What Is ‘Global Shutter’? Part II (Sony A9III)

This post is by Ron Dawson from The Online Photographer

Sony A9III frontThe new Sony A9III

So it’s not like we’ve never had global shutters before. Most CCD (charge-coupled device) sensors worked that way, and most early digital cameras had CCD sensors. Today CCDs are still widely used, but mostly for practical uses like microscopes and other medical equipment, telescopes for astronomy, scanners, bar code readers, and so forth. CMOS (complementary metal oxide semiconductor) sensors offered many advantages for cameras—they have higher dynamic range (remember the DR limitations in early digital cameras?), they’re much more energy efficient and generate less heat, and they offer size and manufacturing advantages because the readout logic could be integrated on the same chip. And they have far less blooming than CCDs. “Blooming” is when one photosite (pixel) becomes saturated and begins to spill over into the photosites around it. Canon was an early pioneer of CMOS sensors in cameras, beginning development in the 1990s. The first major pictorial camera to have a CMOS sensor was the landmark three-megapixel Canon D30 (not 30D!) of 2000.

At Photo Techniques magazine, I started a series of print sales to provide examples of techniques for readers called The Collector Print Program, and we offered several Canon D30 prints made by a guy I had just met named Michael Reichmann. CMOS sensors have undergone continuous development and improvement since then, and almost all pictorial digital cameras now use them. I’m not aware of any exceptions, although one or a few may exist. 

And there have been CMOS-sensor cameras with global shutter before: B&H Photo lists the Sony PMW-F55; Blackmagic Design Production Camera 4K, URSA 4K, and URSA Mini 4K; and the AJA CION. All of these are or were expensive video cameras: the Sony PMW-F55 CineAlta for instance has been described as a “super camcorder,” and the first announced price was $34,900.

Enter the Sony A9III

The new Sony A9III (which isn’t out yet, mind you, and might not be for a while) might not interest you personally for your immediate needs. But it’s probably going to prove to be a landmark camera. Depending of course on future implementation. The 24×36 (“full-frame”) CMOS global-shutter sensor demands a massive amount of processing power: Sony says eight times as much as the A9II, which was no slouch in that department. The highest shutter speed is a fantastical 1/80,000th of a second, and the sync speeds are said to go up to that (I still haven’t worked out what’s going on with the sync speed). The maximum frame rate is up to 120 per second, with new controls to set and access that. Rolling-shutter artifacts and banding will be completely eliminated.

As has the physical mechanical shutter: in the A9III, there isn’t one.

On the disadvantage side, base ISO is 250, which might result in a measurable diminishing of best-case DR. But note that word “measurable.” I think it would be unwise to make too much of that, at least until practical testing starts to get real-world effects sorted out. Until we know better, I would doubt it will be detectable in ordinary shooting.

The camera is a true tour-de-force, and a technical showpiece. As a product, it’s a niche camera meant for very serious sports, action, and wildlife shooters, and for a subset of professional and semi-pro videographers. As such it will pass by in the parade of products as all digital products do. However, as a demonstration of future possibilities and of Sony’s technical prowess, it’s astonishing. Therein lies its real meaning: to remind us what Sony can do, and to bring Sony full-frame mirrorless back into the conversation—if not front and center, at least shoulder-to-shoulder with the rest of the players.


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Featured Comments from:

Peter Jeffrey Croft: “Re ‘The camera is a true tour-de-force, and a technical showpiece.’ What an incredible camera, and as you say, a technical marvel. I’m reading Akio Morita’s [co-founder of Sony —Ed.] book Made in Japan at the moment (a bit late, yes) and it’s no wonder Japan is way out in front in so many ways. Sony treats its employees so well, as a family, with a great deal of respect, encouraging them in so many ways to be their best. My work was in the electronics field (TV broadcast) and I used to say it felt as if our management read the books about managerial best practice, then took an oath to deny and forget everything they read and do the opposite. I felt discouraged and disheartened at the lack of respect (when our chief engineer retired, he wasn’t replaced), and the lack of care about employees who felt un-valued (I was the union rep so I heard their tales of woe). Again and again, I had to wave goodbye to great guys who left because they felt un-valued and underpaid. We had secretaries who were paid more than techs! The company cared almost nothing for academic qualifications—not their business, they said. Training is not our business. It’s no wonder Japan raced ahead and is so advanced. This camera is just one example; there are many, many more.”

Jayanand Govindaraj: “My guess is that, for now, in practical terms, the 120 fps speed is meaningless and a marketing gimmick, as the camera uses slower CFE(A) and SD UHS II cards, so no amount of buffer can compensate for the slowness of the cards. I doubt you would get more than two seconds shooting at that speed before the buffer overflows—unless, of course, the RAW that is mentioned is a highly ‘compressed’ version, bordering on JPEG. In that case, the photographer will get an animal/bird/sportsman/whatever twitching, at best, and have 240 frames of that twitch to check out. If you are forced to cut the fps to get decent shooting time, I would guess there are many other cameras that will be better for the purpose, and at a lower cost.

“This is a technological tour-de-force which could well be the future, but I doubt whether it is the present.”


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