We hear the term "global" and "rolling" shutter a lot. But how do these two types of shutter differ, and what does it mean for your footage? Sign up for our free e-newsletter here www.videomaker.com/yt-shutter
Thank you for the great video. I'm an Australian Vocational College teacher from Melbourne, with an Electrical Engineering background, and I'm an amateur videographer. You have done an excellent job of explaining the essential differences between the rolling shutter and the global shutter. For those folks who may be interested the nerdy technical details are: *A camera with global shutter has a very fast pixel clock, and the read out term in this video, refers to each pixel from each row being read or turned on, one at a time and the color data is converted from an analog to a digital value by an electronic device called an Analog to Digital Converter or ADC; *As soon as the ADC finishes converting the data into digital form (12 or 10 bits for professional to prosumer video equipment, 8 bits for consumer video cameras), the digitized data is sent over a data bus to the video processing engine. This engine is very similar to your smart 'phone or computer; it has memory, a CPU (Central Processing Unit) and a mass storage device, whose job is to perform various tasks, such as video color correction, noise removal, converting the RAW footage into a codec such as AVCHD or MP4, and then write the AVCHD data to a microSD card or for RAW data directly to an SSDD; *The faster the read out rate for each pixel that is turned on to have its data read and converted, requires a correspondingly faster sensor with associated faster read out electronics and image processing data; it's both how fast the image sensor can send out the data to the data bus and how fast the video processing engine can work, that influences if the camera features a global shutter or a rolling shutter. The comparably fast professional cameras, such as the Sony Cine Alta, Arri Alexa, and Red One, to name a few, have the highest technologically achievable image sensors and video processing engines, at the time of their manufacture. Also due to the much higher data rates (measured in Mbps), microSD or even Compact Flash cards aren't fast enough to keep up with storing these faster rates. This is why professional grade cameras use RAW recorders with high data rate SSDDs, requiring the use of external recorders, such as Odyssey 7Q. CMOS sensors are cheaper to manufacture and because they share the same basic fabrication technologies as electronic memory systems, and are easier to integrate into on-chip processing devices. This flexibility comes at a price, with CMOS pixels having higher noise, requiring they stay on for a longer period of time, compared with CCD sensors. The requirement to keep a CMOS pixel on for longer, also limits the read out rate for a camera using a CMOS sensor. The higher inherent noise of CMOS sensors, also explains why their low light performance is still not as good compared with CCD image sensors, at higher ISO settings. CCD image sensors require additional fabrication steps, and this is why they are comparatively more expensive. With a CCD image sensor able to operate at higher pixel clock read out rates, it's possible to have very high Mbps figures, high color space numbers such as 4:4:4, although such cameras are quite high in cost and the camera bodies need to be either made of magnesium or aluminum, or need to be built into larger bodies; higher pixel and video processing engine clock rates dissipates a greater deal of heat. CCD cameras can achieve fantastic frame rates, such as 10,000 fps at a premium price. In electronics there's an old rule of thumb - the faster the component or the more energy the component needs to handle, the more expensive it is. This is also why even the comparatively cheaper to manufacture CMOS sensors can be higher in price if you purchase a camera with the lowest possible wobble; its CMOS sensor has a higher clock rate than the cheaper brands or models. Research and Development is ongoing, and CMOS manufacturers introduce incremental improvements, and after many decades of research they produce something like the Sony NEX-FS700, which has the lowest amount of wobble compared with a cheaper camera, unless a competitor has released a camera with a new generation CMOS sensor with higher pixel clock rates and higher video processing engine clock rates, at the same or lower price point. P.S. I wanted to add that I'm not sure how the data read-out is done on the image sensors, regardless if they are fabricated using CCD or CMOS technologies. I haven't been able to find any further information, so I presume such pixel data read-out methods are closely guarded trade secrets. In theory, at least, one method to implement data pixel read-outs for rolling shutters, to keep costs down, may be to use one ADC (Analog to Digital Converter) and each pixel has its Red, Green and Blue color sensors read out separately one at a time, one video line at a time (every pixel or picture element has three color sensors). For a 2k (1920 x 1080p) video resolution, 1,080 video lines are read out each one at a time, with each line requiring 3*1,920 = 5,760 separate read outs for Red, Green and Blue photo sensors. Also in theory at least, for global shutters, each line may have its own ADC requiring 1,080 ADCs for a 2k resolution image sensor, reading each line simultaneously. This would require a larger image sensor if the ADCs are on the image sensor integrated circuit themselves. The ADC binary data may be sent over several memory channels or much higher data rate memory buses, for data capture and CPU processing to the video image buffer. The video image buffer then sends the video image data out with the audio data to be recorded on an SSDD card. Higher global shutter video data rates require faster ADCs, CPUs and memory clocks requiring a bit more power to run. This may explain why global shutter cameras are more expensive. To compare power consumption (based on data from their operating manuals) the Sony NEX FS700 rolling shutter camera consumes up to 22 Watts, whilst the PMW F55 consumes up to 25W. When first released back in 2012, the FS700 cost USD8,000 (body only) and the F55 cost USD34,900 (body only). There was also a Sony PMW F5 model released in 2012, but that was a rolling shutter camera upgradeable to the F55. The body only price for the F5 was USD19,400. www.dpreview.com/articles/6772362590/sony-4k-ready-nex-fs700-fs700e-camcorder nofilmschool.com/2012/11/sony-official-price-f5-f55-digital-cinema-camera-cost For shooting scenes where fast motion is not required (such as people walking around), a prosumer to professional rolling shutter camera will do a very good job, and there's no real benefit to using a global shutter camera. However, when shooting fast action scenes, particularly where the camera is panning very quickly to follow a running talent/subject or shooting out the side of a moving vehicle a global shutter camera is IMHO a must for professional film making.
