Rolling Shutter CMOS Artifacts

A question for those familiar with the RED camera.

With so much technology in this cam, why elect a rolling shutter configuration?
 
dvInsight said:
I posted the following over at DV Forums following a private email I sent to a friend on the East coast and you would have thought I said something about their first born:

<SNIP>
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I saw that, I'll never understand why people get so defensive about this stuff, you'd almost think you were insulting their favorite sports team from some of the reactions. I love my DVX, but I'm also aware of it's shortcomings and can discuss the pros and cons objectively.

This is just equipment, I see no reason to be so attached to it emotionally that you have to shout down anyone who points out any potential flaws. I'll bet that if your post had been a glowing review they would have eaten it up!.

The only reason I can see for that mindset is that some people derive part of their identity from their camera(much like some people and their cars) and any perceived slight against it is also considered a slight against them. I guess in some ways these cameras are like any other luxury "status" good, like a Rolex or Ferrari.

At least that's my 2-bit psychoanalysis of the reason why.
 
anchoryanker said:
I saw that, I'll never understand why people get so defensive about this stuff, you'd almost think you were insulting their favorite sports team from some of the reactions. I love my DVX, but I'm also aware of it's shortcomings and can discuss the pros and cons objectively.

This is just equipment, I see no reason to be so attached to it emotionally that you have to shout down anyone who points out any potential flaws. I'll bet that if your post had been a glowing review they would have eaten it up!.

The only reason I can see for that mindset is that some people derive part of their identity from their camera(much like some people and their cars) and any perceived slight against it is also considered a slight against them. I guess in some ways these cameras are like any other luxury "status" good, like a Rolex or Ferrari.

At least that's my 2-bit psychoanalysis of the reason why.
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I agree and it's too bad that people have such extreme views about cameras, as if Camera_A is perfect, but Camera_B is total junk. Anyone who questions this goes to digital hell...

I've seen outstanding work created with the HVX-200 and I'm starting to see outstanding work created with the EX-1. Both cameras have strong points and both cameras have weak points, STILL users are able to produce great results with either camera. It's all a matter of person needs and wishes that defines which camera it best for each person.

A camera is a tool and just because someone selects a different tool from others, that does NOT make them a better or worse person than someone else.


Bob Diaz
 
RED's Rolling Shutter

RED's Rolling Shutter

Barry_Green said:
If it has a rolling shutter, it's going to exhibit rolling shutter effects -- the company may be able to minimize the effect somewhat, but it's still going to happen under certain circumstances.
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Barry do you have any idea how RED is dealing with the rolllng shutter problems? Jannard's answer was that "we use a rapid reset sensor system which is much faster than a typical CMOS rolling shutter. It is a bit slower than film so it is easier (not much) to induce skew with RED than with film. But it is MUCH better than a standard rolling shutter."

I am still learning about the rolling shutter issues but reading this link from your article I understood that one way (with trade-offs) to reduce the rolling shutter artifacts on a CMOS sensor was to use more transistors per pixel to emulate a CCD's typical global shutter so that "pixels can be integrated and read out in the same time". Seeing tests carried out by RED owners at this point seems that the shutter is still rolling, as in presumably that is not the direction RED is following.

Is it a mysterium or does anyone have any more technical details/links to share on RED's partial solution? sorry to post this on sony's thread
 
I have no info on what Red is doing about it. I do know that they're very much aware and if something can be done about it, I'd wager they'd be the guys to do it.

That said, I don't know whether they can overcome it or not; I look forward to seeing the results of Jim Arthurs' testing.

A global shutter is a possibility, but not without drawbacks; more transistors on the chip reduce the "fill factor" of the CMOS sensor, which results in losing a stop or two of sensitivity. I'd gladly give that up, but many people wouldn't, so global shutters remain rare.
 
thanks barry, some say a good ol' mechanical shutter could be another option (w/ optical VF) like on the D20. RED opted otherwise from the start partly i guess to keep the system affordable. The case is in good hands anyway
 
Red can't do anything about this flash effect. If you do a search you'll find that professional people are doing post work with Knoll light factory to fix this issue. The same can be done for the EX.
 
