> Global shutter is a method of ending an exposure where all the image data is captured simultaneously. This is distinct from most existing shutter systems (electronic and mechanical) that start and end progressively: working their way across the sensor.
Buried at the bottom of the article. This is interesting for especially video and sports photography. Some cameras with slower sensors suffer from the rolling shutter effect where fast moving subjects get distorted because the subject or the camera is moving. Think e.g. lampposts looking diagonal when shot from a fast moving car. Capturing all the pixels in one go solves that.
Cropping the sensor is a common way to counter rolling shutter with current cameras. Basically, that means you are not using all of the pixels on the sensor and capture a smaller area. Aside from the quality, this also means that you don't use everything the lens captured; it's cropped away. So, it looks like you are using a larger focal length than you actually are and you can't capture at the full width of the lens.
Lots of cameras use cropping to support higher resolutions and frame rates because they can't read out the sensor fast enough. This new sensor can use the full resolution and doesn't have to crop.
And like with photography, you use shutter speed and aperture to control what the video looks like. 1/30th of a second is actually a relatively long exposure for a photo. And that's also potentially a lot of rolling shutter to deal with. An instant and fast readout means you have more wiggle room to play with this creatively or shoot in very bright or low light.
Most higher end cameras like the Panasonic G6, Nikon Z8/Z9, etc. hardly have any rolling shutter. You'll certainly NEVER see rolling shutter in any PRACTICAL application for video unless you pan like a true madman, either in photo or in video. (I am a professional photographer and videographer....)
In fact for sports and wildlife, you'll NEVER see rolling shutter in pretty much any existing camera, either in photo or video. For photography it's been like this for decades and for videography recently.
Where rolling shutter does appear is in the use of the electronic shutter only, but the Nikon Z9 already solved that, same with the Sony a1.
The main benefit is flash sync and a very SLIGHT improvement in some types of distortion when shooting at very high shutter speeds. I'd argue that the Nikon Z9 is a much better camera if not wanting flash sync due to its lower base ISO.
So to reiterate, the main benefit is not the reduction of rolling shutter, especially since any camera in this price point already has minimal rolling shutter.
Global shutters are COOL, and the reduction of rolling shutter is COOL, but not the main point, though of course most future cameras will probably switch to global shutters at some point if the base ISO can be lowered.
>You'll certainly NEVER see rolling shutter in any PRACTICAL application for video unless you pan like a true madman
Fast lateral movement doesn't just happen on a whip pan. Any scene involving fast vehicles, high speed machinery or strong vibration is likely to have some level of rolling shutter artifacts. Many perfectly normal tracking shots will have some artifacts, particularly if you're shooting handheld. Modern fast-readout sensors are very good, but they aren't perfect; to a great extent, we've just got used to seeing mild rolling shutter artifacts and don't immediately recognise them as an image quality defect.
There are still lots of good reasons to use rolling readout sensors, but there are also many real advantages to global sensors.
It’s not a “very SLIGHT improvement” as you write. It’s VERY SIGNIFICANT. Even the Nikon Z9 has roughly 4ms rolling shutter speed. Light travels faster than you imply here. A lot faster.
It's not the speed of light that matters. It's the speed of objects in the field of view (or, more specifically, the speed of their image on the sensor compared to the speed of the shutter across the sensor).
Also worth noting that, unlike physical objects, images are not bound by the speed of light. Patterns of light and shadow can move across a sensor at unrestricted speeds.
I'm confused what this means. Are patterns of light and shadow not also light, and bound by the speed of light (on the upper end)? How can patterns consisting of light (or the absence of it) move faster than light?
In other words, speed of a projection of light from 3d space to 2d space may be higher than the original speed in 3d. (Because one dimension gets squished to 0, so movement in this dimension is perceived to be instant.)
It's like a diagonal of a cube 1x1x1 has length sqrt(3), but if you apply orthogonal projection onto R^2, its image will be a diagonal of a square and it will have length sqrt(2). Shorter distance -> shorter time to travel.
> It's like a diagonal of a cube 1x1x1 has length sqrt(3), but if you apply orthogonal projection onto R^2, its image will be a diagonal of a square and it will have length sqrt(2). Shorter distance -> shorter time to travel.
This example doesn't make sense to me. In that analogy, wouldn't anything on that diagonal appear to move more slowly in 2D than the same thing moving along the diagonal of a face? The cube diagonal would make it move farther than it does in 2D space.
