The Future of the Electronic Shutter

May 9, 2016

By Greg Scoblete

Electronic shutters have usually been touted by still camera makers as a means to shoot quietly, without the noisy clang of a mechanical shutter, or as a way to get even higher frame rates during continuous shooting. Where mechanical shutters tap out at 1/8000 sec., electronic shutters can blaze away as fast as 1/32,000 sec. 

Stealth and speed aren’t the only virtues of an electronic shutter for stills. Since there are no moving parts, electronic shutters aren’t vibrating the camera every time they’re activated. Even as camera makers have gone to great lengths to dampen shutter vibration, they’ve gone to greater lengths to increase the resolution of their cameras and the sharpness of their lenses—sharpness which can be imperiled by even tiny vibrations when images are blown up and pixels are peeped. [To get a sense of just how far cameras makers will go to avoid vibration, consider that Phase One built a seismometer into their newest camera body.]

So an obvious question arises: could a mechanical shutter ever be fully replaced by an electronic one? Electronic shutters have long been used for digital video (both in still cameras and video cameras), and are standard on smartphones. Will they fully conquer digital still cameras next?

We put the question to two camera makers, Olympus and Panasonic, who use electronic shutters in most of their models. The short answer is: maybe, someday.

While electronic shutters are totally silent and super fast, the rolling electronic shutters implemented on still cameras have two huge liabilities that still need to be overcome. 

First, they can produce rolling shutter distortion. This distortion, most noticeable when shooting fast-moving subjects (or when using a camera while moving quickly), is the result of how the electronic shutter turns off pixels on the sensor to simulate the closing of the shutter. Similar to how a mechanical shutter’s second curtain will roll closed, exposing only a tiny portion of an image sensor to light at any given fraction of a second, an electronic shutter turns pixels off in a cascading line from top to bottom. That millisecond delay between when the pixels are “closed” or off at the top of the sensor vs. when they turn off at the bottom introduces the wobble of rolling shutter distortion—a warble that gets magnified for objects, notably propeller blades, that move extremely fast.

(How motion introduces image wobbling in a rolling shutter. Image: Wiki Commons)

Digital camera makers and image sensor manufacturers have gone to great lengths to boost the read out speed of CMOS sensors to alleviate rolling shutter distortion, says Darin Pepple, Senior Marketing Manager, Imaging, Panasonic. 

These improvements haven’t yet mitigated the second serious liability of electronic shutters–their inability to sync with a flash (electronic shutters on CCD sensors could be synced with a flash, but as the industry has migrated to CMOS, this ability was lost). 

To address both of these challenges, still camera makers and image sensor manufacturers are looking to the solution that has worked on video: an electronic global shutter. Rather than turning pixels off in a cascading sequence, an electronic global shutter turns them off (and back on) all at once.  Electronic global shutters are increasingly common on cinema cameras like the Blackmagic URSA, but they suffer their own liabilities. “Low light shooting (high ISO) is greatly impacted due to the space required at each pixel site for the electronics required to ‘flash’ the entire sensor at the same time,” Pepple says. That’s why you’ll enjoy less dynamic range when shooting in a global shutter and why cinema cameras often offer a choice between rolling and global electronic shutters. 

“The advent of a practical global shutter could very well bring about the end of the traditional mechanical shutter, further sliming the size of some cameras,” Pebble says. 

According to Olympus, “A mechanical shutter will become unnecessary when the read speed of image sensors is sped up and when global shutter becomes practical to use, but the timing is dependent to image sensor companies.” 

Outside of cinema cameras, CMOS sensors with global shutters are already in use in industrial applications. We know from patent filings that work on improving CMOS-based electronic global shutters is well underway. Last year,  Canon filed for a patent on a CMOS-based global shutter in the fall of last year. This year, Panasonic announced the development of its own CMOS sensor with a global shutter and wide dynamic range in tandem with Fujifilm.