Neil thanks for taking the time to explain this. I am confused about something though. I've read that the new Sony A9 has an electronic shutter speed of about 1/150s but at the same time allows an exposure of 1/32000s. How do you reconcile these two figures? Wouldn't a 1/32000s speed only expose a tiny amount of the sensor at its very top? thx.
Thanks for the great video. Watching a TV show recently with a friend, a helicopter's blades started turning and when they moved they were skewed and looked curved. I pointed this out and told him what it was but all I could explain was "technical stuff" in the camera made it happen. Now I can give a better explanation and sound like I actually know what I'm talking about :)
Another great lesson! Thanks for posting! I have AX100 - amazing 4K camera, but not very good to show motion. Many people blame this on the lack of 60p, but I think it is because of the rolling shutter that can distort badly the objects in motion. The question in my mind is: the recommended shutter speed for 30p video is 1/60s, but won't it be better to allow in such cases much higher speeds that would reduce the distortion, even though the movement might become choppy?
This is an excellent explanation. Thank you so much for your time and energy explaining this confusing subject to me. I really learn through videos like this and not through books.
A good demonstration of the basic principle. The bit that confused me initially was why they read slowly and the part that really messed with my head was why it doesn't happen when the physical shutter is used. For example: many modern cameras with bad rolling shutter scan at around 1/15th (sony A7III, EOS R, Nikon Z7) but with a physical shutter of 1/15th you don't get the same slewed image 🤯
Ah, I see. So basically the speed of the image processing helps eliminate this too, not just the other things you mentioned. Good to know about the shutter. Thank you!
Thanks Greg, Great video. You answered my question immediately. Just seeing all of these forums about the new Sony A7sIII and they're wanting global shutter. Hopefully it is released soon and people can stop speculating. BTW - the props were on point. lol
Great video - 8 years old and still perfect! Thanks for the effort! I am especially grateful for the analog rotating shutter explanation. Why do basically 99% percent off digital sensors today only use the rolling shutter readou? Are there downsides of global shutter readouts?
Thanks. That was one of the best explanations of something I've had a hard time understanding. I would like to see some slow-motion examples (maybe side-by-side examples) of various subjects in motion using both kinds of shutters.
+Rochdi Tidjani Thank you for your comment, We're glad it helped you. For the record though... We worked hard on those props... Thanks for watching. :)
Does the shutter type help with limiting the blooming/white-out effect of moving from lower light to bright light conditions? And thanks for the great description about shutter types.
IDStudio7 When you increase the shutter speed, the shutter doesn't actually get faster, the gap just becomes smaller, so increasing the shutter speed doesn't remove the rolling shutter effect
Even though old school film cameras had a rotating shutter (not rolling), the frame of film never moved for 1/24th of a second. Professional cameras were crystal controlled to shoot at 24 FPS, a foot and a half of film per second or 90 feet of film per minute. A thousand foot magazine runs just over 11 minutes.
Really clear explanation thanks, I kinda get it now. I suppose that the way of combating the 'jello' effect is for the camera manufacturer to have very fast readout times as you stated. I wonder what will happen when the new 'organic' type sensors will come out-will video look worse or better?
How does the rolling shutter in still mode bring the shutter surface back around to the top (I saw a slo-mo video that didn't even show it going back up, and I'll see if he knows the answer too)?
Fuji X-T1 has electronic and mechanical shutter. It seems the electronic shutter will operate in rolling mode as explained here since there are issues with fast moving objects with this camera when using the electronic shutter. These issues don't exist when using the mechanical shutter. Does that mean that when mechanical shutter is used the sensor works in global shutter mode?
There was also a technical paper published by IEEE (Institution of Electrical and Electronics Engineers), proposing using additional image processing to correct for the rolling shutter effect. URL: mpac.ee.ntu.edu.tw/~chiakai/papers/liang_tip08.pdf
it takes less processing. Less work also helps with cooling. Media doesn't need to have as fast of a write speed if its being fed the data in smaller chunks.
***** Wondering if one shouldn't prefer global shutter over image quality (e.g. 4K) in generall. That is, get a used Canon 5D Mark II for a somewhat higher price than say the Lx100. What good is resolution if what is captured has weird look?
Yes. If the camera has a CMOS sensor it has a rolling shutter. If it has a CCD sensor (mostly older cameras/camcorders) hen it has a global shutter. Your GH3 has a rolling shutter.
