Jul 23, 2015

The state of the Xiaomi Yi, China's GoPro

The state of Xiaomi Yi, July 2015

A few months ago Xiaomi, the world's third largest smartphone distributor (I know, I know--I hadn't heard of them until recently, either!), came out with the Xiaomi Yi, a $65 competitor to the GoPro line. There are many great reviews of this camera online, so I won't try to replicate what is already a large slew of videos and opinions on the camera elsewhere. Saving you some time, though: This camera is generally superior to the $130 GoPro Hero, and inferior to the $400 GoPro Hero4 lineup, falling somewhere in the middle.

High level specs

  • 1080p @ 30 or 60 frames/second, 720p @ 120 fps
  • Removable battery
  • Built-in wifi, and managed through a smartphone app for Android or iOS
  • 16 MP still images, plus other modes including burst, time-lapse photography, loop recording (i.e. dash cam)

One of the reasons for this post is that most of the reviews online are already out of date. This camera was and still remains primarily aimed at the Chinese market. This is why there is no official US distribution, and only very recently was there an iOS app in English. Also note that the $65 price I refer to is the "official" price you'll pay ordering from China (e.g. from gearbest.com). There is a $20+ markup when ordering from the US, be it Amazon or Ebay. I was lucky enough to snag mine for $65 from a US seller on Ebay.

As of July 23, 2015

  • There is an official iOS app, which works on iOS 7+ and it is in English! App version 1.10.
  • There is an image flip function; the camera can be mounted upside down and images properly flipped 180 degrees, except for the 840X480 @ 240 fps video. Camera firmware version 1.2.6.

Here are all of the current settings available for the camera. As you can see, not much can be changed about image quality (click image to zoom).

A lens cap does not come included with the Xiaomi Yi, so I took the top from a 2L pop bottle and hot glued some weather stripping foam on the inside of the cap, then spray painted it. The cap now friction-fits onto the lens and holds nicely.

Of course, the biggest problem these cameras face is the out-of-focus issue. For whatever reason, these appear to be widely set at the factory to support optimal focus at a very close range. Like any action camera, these have a very deep depth of field and, with the fixed focus, this means that focus can be good across a wide distance. However, that doesn't mean sharp focus from a few inches to infinity. Unlike the GoPro, which is factory set to "focus at infinity", with out-of-focus only at very close distances, the Yi optimizes focus for very close subjects, which means that anything at range suffers. I don't know if this affects all cameras, but it affects many. Here is a post from March explaining how to resolve it. I also had to twist my lens clockwise, though slightly less than the amount in that post at fpvlab.

I took a number of before and after focus-fix pictures. Pictures with "1" in them are the default factory focus and "3" represent the position I discovered to have the best focus balance for me. I had marked with a pen a few notches on the lens and 3 was the third notch (each was only several degrees of lens twist). The following are images taken from the camera at highest resolution (16 MP) and scaled down to 1600X1200 with the lens 12" away from the bush.

Here are various crops from these pictures. The factory default offers superior dead-center frame focus at close range, but even within 15" off center the corrected twist looks better (note the better clarity of the Precedex sticky note and mulch), and as distance increases it looks massively better.

Here are the same settings, but now with distance shots. The pebbles by the pool, the roof of the plastic play house, and the monkey bars show a sharp increase in focus on the second pic.

Those last shots invite some necessary criticism of picture quality. Although the pictures looks like they were taken at late dusk, they weren't; it was still pretty bright out. The sun was definitely going down, but the pictures suffered greatly from a fairly bright sky as the sun went down but a somewhat-darkening ground. This has always been a challenge for cameras (trying taking a picture indoors of somebody standing in front of a window, for example), but the dark ground here is quite pronounced. I did experiment with metering, which appears to have no effect on photos, so the following shots are ripped from 1080p/30fps video. The two shots above were with default, center metering. The shots below were taken with the metering changed.

Center metering:

Average metering:

Spot metering:

Something else I discovered about this camera is that when in 60 frames/second, image quality takes a significant hit. Hopefully a firmware update can resolve this, but I wouldn't hold out great hope for that. Here are image snapshots taken from 30 and 60 frames/second video. Note in particular the lost of precision of the roof on the plastic play house and also the pebbles around the pool.

I did the same thing with 720p at 60 fps and 120 fps. Unfortunately the light changes between the two pics, fudging the results. However, I think the 120p looks pretty decent.

Here is what you'll get at 840X480 at 240 fps:

And finally a shot with "lens aberration correction", which resolves the fish-eye appearance of the standard shot but loses some field of view.

To finish on a positive note, when the sun is shining brightly this camera can take pretty nice shots. Here's another image (a photo; not snapshot from video):

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