If you own a recent camera, particularly a mirrorless camera, one of the features you likely have access to is a choice of shutter modes.
In the good old days, the shutter, which is the mechanism in your camera that lets the light in your scene into the camera and onto the film plane or the sensor plane, was mechanical. Originally, it was something as simple as a rotating wheel with a hole cut into it. Mechanical means moving parts.
Shutters until recently were still all mechanical. But we recently were treated to the first professional camera with no mechanical shutter at all. In fact, today, you may not have any mechanical parts in your camera body at all. We’ve come a long way.
So if not mechanical, what? Electronic. Of course. Just as everything else in the world has moved from analogue/mechanical to electronic, so to have the mechanisms that control cameras. Virtually all controls in mid-to-higher-range mirrorless camera bodies are electronic. But the technology is not perfect and so most cameras also still include a mechanical shutter and give you the choice of selecting one or the other, or even a combination of both.
My latest camera, the Canon EOS R5 includes both. I’ve never tried the electronic shutter. Thought it was about time that I did. But first, in my usual geeky fashion, I had to learn when and why to use it. Here’s what I found out.
First let’s define what an electronic shutter is.
Mechanical shutters, as noted, operate by placing something opaque in front of the sensor and opening and closing it (or moving it) quickly, based on a preset time selected in the shutter settings. Mechanical shutter speeds can range from almost infinite in bulb mode to typically 1/8,000 second at its fastest. Think of what that means – something moves in front of the sensor so quickly that it creates an opening for light to pass through to the sensor but the opening is there for only 1/8,000 of a second. That’s amazing to me. No wonder mechanical shutters have a designated lifespan – usually around 500,000 actuations in higher end cameras.
Electronic shutters operate completely differently. Nothing sits in front of the sensor. Instead, the individual pixels in the sensor itself turn on and turn off at the designated speed. This permits a theoretical shutter speed of up to 1/32,000 of a second! Holy moly! I mentioned that the technology was not perfect though. At the moment, we can’t turn on, then turn off, all the pixels in the sensor at the same time. Instead, one horizontal line of pixels turns on, then the next line turns on, then the next and so on. Similarly, they then turn off, line by line. If you have ever watched an old TV, you will see flickering – it’s the same premise. On old TV’s, they could only display one horizontal line at a time, followed by the next and the next. In both electronic shutter and TV, the “readout” as it is called is usually too fast for the human eye to see, but in some older TVs, you can.
This technology has improved exponentially over the years, to the point where the readout is almost instant across the full sensor. Once we reach the point where the full sensor is activated or deactivated at the same time, the electronic shutter is then called a global shutter. Why is this important to know? Stay tuned.
One other feature of mechanical and electronic shutters is the noise they make (or don’t make). We are all familiar with the clacking of a mechanical shutter. We both hear it and feel it. For me, it’s reassuring, confirming that I have indeed exposed the image. Mechanical shutters can vary in volume, with some being really really loud and piercing (like the brand new Canon EOS R7), while others, like my Canon EOS R5, have a muted, soft sound that is very appealing. Depending on the shooting situation, and personal preferences, you may or may not want a physical sound. I prefer one.
Electronic shutters make no native sound. They are eerily silent. You can press and hold the shutter and have no physical confirmation that any images have been taken, except for the image count changing in your viewfinder or on your LCD. Some manufacturers now include an electronic shutter sound setting in their menus, so that folks like me can still have a reassuring sound. Best of all, the volume is adjustable.
More important, you don’t feel an electronic shutter fire. Since mechanical shutters are mechanical, it is possible to introduce a very small shake to the camera as the shutter fires. Today’s modern IBIS (in-body image stabilization) compensates very well for this, but still, if you want a pure shooting experience with no sound and no shake, electronic seems to be the way to go.
The other big advantage to electronic shutter is continuous firing rate. With most cameras that offer both, continuous firing rates can be up to double what they are with mechanical shutters. Instead of 15 frames per second, you can get 30. This big advantage is offset though by in-camera buffers that fill up that much more quickly and the need to review and process that many more images after the fact. But to get the perfect shot of that bird grabbing the fish from the river, it might be worth it.
One other advantage of electronic shutters is no image diffraction at the edges, at least not resulting from the edges of the shutter interfering with light paths to the sensor. There can still be diffraction from lens optics though.
So why not shoot electronic all the time? There are some disadvantages, one of which is something called “rolling shutter”. The very reason you shoot high speed continuous electronic is typically to capture every detail of a high speed action scene moving in front of you. But because the electronic shutter fires one sensor line of pixels at a time, it is possible for the action to move slightly between the top and bottom of the firing sequence for that one image. If the action is fast enough, the image can look stretched, bent, bowed or skewed (in stills) or wobbly and jello-like (in video) with electronic shutter. So you’ll need to practice with your camera to see under what motion conditions this distortion occurs with electronic shutter. In other words, there is an upper motion limit in your scene when using electronic shutter. This distortion doesn’t happen with mechanical, but you get fewer frames per second. And when the day comes when we have cameras with global shutters, this issue will no longer exist.
Another prime disadvantage occurs when using flash. With some cameras, you simply cannot use electronic shutter with flash photography. It’s only in the last few months that cameras have emerged that offer flash options. The reason is simple: just as physical movement can interfere with electronic shutters that read sensors line by line, the very short burst of light of a flash brightens and fades over the course of the same line by line readout. Parts of the scene will be dark and parts will be bright, resulting in uneven light or banding across the image.
And just to complicate things further, some cameras offer electronic, mechanical and a combination of both shutters. This third option is often labelled “Electronic First Curtain”. It is designed specifically to address camera shake in low shutter speed situations or where the shutter speed is not optimized for the focal length of the lens. Personally I like hybrid solutions that take the best advantage of available features that may exist for other reasons. And without getting too technical, it is also a very efficient exposure solution.
In some cameras, the ability to select one mode or the other is directly tied to the desired shutter speed, with one or more of the options not available with slower shutter speeds and available with higher shutter speeds.
So the bottom line is this: electronic shutter does provide some distinct advantages in very specific situations. Wedding and event photographers love it, pressroom photographers love it, sports, bird and wildlife photographers do too (mostly). Many of us who often shoot with slower shutter speeds also love that hybrid solution. For the rest of us, it provides an option to consider to save mechanical wear and tear.
So if your camera is equipped with both mechanical and electronic shutters, give electronic a try and learn how each can work to your advantage.
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