Rolling Shutter?

[Harry Clark]

With the new models and sensors (and new pricing) has there been any additional processing to get the read/reset time as close as possible to zero?
i.e., will we be able to use strobes for effect, or Unilux, or simply whip pan with a skinny shutter?
It's a fundamental issue that has not been addressed as of late. And since no other digital cinema camera (Arri, Dalsa, Genesis) has this issue, it really frustrates me when the issue of a flash or strobe makes us choose a different camera system.
Hopefully, the price bump of Epic addresses some of the tricky issues with Red One, and does not simply subsidize the low price of Scarlet.
Cheers,
Harry

[Dylan Macleod, CSC]

Okay...I know just enough to be dangerous, but doesn't a larger sensor mean more difficulties with respect to rolling shutter because of the longer physical distance to travel?

Imagine what that means for 617!?

[Vincent Thomas]

Harry, your question join mine in a way...

http://www.reduser.net/forum/showthread.php?t=22159

[ericyoung]

With the new models and sensors (and new pricing) has there been any additional processing to get the read/reset time as close as possible to zero?
i.e., will we be able to use strobes for effect, or Unilux, or simply whip pan with a skinny shutter?
It's a fundamental issue that has not been addressed as of late. And since no other digital cinema camera (Arri, Dalsa, Genesis) has this issue, it really frustrates me when the issue of a flash or strobe makes us choose a different camera system.
Hopefully, the price bump of Epic addresses some of the tricky issues with Red One, and does not simply subsidize the low price of Scarlet.
Cheers,
Harry

I've been thinking about the rolling shutter issue too, and don't think it will go away because I believe Red have found they need rolling shutter to enable faster framerates. Unfortunately even with much faster readout/reset rates the bottom of the frame is always going to be sampled at a different time to the top of the frame, so some skew will be inherent.

There was some discussion about how film has skew too because the shutter wipes across the film frame sort of like a rolling shutter. But I don't think it does have skew, because each part of each film frame, that doesn't currently have the shutter blade in front of it, is being exposed at the same time. Hence no jello effect with film.

However both can exhibit partial frame exposure with short duration strobes, although the film has a softer more acceptable edge to it due to the shutter blade being out of focus.

[ygo]

There's global shutter, which utilizes a fifth transistor in each pixel, but this can decrease fill-factor of the sensor. Global shutter is what they use for medical remote surgical operation.

[Jeff Kilgroe]

Jim has stated that the Mysterium-X sensor will have faster read reset times, about 40% faster or so and Monstro even better than that.

A global shutter isn't always the answer as there are times a bit of skew can be a good thing. We have to keep in mind that most formats, even analog medium like film, have skew.

Ultimately, I think the technology will evolve to a point where read reset times can be dialed by the user from zero to whatever, to induce the desired amount of skew. We could even take that farther by utilizing scanning algorithms or defining masks and photosite scanning orders to mimic various types of shutters and their associated skew effect; like the soft and angled fall-off of a mechanical mirror shutter.

[Harry Clark]

I've said this before, but I'll say it again.
It is not impossible to eliminate this artifact. It's merely expensive.
The Arri D-21 also uses a CMOS sensor, and uses the "rolling" mechanical mirror/shutter for timing, but suffers no issues with strobes or skew. Why? They have the sensor divided into quadrants, each with its own processor. Expensive to manufacture, but an unbelievably low price was not a primary driver there... now that we will all pony up more for FF35's, surely there is room to improve this issue.
Cheers,
Harry

[Stephen Webb]

Jim's already said that the objective is not to eliminate skew but to get the read/reset time of the rolling shutter fast enough that the skew matches film. I don't think a global shutter or a 0 read/reset is part of the plan.

[Harry Clark]

They can call it "the same as film" or "0" or "minimal" or whatever. Just so we can use strobes.
Just like with a film camera.
Cheers,
Harry

[Anders Holck]

.
The Arri D-21 also uses a CMOS sensor, and uses the "rolling" mechanical mirror/shutter for timing, but suffers no issues with strobes or skew. Why? They have the sensor divided into quadrants, each with its own processor.

Not really. The D-21 has a mechanical mirror shutter. it's electronic rolling shutter makes the redout/reset when the mechanical shutter blocks the imager.
Therefore the electronic shutter and the readout pattern doesnt affect the motion rendering at all.

It will have the exact same motion rendering as a 435 from which it's mirror shutter assembly originates.

[ygo]

........A global shutter isn't always the answer as there are times a bit of skew can be a good thing. We have to keep in mind that most formats, even analog medium like film, have skew.

