Rolling shutter on EX?

Bob Hart · February 19th, 2009, 07:09 AM

I have just been looking at some clips shot using an EX1 as a fixed overhead camera on a Manfrotto rig facing directly down over a demon drummer for a tutorial video.

A guy going nuts with drumsticks has to be about the best test ever. If there is an artifact there, I cannot see it.

A side note. If you are mounting the EX1 overhead facing directly down, especially if you have a roomful of redheads, periodically check the back of the camera. It seems to get frighteningly hot in this position and it cannot be good for it.

David Issko · February 19th, 2009, 02:19 PM

unless you shoot somewhere that there are photos being taken with flash. rolling shutter really shows its not so pretty head.

best wishes

Jay Gladwell · February 19th, 2009, 02:57 PM

Can't speak for the EX1, but our EX3 has recorded images while electronic flashes are being used and we have not seen any problems.

Bob Grant · February 20th, 2009, 04:29 AM

Much of both the FUD and denial of this issue could be avoided if people made the effort to understand how a CMOS sensor differs from a CCD sensor. Sony certainly are quite clear on this issue, every EX1 and EX3 camera uses the same designed CMOS sensor. Everyone of the EX1/3 cameras will perform identically unless it has a defect, in regard to how the sensor is scanned.

The use of roller blind shutters predates the invention of the video camera by decades, skewing of vertical lines moving accross the frame and the elongation of carriage wheels is a documented fact known before any of us here were born.

Roller blind shutters

Put simply a CMOS sensor does not 'expose' the whole frame at once. Each roll of pixels is exposed and scanned in sequence from top to bottom. This takes a finite time just as the roller blind shutter took a fixed time to expose the film from top to bottom. In the case of the EX cameras it seems to be 1/60th of a second. This is regardless of shutter speed. Higher shutter speeds will make the effect more obvious by reducing motion blur which typically masks the skew.

There is a significant upside to the use of a CMOS sensor over a CCD. The analogue signals from the photodetectors is more directly routed to the analogue to digital converter(s). The signal gets there with less distortion and noise i.e. a better picture for your money.

So we're all left with a (hopefully) informed choice. Is a rolling shutter going to prevent us from using this camera or would we prefer better quality images for our money. Indeed for some the effect of a rolling shutter will be a show stopper. Sony know this, that's probably one reason they make cameras with CCDs.

What I don't understand is why the issue of flashes exposing only part of a frame is bought up all the time. It's a piece of cake to fix if it does happen. Skew is impossible to fix however but it's rarely an issue that needs fixing outside of specialist scenarios and even then the limitations of the XDCAM encoding system are likely to be an even bigger issue.

Steve Phillipps · February 20th, 2009, 05:06 AM

Quote:

Originally Posted by Bob Grant

Indeed for some the effect of a rolling shutter will be a show stopper. Sony know this, that's probably one reason they make cameras with CCDs.

That's hitting the nail on the head, if there were no problems then all cameras would be using CMOS, but the serious cameras all have CCDs (with the very special exception of the Phantom HD).

It's common sense that if a product comes along that has higher specs AND a lower price than what's currently available then there must be a catch. This is what happened with the EX1, on paper it blows the Sony F900 out of the water (full raster, plus overcranking, OK the codec is not so robust) but at a fraction of the price. Same goes for the RED, Ikonoskop etc., if it sounds too good to be true then it is.

Don't shoot me down, just my thoughts. And I have tried the EX1 and 3 and both instances when filming flying birds I'm still immediately seeing motion issues.

Steve

Jay Gladwell · February 20th, 2009, 06:10 AM

Quote:

Originally Posted by Steve Phillipps

And I have tried the EX1 and 3 and both instances when filming flying birds I'm still immediately seeing motion issues.

And this is a perfect example of why I say it's a user issue. I've seen footage of flying birds (and aircraft) shot with the EX1 and EX3 that doesn't have any motion issues. How else can it be explained, other than the user?

Steve Phillipps · February 20th, 2009, 06:15 AM

Well there's nothing the user can do unfortunately, if the birds dives you can't shout at it to tell it do it slowly!

The reason I raise it is that I usually use Varicam, HDCam and formerly Super 16 and never seen it as an issue. Nor have I seen it as an issue on the Phantom HD (which also has a rolling shutter, but it's a very different beast of course).

Also in terms of "user issues" I've never had any complaints after 15 years work, including prime-time network series for the BBC NHU.

Steve

Bob Grant · February 20th, 2009, 08:31 AM

Flying birds or aircraft are very unlikely to show the effect of the EX's rolling shutter.
Just because something is moving quickly has no bearing on you seeing it or not.

Here are some examples of rolling shutter induced skew:

http://web.tiscali.it/rudiversal/ima...fekt%20HC1.JPG

Easy enough to reproduce the exact same thing with an EX1 or EX3 if you're hell bent on seeing it. Drive down a street with the camera pointed out the window, a fast shutter speed helps. You'll notice that verticals close to the camera, for example roadside power poles are skewed away from the direction of travel. Vertical objects further away from the camera display less skew. That's because their rate of motion across the frame is slower than the closer objects. That explains why it's very hard to see in planes and birds.

