Olympus E-M5 II shutters

The Olympus E-M5 Mark II introduces a number of firsts in Micro Four Thirds: In-body image stabilization usable for video recording (tested here), high resolution mode (tested here), and the first Olympus camera with an electronic shutter mode. In this article, I will compare the shutter modes of the Olympus E-M5 Mark II.

Electronic shutter mode was introduced with the Lumix G5 camera in 2012. The same Lumix G6 and Lumix GH3 shared the same electronic shutter implementation, which has a significant drawback: The sensor is read during a rather slow period of 1/10s second, which can lead to significant rolling shutter effects.

The Lumix GH4 (my review) improves upon this with a 1/30s sensor output, on the other hand, it only uses 10 bits depth in electronic shutter mode, which can give you less effective dynamic range.

These are the shutter modes available on the Olympus E-M5 Mark II:

	Normal mechanical shutter	This is the usual shutter mode, which has been implemented on all Micro Four Thirds cameras so far: The exposure starts with closing the curtain shutter completely, then opening it again for the start of the sensor exposure, and closing again after the desired shutter speed. Finally, the mechanical shutter opens again for live view.
	Electronic first curtain shutter (anti-shock)	Compared with the normal mechanical shutter mode, this setting gets rid of the first curtain cycle, hence the name "electronic first curtain shutter". This avoids the shutter-shock associated with the first mechanical curtain closing, which is why it is often referred to as the "anti-shock" mode. This mode does not work for shutter speeds faster than 1/320s. If you use a faster shutter speed, the camera will automatically use the normal shutter.
	Fully electronic shutter (silent shutter)	In this mode, there is no mechanical shutter travelling at all, and hence, the shutter is completely silent. You may still get some noise, due to the lens focusing, or due to the lens aperture closing down upon the exposure. The fully electronic shutter works with any shutter speed. From 1/16000s down to several seconds.

Here is a high speed recording of the two variants of the mechanical shutter. The video recording was done using the Nikon 1 V3, which can record videos at 1200 frames per second.



We see that when starting and stopping the exposure, the shutter opens and closes during three frames, meaning that it takes around 3/1200s, or 1/400s. This is sufficient for the flash sync speed of 1/250s.

Bit depth

To speed up the electronic shutter readout, some Micro Four Thirds cameras reduce the sensor output from 12 bits to 10 bits. This reduces the dynamic range. Is this also going on with the E-M5 Mark II?

To test this, I have taken the same picture using the Olympus E-M5 Mark II, Lumix GH4, all using both the mechanical and electronic shutter modes. The photos were underexposed by two stops, to make the rendering of the shadows more challenging.

All the pictures were taken at ISO 200, the base ISO for these cameras:

	Mechanical shutter	Electronic first curtain shutter	Electronic shutter
Olympus E-M5 Mark II
Lumix GH4

Looking at the JPEG output images above, there is little difference to find, beyond some unintended differences in the exposure. However, when I process the RAW files in Silkypix, increasing the brightness by three stops, I find some difference in the shadows:

What we see here is that the Lumix GH4 image quality is pretty much reduced when using the electronic shutter. You lose some effective dynamic range when using the electronic shutter mode of the GH4, compared with the mechanical shutter. There is more noise in the shadow areas.

This is because the GH4 is designed to use a 10 bit output in electronic shutter mode, to speed up the sensor readout, rather than 12 bits with the normal shutter. Less bit depth effectively means less dynamic range, and more noise in the shadow areas.

The Olympus E-M5 Mark II, on the other hand, appears to use the same sensor readout in both mechanical and electronic shutter mode. So you don't need to worry about losing the dynamic range when using the electronic shutter.

Speed of E-shutter readout

The Lumix GH3 electronic shutter had a readout speed of 1/10s, which is very slow. This leads to significant rolling shutter artifacts, that you can read about here. How does the Olympus E-M5 Mark II compare?

One way to test the speed of the electronic shutter is to take a photo at a fast shutter speed in artificial light. For about a century or so, people have been using incandescent light bulbs for electronic indoor lightning. Even when used on alternating current (AC), the light is stable. Since the filament is heated, it emits light also when the alternating current is at zero.

However, traditional incandescent light bulbs are now being replaced with the energy saving fluorescent light bulbs. They tend to flicker at 100Hz (in Europe) or at 120Hz (in the US). The lights don't flicker at 50Hz and 60Hz, as you might expect. This is since during each period, the electrical current reaches two peaks, see the illustration below:



Here are images taken at ISO 3200, 1/400s with both cameras:

Olympus E-M5 Mark II	Lumix GH4

These results are quite easy to explain. With the Lumix GH4, I get about 3.3 stripes horizontally. Each stripe corresponds to 1/100s, hence, the total exposure takes about 1/30s.

The Olympus E-M5 Mark II has a slightly slower electronic shutter. There are about four stripes in the image, which means that the exposure takes 1/20s.

The slow electronic shutter means that you need to be careful when photographing moving objects, or when using a long lens without a tripod. But this effect is not only a problem, you can use it creatively too. Here are a couple of "cute" example images taken using the electronic shutter mode on the Olympus E-M5 Mark II:

Skewed cars moving at speed. Hold the camera upside down to make them lean the other way. Sigma 60mm, f/2.8, ISO 200, 1/1250s:

Bass string appears to move in a wave pattern, due to the rolling shutter effect. Sigma 60mm, f/2.8, ISO 800, 1/800s:

These two pictures would be impossible to take using the normal mechanical shutter.

Conclusion

The Olympus E-M5 Mark II introduces the very useful fully electronic shutter mode to Olympus cameras. This allows you to take truly silent pictures, and avoids shutter-shock.

On the other hand, the exposure goes over 1/20s, even if the shutter speed is faster, meaning that you must avoid photographing moving objects. Unlike most Panasonic cameras, Olympus did not compromise on the image quality when using the electronic shutter mode, meaning that you don't get the (very slight) reduction in dynamic range with the electronic shutter.