Sunday, 6 July 2014

Lumix GM1 mechanical shutter

The Lumix GM1 may look like a small and insignificant camera, but in fact it has some interesting innovations within Micro Four Thirds. It has two shutters: The electronic shutter, which is faster than the first generation, but still slow enough to give some rolling shutter artifacts.

Then there is the mechanical shutter. It is of the "electronic front curtain type", which means that the exposure is started electronically, without a mechanical curtain. This is good, it means that there is less risk of shutter shock, that the shutter causes camera shake and blurry images. It is also less audible, and there is less shutter wear.

The mechanical shutter is also unusually slow. While this also keeps down the noise, it is not really a good thing, of course. Due to the slow mechanical shutter, the flash sync speed is limited to 1/50s, which is a quite poor specification. This design choice was probably implemented by Panasonic to keep the size and noise down.

The slow moving mechanical curtain is possible to record using a high speed video camera.

Enter the Nikon 1 J1. Even if it was the first generation Nikon 1 camera, and the entry model, it is capable of 1200 frames per second video. At a resolution of only 320x120 pixels, this is more of a gimmick, but it can be a fun gimmick. The two cameras are seen below, both with wide angle prime pancake lenses:


One problem with video recording the moving mechanical shutter of the Lumix GM1, is that the camera will only use the electronic shutter when a lens is not mounted. So you cannot trigger the mechanical shutter without a lens mounted. This is probably for protection, to avoid jamming the curtain blades.

However, the shutter cycles once every time you power on the camera, and this can be used to record the shutter travelling.




Here is an animation showing the travelling GM1 shutter:


The shutter opens over about 15 frames, taken at 1200 frames per second in this high speed video. This means that the speed of the shutter curtain is about 15/1200s, or 1/75s. This is close to my previous measurement of the mechanical shutter speed of about 1/100s. It is also faster than the flash sync speed of 1/50s, which is reasonable.

We also see that the shutter curtains resonate a bit when moving to the fully closed position. Hopefully, the shutter curtains are dampened in a way so that this does not cause wear over time.

Conclusion


The high speed video mode of the Nikon 1 J1 may seem like a gimmick, but it could be used to produce interesting insight about the workings of the Lumix GM1 camera.

By the way, the Nikon 1 J-series of cameras do away with the mechanical shutters completely, relying only on an electronic shutter. The electronic shutter speed of the Nikon 1 cameras is 1/80s, about twice as fast as that of the premium M4/3 camera Lumix GH4 (my review).

Keep in mind that you cannot use the mechanical shutter without a lens mounted, including if you use an adapted lens, or a non-native manual focus lens. This also means that you cannot use the flash when using a non-native lens, including the body cap "toy" lenses from Olympus.


3 comments:

  1. It doesn’t make sense that it would be for protection against jamming the curtain blades as suggested in this post, since as you pointed out the camera cycles the shutter at startup, and the camera will actually use the mechanical shutter with a manual/adapted lens if you enable the flash.

    I found a great explanation for why the GM1 will not use its mechanical shutter with manual/adapted lenses over on Mu-43:

    http://www.mu-43.com/showthread.php?t=58647&p=694430#post694430

    In short, because the mechanical shutter uses an electronic first curtain, and these two curtains are some distance apart (the first on the sensor, and the second in front of it), the camera needs to know the size of the lens’s aperture and exit pupil in order to correct the relative timing of the two curtains to allow for this separation. Since the camera can’t read these parameters from lenses that do not communicate with the body, it disables the mechanical shutter under these conditions.

    This also explains why the mechanical shutter is enabled when the flash is used. The exposure is governed by the timing of the flash, not the shutter curtains, so the camera can safely use the mechanical shutter.

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    Replies
    1. Thanks! I agree that this makes very good sense.

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  2. I use your blog a lot as a reference (for myself), when I'm trying learn or remember things.

    I know this post is old, but the conclusion is in no way connected to the other part of the blog, not to mention the title. Today I found this post by Googling. Maybe you copied the conclusions from another article? Perhaps you you have the original texts / whatever so you could fix this to keep the good quality up?

    Sorry if was rude, I did not mean that. You know, English is not our native language. What comes to your blog, it's the best of the µ4/3 world.

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