GH3 electronic shutter

One of the interesting new features of the Panasonic GH3 (my review) is the possibility to use an electronic shutter. It's not correct to say that this is a new feature, though, as the Panasonic G5, launched some months earlier, also has an electronic shutter. Probably, these cameras share some sensor components.

The electronic shutter has the advantage of being silent, of course, since no mechanical shutter is moving at all. It probably also has a quicker response time, however, I have not tested if this is actually a fact.

On the downside, the electronic shutter suffers from heavy rolling shutter artefacts, making it virtually unusable with moving subjects, or with a long lens. It also does not work with a flash, and cannot be used with high ISO or a very slow shutter speed. I'll get back to all of this in the article.

Silent operation

As said initially, the electronic shutter is interesting because it is totally silent. Normally, when making an exposure with the mechanical shutter, what happens when you press the shutter is this:

1. The camera focuses (unless you have selected manual focus, MF)
2. The camera stops down the aperture, unless you have set the largest aperture
3. The mechanical shutter closes, and the sensor is made ready for an exposure
4. The mechanical shutter opens for the exposure
5. After the exposure is finished, the mechanical shutter closes
6. The mechanical shutter opens again for continued live view
7. The aperture opens up again

The focusing creates some noise. However, with most lenses, this is pretty much negligible. I have measured the focus noise for various lenses here, and it appears that only the Lumix G 20mm f/1.7 pancake lens has excessive focus noise.

Also, changing the aperture makes some noise. This is, by the way, why some users have reported the clicking noise when using the premium Lumix-Leica 25mm f/1.4 lens. I have measured the noise when changing aperture on various lenses, and they are mostly quite comparable.

Finally, what makes the most noise, is the mechanical shutter. Probably because it travels very fast. With the electronic shutter mode, you avoid this noise. Since it is so dominating, most people probably don't notice the noise of the aperture change, anyway.

When using the electronic shutter mode, the camera skips steps 3-6 in the above list.

For the ultimate in silent operation, I took this image, out of a series of exposures, using the Lumix X 12-35mm lens at 12mm f/2.8. When using the maximum aperture, the lens does not change the aperture before the exposure, and there is no noise whatsoever, beyond the initial autofocus sounds. In retrospect, I could have stopped down the lens some, as I notice that the foreground is a bit out of focus. Probably, the crowd would not have noticed anything anyway:

Also, when not using the mechanical shutter, there is less vibrations, which is good for the stability.

Limitations

The electronic shutter cannot be used with a flash. Not the built in flash, nor an external flash. Not even with the external flash in non-TTL auto mode, or in manual mode.

You cannot use the mode with exposures longer than 1s, or with an ISO higher than 1600.

Due to the latter limitations, one could speculate that the image quality is worse for the electronic shutter. To test this, I took the same picture using both shutter types, both images at ISO 1600 and 1s exposure:

Mechanical shutter	Electronic shutter

And here are 100% crops from both images:

As far as I can tell, the images are identical. So there appears to be no reason to worry about the image quality when using the electronic shutter.

Rolling shutter artefacts

So, the silent and vibrationless operation is the advantage of the electronic shutter. What about the disadvantages?

I have examined the rolling shutter effects of the GH3 video, compared with the GH2, and found that the GH3 has less artifacts during video recording. On the other hand, I also saw that the electronic shutter mode of the GH3 produces very pronounced rolling shutter effects.

The rolling shutter artefacts of GH3 video is largely "academic". You only see it when you deliberately try to provoke it, e.g., by excessive horizontal panning during video recording. For normal use, this is not much of a problem.

The electronic shutter rolling effects are a problem with real life use, though. Here is a pair of example images taken using both shutter types, at f=32mm, f/2.8, 1/320s, ISO 800:

Mechanical shutter	Electronic shutter

Setting a faster shutter speed would not help. You would still get the skewed car using the electronic shutter. This is because the speed of the sequential sensor readout is independent of the shutter speed.

Moving subjects is not the only problem with the electronic shutter. Camera shake can also be a big problem. Even if you use a very fast shutter speed, the sequential readout from the sensor will be rather slow. Any camera shake during this time means that the image gets a "wobbly" look.

Below are four example images I took using the Lumix X 45-175mm f/4-5.6 lens at 175mm, f/5.6, 1/200s, ISO 1600:


I was holding the camera at arm's length, to get pronounced effects. Even with a shutter speed of 1/200s, which one would normally think is safe with this lens at 175mm, there are heavy rolling shutter artefacts.

So, in this example, I exaggerated the effect by holding the camera at arm's length. But with normal use, I often note similar effects, although less pronounced.

Measuring the rolling shutter

It's easy to forget that the mechanical shutter is also a rolling curtain type shutter. It just moves so quickly that it behaves like a global shutter for most practical purposes.

We know the speed of the mechanical shutter. The camera's flash sync speed is 1/160s. That is the slowest shutter speed in which the whole sensor is exposed at one time. This means that the shutter curtain travel over the sensor at 1/160s, or probably slightly faster for some margin of error. So let's say around 1/180s as a guesstimate of the mechanical rolling shutter speed.

What about the electronic rolling shutter speed? Based on the example images, we know that it is slow, but just how slow? To measure it, Technic Lego again comes to the rescue.

I made this rotating propeller setup. The yellow propeller rotates exactly nine times faster than the red part to the right. By video recording the rotation, I find that the red part rotates twice per second, meaning that the propeller rotates 18 times per second:

Since the yellow propeller is three-pronged, this means that one single blade passes 54 times per second.