I remember seeing a simulator in my optics class that combined multiple wavelengths of light. The interference pattern moved faster than the speed of light, but that was fine because information wasn't moving faster. That was just the result of adding them together.
But when you move the laser emitter in your hand you're controlling the speed in that 2d space, not in 3d. You don't ever affect the position of photons in the Z dimension. So you’re not constrained by speed in 3d which would later be slowed down after being projected. So you move your laser emitter along the diagonal of a face with velocity v. And the perceived light which would get projected onto a plane needs to match the position of the emitter on the face. Which creates the illusion that light travelled along the 3d longer diagonal faster than at v (in order to match the projection which describes how you/camera sensor see the light). But in reality the light never travelled along this longer diagonal. It’s only an illusion. And it is this illusion that we’re measuring the speed of. Photons on this diagonal arrived straight from the emitter, i.e. each of them appeared in only one point of the diagonal throughout its entire history. In other words, the photon at the beginning of the perceived movement is a different photon than at the end. They travelled along different paths. And when some photons were at the diagonal, some others were on their way there.
Shine a laser into space and the image of your laser can be much faster than the speed of light. Nothing actually moved faster than the speed of light though.
Stand a meter away from a wall and wave a laser pointer such that the spot travels back and forth between two points a meter apart in one second. Move two meters away, but keep your movement exactly the same; the spot now moves two meters in one second.
Move two light-seconds away and do the same movement. The spot now moves two light-seconds in one second: twice the speed of light. Of course it takes two seconds from when you turn the laser on to when an observer at the wall would see it, and four seconds before you see the spot on the wall, but the spot itself moves faster than light.
Ah, so for the sake of capturing conceptual / perceived "objects", the global shutter, at least, can do a better job at what would be perceived during a short period of time that the shutter opens and captures each pixel.
A rolling shutter might capture points along the way but leave gaps in comparison. In the laser pointer example, you'd probably want a longer exposure, but the global shutter would still give you uniform capture better matching what your eyes / brain perceived.
What are you trying to argue? I am simply stating that speed of light is faster than rolling shutter speed. You’re trying to make a point about some edge case scenario that doesn’t apply to 99.999999% of use case for photography and videography.
For video you typically set shutter speed to half a frame. The most common frame rate is 24FPS, so you get 1/50 shutter speed. It’s lousy for a photo, but good for video , since you want motion blur, so that the video isn’t janky. You control light through ND filters and LED/tungsten lights, not through shutter speed, since shutter speed affects motion blur and you want to make that choice independently of exposure.
120FPS is good for sports or wildlife, but those are special. For normal stuff, 24FPS is good. And even with wildlife, you’re probably not recording at 120FPS all the time, only during quick action. Otherwise you’re just wasting space on your memory card with identical frames. Battery as well.
> I'd argue that the Nikon Z9 is a much better camera if not wanting flash sync due to its lower base ISO.
Yeah. I think a lot of people focus too much on those "high end" specs and too little about small, practical, quality of life things.
I remember how I instantly liked Fuji X100 for its built in ND filter. Yes, you can screw a filter on by yourself. Then you suddenly find yourself on a sunny beach and you wish you had your photo bag with you.
Not saying global shutter isn't nice feature, but that 250 base ISO can be a bit of a hassle depending on what kind of photography you do just like not everybody is going to benefit from the new shutter.
The faster available shutter speeds will compensate for the faster base ISO except where the superior dynamic range of a lower ISO is needed or when a longer shutter speed is simultaneously desired.
They're pretty essential for any situation where you can't just stop down the exposure in the camera. If you want a long exposure shot of some crashing waves on a bright day for instance, you might not be able to just increase the shutter speed or narrow the aperture without ruining the intended photo.
I personally like to make dreamy photos wide open with relatively long shutter to accentuate movement. Some of it in full sunlight. Yes, ND filter is essential then.
Global shutter is essential for serious drone photography or photography from platforms with undamped vibrations like machinery. It means you will have discontinuities in features of the picture. You will need to re-stich the photo or post process it. For video it is just bad. An example of such pixel perfect uses was we were able to know the size of a marking on the ground with centimetre accuracy by counting the pixels.
Modern gimbals are amazing and do away with much of the issue but if you are needing pixel accurate features global shutter is the way to go.
