 but I'm also worried about the "rolling shutter" issue. In my case, a rolling shutter is bad news for my projects because I do match-moving in post-production (which is where the software analyses video footage and calculates the exact movements of the camera so that CGI elements can be inserted).

There is a simple test to determine if the HC7 has a rolling shutter. If anyone has an HC7, please can I ask you to do a simple test:

Please can you pan rapidly past an object with vertical lines (e.g. a door frame or a lamp post). On play-back, do the vertical lines look at all bent?

Here's an example of what happens when you do fast pans on the HV20 (which has a slow rolling shutter):

http://www.ssontech.com/content/crooked.mov

Many thanks,
Jack

[Sergio Barbosa]

Hi Jack,
As far as I know every CMOS camera uses rolling shutter. I believe it's inherent to the technology.
Those bent vertical lines appear on the V1 (not so drastically as in your video, i think) but I read somewhere that the engineers used some technique to minimize that.
I suppose the HC7 won't be any better than the HV20.

[Jack Zhang]

Originally Posted by Jack Kelly

Hi there,

I'm very close to buying an HC7 but I'm also worried about the "rolling shutter" issue. In my case, a rolling shutter is bad news for my projects because I do match-moving in post-production (which is where the software analyses video footage and calculates the exact movements of the camera so that CGI elements can be inserted).

There is a simple test to determine if the HC7 has a rolling shutter. If anyone has an HC7, please can I ask you to do a simple test:

Please can you pan rapidly past an object with vertical lines (e.g. a door frame or a lamp post). On play-back, do the vertical lines look at all bent?

Here's an example of what happens when you do fast pans on the HV20 (which has a slow rolling shutter):

http://www.ssontech.com/content/crooked.mov

Many thanks,
Jack

I have a video of the bars of the walkway on a bridge flying by at high speeds at the beginning of this video:

http://stage6.divx.com/user/jackvanc...httime-(720p60)

I hope this would show the speed of the rolling shutter.

[Jack Kelly]

Originally Posted by Jack Zhang

I have a video of the bars of the walkway on a bridge flying by at high speeds at the beginning of this video:

http://stage6.divx.com/user/jackvanc...httime-(720p60)

I hope this would show the speed of the rolling shutter.

Jack, thanks loads for sharing that video with us - it looks great. Man, you've gotta love that 720/60p-on-the-web look. Eat dust, YouTube.

Anyway... from what I can tell, that video provides good evidence to support the hypothesis that the HC7 either has a "global shutter" (i.e. it reads every pixel on a field at the same timepoint) or it has a very swift rolling shutter. Maybe my eyes are deceiving me but I couldn't see any "rolling-shutter" distortions in the footage of the railings and support rods. Shooting railings from a moving car is an excellent test for rolling shutter effects because the horizontal portion of the railings gives us an accurate orientation reference (i.e. it should be horizontal). If the video of the vertical bars supporting the horizontal railing aren't perpendicular to the railing then we know that the camera is distorting the image. But, apart from some barrel distortion due to the wide lens, I couldn't see any geometric distortions. Can anybody else see any distortions in this video?

Thanks again for posting that video,
Jack

[Piotr Wozniacki]

I second that - perhaps some distorsion can be found when examining frame-by-frame, but the vido looks great! What shutter speed was used in the first portion?

[Jack Zhang]

The whole video is at a shutter speed of 1/60.

[Jack Kelly]

Hi Jack,

Going a little off-topic... but how did you do the conversion from 1080/60i to 720/60p? Did you use AviSynth?

Thanks,
Jack