It also explains why the effect is almost impossible to correct as the amount of deskewing required depends on the distance of each object in the frame from the camera. Even more of an issue is it introduces problems with occlusion.

Of course the above is an unusual shooting scenario and it's therefore a problem that thankfully most of us can remain oblivious to. Even when it does happen it's unlikely it'll be so obvious to the viewer as to be offensive. I've got footage from another camera shot out the window of a train. The closeby power poles are seriously skewed but no one notices as they're too attracted to the scenary.

Jay Gladwell · February 20th, 2009, 09:23 AM

Quote:

Originally Posted by Bob Grant

Flying birds or aircraft are very unlikely to show the effect of the EX's rolling shutter.
Just because something is moving quickly has no bearing on you seeing it or not.

Agreed! But other posters would have us thinking otherwise.

Quote:

Originally Posted by Bob Grant

Here are some examples of rolling shutter induced skew:

http://web.tiscali.it/rudiversal/ima...fekt%20HC1.JPG

For some reason I can't access the web site--tried two computers and two different browsers.

Quote:

Originally Posted by Bob Grant

Easy enough to reproduce the exact same thing with an EX1 or EX3 if you're hell bent on seeing it. Drive down a street with the camera pointed out the window, a fast shutter speed helps. You'll notice that verticals close to the camera, for example roadside power poles are skewed away from the direction of travel. Vertical objects further away from the camera display less skew. That's because their rate of motion accross the frame is slower than the closer objects. That explains why it's very hard to see in planes and birds.

It also explains why the effect is almost impossible to correct as the amount of deskewing required depends on the distance of each object in the frame from the camera. Even more of an issue is it introduces problems with occlusion.

I'm talking about footage of birds and planes that fill the frame and have both foreground and background imaging. No skewing.

Here's a frame of a race car that is skewed. Guess what camera was used. You can read about it here:
http://maisonbisson.com/blog/post/10...er-distortion/

Steve Phillipps · February 20th, 2009, 09:42 AM

I've said time an again after testing EX1/3 that I'm not saying it is skew, but it's definitely something
Steve

Jay Gladwell · February 20th, 2009, 09:53 AM

Steve, I missed this post somewhere along the way.

Quote:

Originally Posted by Steve Phillipps

... but the serious cameras all have CCDs...

I cannot agree with that statement. Suggesting that any camera that uses a CMOS sensor is not a "serious" camera is terribly misleading and erroneous.

Steve Phillipps · February 20th, 2009, 10:11 AM

What I mean is all the cameras that are considered top-grade broadcast and cinematic cameras - so Sony F900, F23, F35, Panavision Genesis, Panasonic HPX 2700, 3000, 3700. There are specialist cameras like Phantoms with CMOS, and fringe ones like the RED, but the first ones are the mainstream high end cameras from high-end docs to Hollywood and there ain't a CMOS in sight.
Steve

Buck Forester · February 20th, 2009, 10:32 AM

Hmmm... I read about A-list Hollywood directors, shooting Hollywood movies with A-list actors for major theatrical releases, on RED ONE cameras. Am I missing something about there being "ain't a CMOS in sight" on serious high-end projects? Did RED sneak some CCDs in some of their cameras? :)

Steve Phillipps · February 20th, 2009, 10:35 AM

As I said, they are there on the fringe, check my post.
Steve

Jay Gladwell · February 20th, 2009, 10:51 AM

Quote:

Originally Posted by Steve Phillipps

There are specialist cameras like Phantoms with CMOS, and fringe ones like the RED, but the first ones are the mainstream high end cameras from high-end docs to Hollywood and there ain't a CMOS in sight.
Steve

That simply isn't true. The Discovery Channel has accepted the EX cameras for 100% of programming. If the The Discovery Channel isn't "high-end", then I don't know what is.

February 19th, 2009, 07:09 AM	#1
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Rolling shutter on EX? - Panic not. I have just been looking at some clips shot using an EX1 as a fixed overhead camera on a Manfrotto rig facing directly down over a demon drummer for a tutorial video. A guy going nuts with drumsticks has to be about the best test ever. If there is an artifact there, I cannot see it. A side note. If you are mounting the EX1 overhead facing directly down, especially if you have a roomful of redheads, periodically check the back of the camera. It seems to get frighteningly hot in this position and it cannot be good for it.

February 19th, 2009, 02:19 PM	#2
David Issko Major Player Join Date: Jul 2008 Location: Melbourne, Australia Posts: 393	unless you shoot somewhere that there are photos being taken with flash. rolling shutter really shows its not so pretty head. best wishes __________________ David Issko Edit 1 Video Productions

February 19th, 2009, 02:57 PM	#3
Jay Gladwell Join Date: Jul 2002 Posts: 1,244	Can't speak for the EX1, but our EX3 has recorded images while electronic flashes are being used and we have not seen any problems.

