Slow sensor readout speed can lead to ‘rolling shutter’ or ‘jello’ effects, which can affect both stills photography and video. But how bad is the Lumix S1R II’s readout speed, has Panasonic really dropped the ball here and will it really affect your results – or is it the Internet just going crazy with yet another thing to start yelling about?
So first, the new Lumix S1R II is a pretty remarkable camera, both for its capabilities and its price. For stills photographers it offers 44.3MP resolution, a 177MP high-res mode, 10fps continuous shooting with mechanical shutter and up to 40fps with electronic shutter.
For filmmakers, it offers 8K 30p, 6K open gate and 4K capture up to 120p. It can record Apple ProRes RAW HQ internally, offers 14-stop 1V-Log/V-Gamut and has an internal cooling fan. These are serious specifications at a very competitive price.
So how has Panasonic achieved these high-end specifications at this price point? There are probably all sorts of different factors, but one stands out – it has used a regular BSI CMOS sensor rather than the stacked sensor design in rival models.
Why is readout speed important?
Stacked sensors cost more to make but offer faster readout speeds. This is a factor both for stills photography when shooting high-speed bursts with the electronic shutter, and in video when filming subjects moving quickly across the frame or when performing ‘whip pans’ with the camera.
Almost all cameras use ‘rolling’ shutters – the current exception being the Sony A9 III, which has a ‘global shutter’. With a rolling shutter, the sensor data is read rapidly line-by-line, not simultaneously all at the same time. Imagine a very fast flatbed scanner. The longer the overall scan time, the more likely it is that fast-moving objects in the scene will have moved a significant distance between the time the scan (exposure) starts and when it is complete. This produces a characteristic ‘skewing’ or ‘slanting’ effect in both stills and video.
This creates a bit of a paradox in stills photography, where an electronic shutter might offer a maximum shutter speed of 1/16,000sec, for example, but actually have a readout speed of 1/50sec. Each ‘strip’ of pixels on the sensor gets 1/16,000sec of exposure, but the readout process takes 1/50sec to scan the sensor from top to bottom.
In video, this can show up as ‘jello’ effects from fast-moving run-and-gun style video, or shutter distortion (slanting) from very fast pans. It’s not difficult to provoke almost any mirrorless camera into showing shutter distortion if you pan it from side to side fast enough.
So the controversy with the Lumix S1R II is that it has a readout speed of around 1/50sec for stills photography, where rival cameras with stacked sensors may be much faster at around 1/125sec or even 1/200sec. This can make a big difference to shutter distortion. If you want to see how other cameras perform, check out this remarkable crowd-sourced Camera Sensor Readout Speeds project.
You’ll note that sensors do not have one single readout speed. It varies according to the context (photos vs video) and the video resolution/frame rate/crop factor. The readout speed for stills photography may be much longer than for video because the maker’s aim is maximum still image quality rather than video frame rates. You can’t just go by the figure for photos.
So how much does this matter?
This is where the online debate heats up. On one side you have videographers, often with considerable experience, complaining that if you’re getting shutter distortion you’re panning too fast and not filming properly, and that they (and others) have been filming successfully for years with cameras that have much slower readout speeds than the Lumix S1R II.
On the other side of the debate are users who feel that Panasonic should have gone much further, that a non-stacked sensor with a distinctly average readout speed is a disappointment, and that this severely hampers the S1R II’s appeal.
If you’ve been filming successfully with just about any Sony A7-series camera and never been particularly bothered by rolling shutter, then you should be fine with the Lumix S1R II, which actually has a somewhat faster sensor. On the other hand, if your filming style involves lots of fast movement – both subject movement and camera movement – then you’re probably going to be quite sensitive to rolling shutter effects and you might be better off with a more expensive camera with a stacked sensor.