Ultimately, I think the technology will evolve to a point where read reset times can be dialed by the user from zero to whatever, to induce the desired amount of skew. We could even take that farther by utilizing scanning algorithms or defining masks and photosite scanning orders to mimic various types of shutters and their associated skew effect; like the soft and angled fall-off of a mechanical mirror shutter.I agree that aesthetic reasons are important, but it's not up to the camera manufacturers to determine image beauties/moods. The camera manufacturers only need to give the artists (DPs/Directors) as much options as possible to create their art, not determine and constraint the artist on the availability of options. So global shutter with an option of shutter that mimic rolling blade with various degrees.

There are reasons the Japanese still uses mechanical shutter with their DSLR, one of them being optical viewfinder, and the other is light leakage to the floating diffusion, or sense node of the sensor. A mechanical shutter completely block light.

[Mitch Gross]

No, I believe asthetic choices are very much the areas that camera manufacturers must pay absolute attention. Until the Phantom HD, all of the Vision Research cameras were made with global shutters for technical reaons important to data analysis of high speed imaging. But for a far more cineatic, attractive image, the Phantom HD & Phantom 65 use a rolling shutter design. Now mind you, the read/write time of that rolling shutter is insanely fast, less than a millisecond, but there are still imaging qualities to a rolling shutter that make it attractive. Panavision understood this when they were evaluating the Phantom and they bought the cameras so I guess they liked what they saw.

Super fast read/write is one of the many facets that can make a camera really, really expensive and difficult to manufacture. Based on feedback RED has already improved the speed as much as possible via firmware in the RED One. I'm sure that Scarlett & Epic will continue the trend.

[Deanan]

No, I believe asthetic choices are very much the areas that camera manufacturers must pay absolute attention.

Absolutely agreed. Camera design is all about making the right compromises for the end goal. Technical perfection is not always the right goal which is why many lens designs considered beautiful are quite imperfect compared to on technically perfect ones that are cold and sterile.

[Harry Clark]

Anders,
I'm well aware that the D-21 has a mechanical shutter! ;)
The guys AT ARRI told me about the 4 processor architecture. They specifically said that it was designed to decrease the read/reset time to near zero.
And indeed, you can use the D-21 WITHOUT the mechanical shutter enabled, and STILL not have skew or strobe issues.
Deanan,
YGO is right.
Lens issues and camera issues are apples to oranges.
While I might agree that a certain amount of lens "defects" will yield a more pleasing image (if they happen to be the right defects; a certain amount of blooming or softness, but not so much distortion or anamorphic "mumps" for instance) there is really no excuse for introducing a NEW defect, especially when it is an undesirable one. There is nothing beautiful or pleasing about the skew issue.
It's possible to eliminate it for all practical purposes with a CMOS. Arri has done it. Here is my official request for it to be eliminated in the Epic.
Cheers,
Harry

[Deanan]

Deanan,
YGO is right.
Lens issues and camera issues are apples to oranges.
While I might agree that a certain amount of lens "defects" will yield a more pleasing image (if they happen to be the right defects; a certain amount of blooming or softness, but not so much distortion or anamorphic "mumps" for instance) there is really no excuse for introducing a NEW defect, especially when it is an undesirable one. There is nothing beautiful or pleasing about the skew issue.
It's possible to eliminate it for all practical purposes with a CMOS. Arri has done it. Here is my official request for it to be eliminated in the Epic.
Cheers,
Harry


It's not about adding defects, it's about looking at the big picture and making the right decisions overall. Global shutter means you have to trade off quality elsewhere that we don't find acceptable and the motion properties for global shutter aren't necessarily desirable either. Decreasing the shutter timing tremendously has many more positive advantages than going to a global shutter with the current technology.

The 4 readout thing Arri is talking about doesn't help them as the mechanical shutter provides the shutter skew and read/reset is in the shutter dark position anyway.

If you don't think it's about making the right compromises/decisions, you've never designed a camera before. Every decision you make affects something else in good and bad ways.

[Harry Clark]

OK. Let's just say I'd like to see skew improved more, and the use of strobes enabled.
I stopped by Abel today on some other business and ran into Mitch.
We got into a very technical (for me) discussion about the tradeoffs associated with different designs (Arri, Phantom, Red)
Without boring everyone here to death, I'll just say that I appreciate the challenges involved and I certainly see how different issues can present themselves when designing around an electronic sensor.
I trust that the Red Team will do all they can to minimize skew and enable the use of synched strobes with Epic.
You must understand that for me, a no-excuses camera is more important than a specific price point. But I have a better understanding of the technology now.
Cheers,
Harry

[Deanan]

OK. Let's just say I'd like to see skew improved more, and the use of strobes enabled.
I stopped by Abel today on some other business and ran into Mitch.
We got into a very technical (for me) discussion about the tradeoffs associated with different designs (Arri, Phantom, Red)
Without boring everyone here to death, I'll just say that I appreciate the challenges involved and I certainly see how different issues can present themselves when designing around an electronic sensor.
I trust that the Red Team will do all they can to minimize skew and enable the use of synched strobes with Epic.
You must understand that for me, a no-excuses camera is more important than a specific price point. But I have a better understanding of the technology now.
Cheers,
Harry

Skew is being improved tremendously for sure and synced strobes will not be an issue on EPIC.