February 20th, 2009, 04:29 AM	#4
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	Much of both the FUD and denial of this issue could be avoided if people made the effort to understand how a CMOS sensor differs from a CCD sensor. Sony certainly are quite clear on this issue, every EX1 and EX3 camera uses the same designed CMOS sensor. Everyone of the EX1/3 cameras will perform identically unless it has a defect, in regard to how the sensor is scanned. The use of roller blind shutters predates the invention of the video camera by decades, skewing of vertical lines moving accross the frame and the elongation of carriage wheels is a documented fact known before any of us here were born. Roller blind shutters Put simply a CMOS sensor does not 'expose' the whole frame at once. Each roll of pixels is exposed and scanned in sequence from top to bottom. This takes a finite time just as the roller blind shutter took a fixed time to expose the film from top to bottom. In the case of the EX cameras it seems to be 1/60th of a second. This is regardless of shutter speed. Higher shutter speeds will make the effect more obvious by reducing motion blur which typically masks the skew. There is a significant upside to the use of a CMOS sensor over a CCD. The analogue signals from the photodetectors is more directly routed to the analogue to digital converter(s). The signal gets there with less distortion and noise i.e. a better picture for your money. So we're all left with a (hopefully) informed choice. Is a rolling shutter going to prevent us from using this camera or would we prefer better quality images for our money. Indeed for some the effect of a rolling shutter will be a show stopper. Sony know this, that's probably one reason they make cameras with CCDs. What I don't understand is why the issue of flashes exposing only part of a frame is bought up all the time. It's a piece of cake to fix if it does happen. Skew is impossible to fix however but it's rarely an issue that needs fixing outside of specialist scenarios and even then the limitations of the XDCAM encoding system are likely to be an even bigger issue.

February 20th, 2009, 06:15 AM	#7
Steve Phillipps Inner Circle Join Date: Apr 2006 Location: Wales Posts: 2,130	Well there's nothing the user can do unfortunately, if the birds dives you can't shout at it to tell it do it slowly! The reason I raise it is that I usually use Varicam, HDCam and formerly Super 16 and never seen it as an issue. Nor have I seen it as an issue on the Phantom HD (which also has a rolling shutter, but it's a very different beast of course). Also in terms of "user issues" I've never had any complaints after 15 years work, including prime-time network series for the BBC NHU. Steve

February 20th, 2009, 08:31 AM	#8
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	Flying birds or aircraft are very unlikely to show the effect of the EX's rolling shutter. Just because something is moving quickly has no bearing on you seeing it or not. Here are some examples of rolling shutter induced skew: http://web.tiscali.it/rudiversal/ima...fekt%20HC1.JPG Easy enough to reproduce the exact same thing with an EX1 or EX3 if you're hell bent on seeing it. Drive down a street with the camera pointed out the window, a fast shutter speed helps. You'll notice that verticals close to the camera, for example roadside power poles are skewed away from the direction of travel. Vertical objects further away from the camera display less skew. That's because their rate of motion across the frame is slower than the closer objects. That explains why it's very hard to see in planes and birds. It also explains why the effect is almost impossible to correct as the amount of deskewing required depends on the distance of each object in the frame from the camera. Even more of an issue is it introduces problems with occlusion. Of course the above is an unusual shooting scenario and it's therefore a problem that thankfully most of us can remain oblivious to. Even when it does happen it's unlikely it'll be so obvious to the viewer as to be offensive. I've got footage from another camera shot out the window of a train. The closeby power poles are seriously skewed but no one notices as they're too attracted to the scenary.

February 20th, 2009, 09:42 AM	#10
Steve Phillipps Inner Circle Join Date: Apr 2006 Location: Wales Posts: 2,130	I've said time an again after testing EX1/3 that I'm not saying it is skew, but it's definitely something Steve

February 20th, 2009, 10:11 AM	#12
Steve Phillipps Inner Circle Join Date: Apr 2006 Location: Wales Posts: 2,130	What I mean is all the cameras that are considered top-grade broadcast and cinematic cameras - so Sony F900, F23, F35, Panavision Genesis, Panasonic HPX 2700, 3000, 3700. There are specialist cameras like Phantoms with CMOS, and fringe ones like the RED, but the first ones are the mainstream high end cameras from high-end docs to Hollywood and there ain't a CMOS in sight. Steve

February 20th, 2009, 10:32 AM	#13
Buck Forester Major Player Join Date: Feb 2008 Location: California Posts: 230	Hmmm... I read about A-list Hollywood directors, shooting Hollywood movies with A-list actors for major theatrical releases, on RED ONE cameras. Am I missing something about there being "ain't a CMOS in sight" on serious high-end projects? Did RED sneak some CCDs in some of their cameras? :)

February 20th, 2009, 10:35 AM	#14
Steve Phillipps Inner Circle Join Date: Apr 2006 Location: Wales Posts: 2,130	As I said, they are there on the fringe, check my post. Steve