Not just the global shutter, but 120 FPS with full AF and AE is huge too. The A9III is going to be the best sports camera out there for a few years I think. Of course, you're going to pay through the nose if you want access to that tech.
I can't wait for them to gain back the dynamic range and for it to roll down to less expensive cameras in the future.
> Some cameras with slower sensors suffer from the rolling shutter effect where fast moving subjects get distorted because the subject or the camera is moving. Think e.g. lampposts looking diagonal when shot from a fast moving car.
These days this is the least of your worries with a camera with rolling shutter. I got a Nikon Z-fc, knowing from the reviews that it would have a rolling shutter, because I don't mind these types of distortions.
What the reviews didn't mention is that many LED based lights actually alternate red, green and blue LEDs in quick succession. And you see that in photos as horizontal streaks of rapid changes in white balance. This also happens with projectors that are LED based, and CFTs if their drivers aren't fast enough.
Are you sure that's an artifact of the light source emitting colors sequentially, and not an artifact of the camera sensor detecting colors sequentially?
> 1/30th of a second is actually a relatively long exposure for a photo.
As an aside, in video & motion picture cameras the frame rate isn’t the exposure length. You need to account for the time the shutter is closed. So the real exposure is about 1/60, still slow but much more manageable.
> Cropping the sensor is a common way to counter rolling shutter with current camera
Not in my experience. For full-frame 35mm digital cameras, the most common way to counter electronic rolling shutter effects is, ironically, a very fast mechanical shutter.
In digital cameras with mechanical shutters, which include all Canon/Nikon/Sony/etc. consumer DSLRs and mirrorless cameras, the electronic shutter programmed to stay open for much longer than the mechanical shutter, which allows there to be a time instant when all pixels are simultaneously electronically open. The mechnical shutter then opens and closes during that time.
The rolling shutter on a Sony a7 is about 26ms. Mechanical shutters can beat that easily, and can be as fast as <0.2ms.
(Electronic shutters can be faster on a per-line basis. But they will still take 26ms to roll through the image for a rolling shutter sensor. So if your electronic shutter is set to 0.01ms you'll still be seeing 0.01ms exposures at each line but it will take 26ms to roll through the image.)
I don't think you're right about mechanical shutters being faster. The type of mechanical shutter on most cameras like this is a focal plane shutter[0]. It has two curtains - an upper one and a lower one. When the shutter is closed, the two overlap. For a long exposure (typically anything longer than 1/100s although some cameras are faster) the lower curtain will fall all the way, then the upper curtain will fall to close it off again. But at faster shutter speeds, the upper curtain will start falling before the lower curtain has reached the bottom, and so you can get exactly the same rolling shutter effect with a mechanical shutter as with an electronic shutter. For very fast shutter speeds, the exposure is a narrow slit between the two curtains that travels down the image at a much slower speed than the exposure time, and this is why most cameras can't synchronise with a flash at speeds faster than 1/100s or so. So therefore the type of mechanical shutter in most DSLRs and mirrorless cameras effectively have a rolling shutter transition time of 4-10ms, which is much more than the 0.2ms you claim.
Video-specific cameras are where this might be improved, because you can have a shutter which is a rotating disc, and this can allow faster opening/closing times, because it doesn't need to speed up from a standstill for each frame.
There exist central shutters which are mechanical shutters that act as a global shutter, but these are unusual because they need to be built into each lens you attach to the camera. These are typically limited to a maximum speed of 1/500s.
Buried at the bottom of the article. This is interesting for especially video and sports photography. Some cameras with slower sensors suffer from the rolling shutter effect where fast moving subjects get distorted because the subject or the camera is moving. Think e.g. lampposts looking diagonal when shot from a fast moving car. Capturing all the pixels in one go solves that.
Cropping the sensor is a common way to counter rolling shutter with current cameras. Basically, that means you are not using all of the pixels on the sensor and capture a smaller area. Aside from the quality, this also means that you don't use everything the lens captured; it's cropped away. So, it looks like you are using a larger focal length than you actually are and you can't capture at the full width of the lens.
Lots of cameras use cropping to support higher resolutions and frame rates because they can't read out the sensor fast enough. This new sensor can use the full resolution and doesn't have to crop.
And like with photography, you use shutter speed and aperture to control what the video looks like. 1/30th of a second is actually a relatively long exposure for a photo. And that's also potentially a lot of rolling shutter to deal with. An instant and fast readout means you have more wiggle room to play with this creatively or shoot in very bright or low light.