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.
When Panasonic released the GH3, it was expected to raise the bar even further in terms of video quality. To compare it against the GH2, I connected both cameras to a piece of wood, using Manfrotto Superclamps, so that they would record the same scenery for comparison.
On both cameras, I used the Lumix G 14mm f/2.5 pancake lens, a favourite of mine. I focused on "infinity", and then set both cameras to manual focus. The lenses were set to f/5.6 for the best sharpness, and I used the base ISO on both cameras. With the ambient lighting, the shutter speed was usually around 1/120s. Both cameras had the same settings in terms of sharpening and saturation. It was all recorded in 1080p, 25fps.
Here are the videos combined, for easy comparison:
Some may doubt that the quality of the YouTube rendering of the video is sufficient to really tell the difference between the cameras. I agree with that, and to assist in comparison, I uploaded parts of the video at 200% size, which probably makes the video image quality easier to assess. And I made some 100% crops from the original out of camera video files, uncompressed in PNG format below:
This last image comparison is from the ISO 1600 footage:
Conclusion
Just like I have concluded previously, the GH3 features somewhat less rolling shutter artefacts in video mode. Further, I think it looks like the GH3 handles high contrast better, and the overall sharpness of the video stream is better. Not unexpected, since the GH3 can record at up to 72Mbps bitrate, as compared with 24Mbps for the GH2. I used 50Mbps with the GH3 here, though. Of course, the bitrate is not everything, the sensor, AA filter, downsampling algorihm and compression algorithm are also important.
I also like the colours of the GH3 better. At high ISO, the GH3 does provide more details.
As far as I can see, the GH3 does deliver on the promise of delivering even better video quality than the predecessor GH2.
Here are some example images, taken with the electronic shutter, the mechanical shutter, and a still image from the video output:
Electronic shutter (f/1.7, 1/250s, ISO 200):
Mechanical shutter (f/1.7, 1/250s, ISO 200):
Video still image:
We see that the electronic shutter has a slower sequential readout than the video mode. This is unlike the Panasonic GH2, which used the video output for the electronic shutter mode, and they shared the same rolling shutter properties. But then again, you only got a 4MP image with the GH2 electronic shutter mode, and it was quite unsharp, probably scaled up from 1080 lines or thereabouts.
This will be my last Panasonic GH3 related article for a while, and the review I am writing will be delayed. The reason is that I have delivered the camera for a warranty repair: The automatic switching between the LCD and EVF suddenly stopped working.
My GH1 and GH2 have operated flawlessly for years. It is perhaps ironic that the GH3 was my first Panasonic camera to require a repair, since it is marketed as being extra solid and weather proof.
Rolling shutter artefacts are typically identified when panning quickly during video recording. This can lead to "wobbly" effects, square objects can be seen to lean towards one side.
To compare these artefacts again between the GH2 and GH3, I mounted both cameras to a piece of wood:
I used Manfrotto Superclamps with ball heads to fix the cameras to the piece of wood. These are quite useful.
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.
Rolling shutter denotes a type of shutter mechanism, and can refer to both a mechanical shutter, and an electronic shutter. It also refers to the type of tilting artefacts you get when panning quickly during video recording. Some refer to these artefacts as "jello video".
This is not strictly related only to digital cameras. Older film based cameras often feature a focal plane curtain shutter, which "rolls" across the film plane and exposes the film horizontally or vertically. A very famous example of this is the racing car picture taken in 1913 by Jacques Henri Lartigue using a 4x5 Speed Graphic camera.
The shutter moves relatively slowly on this 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.
Rolling shutter is the name of a type of mechanical or electronical shutter mechanism. In this type of shutter, the whole film or sensor is not exposed exactly at once, but rather, a shutter rolls across the frame and exposes it bit for bit. Rolling shutter is also the name of the distortion associated with this shutter implementation.
You can see this distortion for example when panning heavily during video recording. It looks like the scenery is "leaning" towards one side when panning. I tried the Samsung NX10, and immediately noticed that the viewfinder had much more rolling shutter artifacts than the Panasonic G-series.
This shutter implementation also leads to distortion to rotating elements. To test which camera has the most rolling shutter artifacts out of the Panasonic GH1 and GH2, I made a simple LEGO contraption which rotates a propeller at a constant speed. Then I videofilmed this with both cameras, using the Olympus 50mm f/2 lens.
Here are the two video streams:
GH1, ISO 1600, f/2, 1/500 second, 25p, 1080
GH2, ISO 3200, f/2, 1/1000 second, 24p, 1080
To more easily compare the rolling shutter artifacts, I have made similar framegrabs from both:
What we see here, is that the distortion is slightly smaller in the GH2 video stream. The shorter the distance between the two prongs to the left, the more the distortion.
So my conclusion is that the GH2 handles rolling shutter at least as good as the GH1.
For real life usage, rolling shutter is not a problem with GH1 or GH2 video. You can generate these effects by filming a rotating propeller, like I did here. Or by panning heavily. But most types of video footage will not display any noticeable rolling shutter artifacts.
As a side note, the amount of rolling shutter artifacts depend on the speed of the rolling shutter (in a mechanical implementation), or the speed of the sequential image data readout for a digital shutter. It does not depend on the shutter speed itself. Here is an illustration, where you can see three different shutter speeds generating the same amount of rolling shutter artifacts. But the amount of motion blurring is of course different.
Another term widely used is global shutter. This refers to a system in which the exposure values from the sensor are read all at once. Since the values are not read out sequentially, there are no rolling shutter artifacts with a perfect global shutter.
Before launching the GH2, a Panasonic representative was quoted saying that implementing a global shutter in Micro Four Thirds cameras is not coming soon: At the very earliest with the GH3. In retrospect, the the Panasonic GH3 did not introduce global shutter. And now, it looks like the GH4 (aka GH4K) is going to be more about 4K video than global shutter.
The "rolling shutter" concept is related to the shutter not reading out the exposure values at once, but rather scanning across the sensor vertically or horizontally. This implementation could be mechanical, as with the shutter curtain on the Micro Four Thirds cameras, or electronical, as when the sensor output is read during a video recording.
This is not strictly related only to digital cameras. Older film based cameras often feature a focal plane curtain shutter, which "rolls" across the film plane and exposes the film horizontally or vertically. A very famous example of this is the racing car picture taken in 1913 by Jacques Henri Lartigue using a 4x5 Speed Graphic camera.
The shutter moves relatively slowly on this 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.