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From what I've heard its not difficult. There are presets flashes you make adjustments too. You don't have to create flashes from scratch. You do this right in FCP or premiere. I mean you don't have to create a flash effect for 20 minutes, just a couple of frames. Heres a demo clip of Knoll.

http://www.redgiantsoftware2.com/Downloads/knollfinal.swf

If that isn't for you maybe cameras with rolling shutter are not for you. Or don't shoot flashes.
 
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Some of Jim's RED ONE Camera rolling shutter results were finished yesterday. To my surprise, it looks like it may be about the same as the EX1.


Skew:
http://ftp.datausa.com/imageshoppe/outgoing/SHUTTER_STUDIES/RED_rolling_shutter_test.mov



Strobes:
http://ftp.datausa.com/imageshoppe/outgoing/SHUTTER_STUDIES/STROBE&ROLLING_SHUTTER.mov


Thread:
http://www.reduser.net/forum/showpost.php?p=134798&postcount=1

Jim at RED said there will be about a 10% improvement in Build 13 or 14 with a settings change.
 
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Can't download the clips from where I'm at, I'll try later today. Most interested to see the results. Did he try motion tracking?
 
I believe Jim did not, but somebody else chimed in on that thread and said it worked fine for motion tracking. Well, I guess we really would need to see this.
 
Hi all...

I haven't seen any sort of semi serious testing of the EX1... any links? A friend has access side by side to one with their RED today, but won't have the chance to do testing on this.

I really HATE this issue in general. I've done good tracks with RED footage that people have uploaded, but none of these shots have really stress tested the concept. Here's one example I did for fun with RED footage...

http://ftp.datausa.com/imageshoppe/outgoing/RED/SHAWN_CANOPY_tracked.mov

And another...

http://ftp.datausa.com/imageshoppe/outgoing/RED/GARAGE_tracked.mov

There are certain situations where you flat out CAN'T do what you can do with a global shutter... here's an example I've done with HVX....

http://ftp.datausa.com/imageshoppe/outgoing/PAN_TILT/TAKES_BLENDED.mov

and this...

http://ftp.datausa.com/imageshoppe/outgoing/PAN_TILT/NEAR_MISS.mov


...multiple takes shot without motion control and all motion tracked and blended together... a few degrees of skew will totally disrupt the end results of the tracking. Thing is... the tracking software doesn't know there's such a thing as skew, and will happily report a successful track. The problem comes when you want to do hyper-precise matching of say, four corners of a wall to a virtual set and keep them intact.

I love the RED. But you can't seperate the EX1 and the RED on these issues... they're the same. RED gives you 35mm DOF and deep color grading and the like, but CMOS they both are.

Irony is my first post the DVXUSER in a long while is the day after I sold my HVX... now I gotta buy something new...

Regards,
 
O.K.

Here's my question.

Why wouldn't this same effect be seen in fast moving objects.

I know motion blur will mask most of the effect but would it not be the case with objects such as runners, bikes, and cars moving quickly horizontally?
 
I maybe mistaken but the problem is not with fast moving objects but rather with a fast moving camera....such as a pan...that's when the wobble occurs....
 
Jim you are a great asset! Thanks for your execellent work.

If you find yourself in the Phoenix AZ area, I'm only about 50 minutes out of Phoenix (Casa Grande). Look me up and we can perform the EX1 rolling shutter tests. Man, just from the examples you've posted, I'm willing to bet the EX1 performs just about the same.

Depending on when Joel (Joelnet at reduser) gets his camera (lives in the area and I've worked with him before, due to get his camera any day now)), we might be able to arrange a direct rolling shutter comparison.
 
I haven't gotten my EX-1 yet so haven't been able to test it, but does anyone know if the half frame type exposures from at least single burst flash guns are always in the same place in the frame. That would make it much easier to fix in post.

- Lenny
 
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