[ygo]

Skew is being improved tremendously for sure and synced strobes will not be an issue on EPIC.That is exactly my point, you are improving by speeding up the readout process row by row to address the use of strobes. So what is next that the DPs and Directors request that is being hindered by its limitations? We don't know, but if there are more paint brushes to choose from, then we give the artist that much more degree of freedom. If you want to give your shots a certain mood, or many moods, then it can easily be done in the post. A camera should be as transparent as possible, it's not the camera, especially not the sensor, to determine the artist's creations.

There are technology today to implement global shutter without trading off fill factor of the sensor, especially for the price of 617, 645 and FF35. Also, there's a new fabrication process, where there's no need to have microlenses, thus the sensor plane receive light with the same numerical aperture as film.

617, 645, and FF35 have over a year to work out the spec', might as well use this time to properly utilize the available CMOS processing technologies.

[Jannard]

The ultimate point for us is that limitations are being lifted with each generation of electronic sensor. By isolating the sensor, and its closely associated companion electronics package, into a single, upgradeable box... moving forward becomes much less painful. A new box... not a new camera model.

Jim

[David Birdy]

Bravo,

I love seeing Red Digital Cinema move forward and continue to make smart
decisions and expand the product line...any Red Ray news Jim??


Thanks for placing the bar high Jim!
Dave

[Mitch Gross]

Eliminating skew issues and strobe-sync issues does not necessarily mean going to a global shutter. A rolling shutter can be used and the Phantom does it today. RED can do it as well and likely will in EPIC.

Skew is s result of slow write/read speed across the sensor. Speed up the process and with each frame you have a tiny bit of time as the lines begin charging, a whole lotta time as every photosite accepts light all together, and then a tiny bit of time again as the lines all discharge out.

Strobe sync is easy as well. just need to sync signals: one to state when each frame starts the charging cycle (this is important for absolute sync on such systems as motion control and 3D) and another to note the exposure duration in pulse form (industry standard is a 5 millivolt pulse IIRC). The sync pulse can be set to trigger dead in the middle of that long time the whole frame is getting exposure, and there would never be a sync issue again with strobe lights. And if the read/write cycles were quick enough then there would be no problem with skew or other motion-related issues, such as harmonic vibrations in car and helicopter shots. This is especially important in composite shots, like just about ever car commercial made these days (well, before the economy imploded).

[Yean Loon]

The ultimate point for us is that limitations are being lifted with each generation of electronic sensor. By isolating the sensor, and its closely associated companion electronics package, into a single, upgradeable box... moving forward becomes much less painful. A new box... not a new camera model.

Jim

I think that's the most concise and logical answer. Really explains everything.

cheers,

yean

[ericyoung]

...Strobe sync is easy as well. just need to sync signals: one to state when each frame starts the charging cycle (this is important for absolute sync on such systems as motion control and 3D) and another to note the exposure duration in pulse form (industry standard is a 5 millivolt pulse IIRC). The sync pulse can be set to trigger dead in the middle of that long time the whole frame is getting exposure, and there would never be a sync issue again with strobe lights...

Unfortunately that doesn't solve the problem with non-syncable strobes such as emergency service vehicle strobes or paparazzi flashfests.

[Mitch Gross]

Unfortunately that doesn't solve the problem with non-syncable strobes such as emergency service vehicle strobes or paparazzi flashfests.

And neither will a global shutter as you may get the exposure or may not.

But if you're clever and enterprising, then those strobes can be slaved as well. It's easy on a paparazzi flash, as you can feed a cable to a sync input port on any detachable camera strobe. Easy to rig. And I've seen on vehicle strobes rewired for this slaving use as well. Just depends on your budget really.

In the end there is absolutely no way to always get everything, even in film or on a global shutter. The sensor must refresh, even if only for a millisecond. The old adage in film when shooting guns was that if you saw the muzzle flash in the viewfinder then you didn't get it on film. Same problems no matter what the media.

[tj williams]

Since the new big brains are for STILL photos use also we must presume that there will be no artifacts in flash photography? Otherwise Nikon n Canon would win.

[Jannard]

Since the new big brains are for STILL photos use also we must presume that there will be no artifacts in flash photography? Otherwise Nikon n Canon would win.

Why would we want to do this and have Canon or Nikon win?

Jim