Wednesday, 9 July 2014

GM1 vs Nikon 1 J1 autofocus during video comparison

Looking at the Nikon 1 J1 and Lumix GM1, it is clear that they are very similar:


Both are quite compact mirrorless cameras without a grip, without a flash shoe, and with fixed LCD screens. You can't put an eye level viewfinder on any of them. Both are mounted with rather similar wide angle pancake lenses in the picture above.

Also, since the Nikon 1 J1 is the very first generation mirrorless camera from Nikon, and the cheapest, it may look strange to pitch it against the Lumix GM1, which is a new, premium camera from Panasonic, widely seen as the leaders in large sensor video.

However, the Nikon 1 family of mirrorless cameras has something which Panasonic has never implemented: On sensor PDAF sensors. Panasonic have decided to rely on CDAF, which requires more image processing power to function well, but has the advantage of not sacrificing any pixels for PDAF sensors. In theory, PDAF should be able to give a much better AF-C performance, and AF performance during video recording.

You may also think that the Lumix GM1 is not a very good video camera, as it appears to be styled in a classic way. However, in my experience, it performs just as well as, or even better than, the GH3 in terms of image quality, quality of ETC video, and AF during video. So the GM1 is pretty much state of the art, except for the fact that it doesn't have 50/60 FPS 1080p video, and of course, it doesn't have 4K video.

To see how the Nikon 1 J1 camera performs in terms of autofocus, I mounted both to a Desmond Mini Dual Camera Bracket, typically used for stereo photography. The lenses are the Lumix 14mm f/2.5 and the Nikon 1 10mm f/2.8. I set both lenses to f/2.8.


For the test videos, I set the ISO to 200, except when otherwise noted. Here are the results:





As you see, the Nikon 1 J1, despite being two years older and cheaper, is way better in terms of acquiring focus. Even when panning quickly, it gets the focus right almost instantaneously, and even in poor light and high ISO.

I would say that Nikon is the only company which got PDAF for mirrorless cameras right from the beginning. The AF performance is just amazing.

Now, these videos are not typical of how people normally use video, but they illustrate the strength of the Nikon 1 system. Also, the 27mm equivalent wide angle pancake is not the one which needs fast AF the most.

However, with the recently launched Nikon 1 70-300mm f/4.5-5.6 lens, the Nikon 1 system will be the first to be useful for birders.

At no time before has there been a so small and light interchangeable lens system with this reach: More than 800mm eqvivalent. And with the fantastic AF performance of the system, this lens should be useful for catching birds in flight (BIF). Especially with a camera like the Nikon 1 V3, which has a proper grip and EVF.

6 comments:

  1. Wow, the AF of the Nikon is stunning. It would be interesting to see how well the GH4 does in comparison.

    Thanks for another great post.

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    1. The GH4 does focus faster than the GM1. But the difference is not huge. The 2.5 years old Nikon 1 J1 still wins by a big, big margin.

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    2. Thanks for the update, shame that the GH4 can't compete with the Nikon 1 J1. Maybe the GH5 will? Let's hope so.

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    3. It appears that Panasonic are committed to using CDAF only, not PDAF. Their DFD technology, which is an old method, helps on the GH4, and will probably be further refined on the GH5. But it can only create fairly small, incremental improvements.

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  2. (tried to post this earlier, looks like it didn't go through)

    One small remark, the Nikon 1 sensor is a bit smaller, so the depth of field is shallower at the same aperture (it can be seen at time 0:27-28 in your video: both the wall and the background are almost in focus on the Nikon, while it's more blurred on the GM1).

    Looking at this website: http://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator/#fmt=3&ap=2.828427&fl=10&dst=5&u=m , the equivalent of 10mm f2.8 on Nikon 1 is 14mm f4.0 on m43 (so you got the right lens, but you should close down the apperture a bit more on the GM1 for a fair comparison).

    I'm not saying this fully explains the difference, but I guess a shallower depth of field does not help the GM1...

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    Replies
    1. Yes, the depth of focus if slightly deeper with Nikon 1. But the difference is barely noticeable.

      When I look at for example 0:25, I see the foreground in focus, and the background out of focus with both cameras. The Nikon 1 background image is slightly less out of focus, but the difference is small.

      The difference in DoF does not explain the results here, Nikon 1 is simply a lot better at focusing.

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