To illustrate what an "ideal" picture would look like, I take an exposure using the mechanical shutter first. It turns out like this, 1/1000s, ISO 6400:

So even using the mechanical shutter, we get some rolling shutter artefacts. We just need a very fast moving item to see it. This reminds us that the mechanical shutter is not a perfect global shutter, in fact, it is also a rolling curtain type shutter.

And based on this image, I can try to estimate the speed of the mechanical shutter. The blade has moved around 30° during the exposure. This is 1/12 of a full circle, and the blade rotates 18 times per second. This makes 1/216s passing during the rolling shutter movement. Since the flash sync speed is 1/160s, my estimate makes sense. The shutter is probably slightly faster than the flash sync speed. So my method appears to have merit.

What remains then, is to photograph the upper part of the propeller using the electronic shutter, and count the number of times it passes during the exposure. Here is one example image, taken at ISO 1600, 1/250s, f/2:

A propeller blade passes just above five times, let's say 5.2 times, just to name an estimate. Knowing that one single blade passes 54 times per second, this means that the electronic exposure takes 1/10s. Hence, the flash sync time using the electronic shutter, if it was possible to use the flash, would have been 1/10s. Which is very, very poor. This is the reason why we get the horrible rolling shutter artefacts.

By the way, this is consistent with an interview I read with some Panasonic engineers. They said that the electronic rolling shutter speed was about 0.1s, which is what I measured as well.

Compared with the GH2 electronic shutter

The Panasonic GH2 also has an electronic shutter option. However, it only gives 4MP images at the maximum. My study here reveals that the rolling shutter properties of the electronic shutter mode is exactly the same as the video mode. Hence, it is my belief that the electronic shutter in the GH2 simply takes the video output. That explains why the resolution of the 4MP images are poor, even for a 4MP image. It also explains why the GH2 could not produce images larger than 4MP when using the electronic shutter: This would have required an additional sensor readout process which was not yet available, until the G5 came along.

Comparison with other systems

The Nikon 1 mirrorless cameras were designed with electronic shutter in mind from the start. The Nikon 1 S1 10MP camera has a 1/60s readout, six times faster than that of the Panasonic GH3. The Nikon 1 J3 14MP camera is even better, with an electronic shutter capable of reading the whole image during 1/80S.

Only the Nikon 1 V2 camera features a mechanical shutter at all, usable when you want to be sure the image comes out without any rolling shutter artefacts. Further, the camera can take full 14MP images at a staggering 60FPS rate using the electronic shutter, opening up for very interesting uses.

From the Sony NEX line, some of the recent cameras, e.g., NEX-5R and NEX-6 have an electronic front curtain shutter. This means that the mechanical shutter is not closed prior to the start of the exposure. The only mechanical shutter is the one which closes when the exposure is stopped, the rear curtain. The advantage is obvious: It reduces the vibrations before the exposure commences, and also reduces the number of mechanical movements overall, while still avoiding the rolling shutter artefacts discussed above.

Conclusion

The electronic shutter feature is very interesting. But it's usefulness is limited, since it requires that both the target and the camera are very still. You must keep the camera still for 1/10s, which is pretty much impossible. However, when photographing organic objects like nature or people, small wobbly effects will probably not be noticed. Photographing geometric objects using the electronic shutter can be a problem, though.

Panasonic is marketing this function to be used for action photography. Here is a part of a screenshot from panasonic.net regarding the Panasonic GH3:

From panasonic.net, image copyright Panasonic

However, I doubt that those images could have been taken using the electronic shutter mode, as the movement would have caused significant wobbling effects. They could be video captures, though, as the video rolling shutter artefacts are much smaller.

Despite this, I think the electronic shutter mode of the GH3 is quite interesting, and I use it a lot myself. Unless you are photographing very square objects, like urban architecture, and especially when using a long lens, it is a very good feature to have.

You could even turn the electronic shutter to your advantage, and use it for creative purposes. Here is a picture of a moving car. Since I used the electronic shutter, it appears to lean backwards, while the rest of the scene is the right way up:

This way, you can recreate the famous photo of a racing car taken in 1913 by Jacques Henri Lartigue using a 4x5 Speed Graphic camera:



The shutter moves relatively slowly on this camera almost 100 years old camera, when compared with modern SLRs, which gives the distortion of the racing car. The distortion is especially visible in the wheels, which appear to be leaning forward. This effect was later copied by cartoonists when they wanted to give the impression of speed.

To get the same effect using the GH3, you need to hold the camera upside down. Otherwise, the car will lean backwards.

Real life example

This picture was taken at dusk, at f=28mm, 1/13s, ISO 1600, f/3.2, with the electronic shutter mode. I was panning with the movement of the car to keep it sharp, while blurring the background:

Since I used the electronic shutter, the background buildings are a bit skewed in this picture. They appear to be leaning to the left. This is due to the rolling shutter effect. Had I used the mechanical shutter, the image would have become exactly the same, except that the buildings in the background would not have been skewed. So, is this effect a problem? Not really. I doubt that many would notice the skewed buildings in the background. Perhaps you could say this even makes the image more lively. So my advice is: Unless you are using a very long lens without a tripod, or taking pictures of architecture, go on and use the electronic shutter.

There are more GH3 electronic shutter examples here.