Category Archives: Xiaomi Yi Camera

Yi camera lens correction test

I was interested to find out what the difference was between filming with and without the Yi’s inbuilt lens distortion correction, once additional correction of the barrelling from the wide-angle lens had been corrected in After Effects.

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The images on the left are taken without the Yi’s distortion correction, and all correction in the lower image in AE, using Optics Compensation effect, FOV 74, Reverse Lens Direction on. The images on the right are taken with the Yi’s distortion correction. Further, correction in AE, using Optics Compensation effect, FOV 48, Reverse Lens Direction on.

The result (once all barrelling is removed) is very similar between the two. However, as the correction entirely in AE means that the image is being digitally blown up, a better image quality is probably obtained by using the camera’s inbuilt correction.

Additionally, when using the camera’s distortion correction the raw footage has less distortion in more distant objects. For some footage without near objects with identifying barreling features (such as straight lines), it may be possible to avoid using the AE effect entirely.

Yi camera 1 working

The first Yi camera that completely stopped working in the last test is now working when both the back of the camera has been removed, including the battery. The picture above show both front and back removed, although I have since reattached the front (which allows me to use the makeshift focus ring), and it also works like this.

Yi camera problem investigations

I have now numbered each camera (just visible on the photo in the previous post), in the order they were purchased. Each camera has a different version of the firmware, and the later two are a different model to the first.

Camera 1 Wifi: YDXJ_2326644 SN: Z23A60252326644 FW: 1.2.13 Model: 23A
Camera 2 Wifi: YDXJ_3144435 SN: Z25L630ACN3144435 FW: 1.3.0 Model: 25L
Camera 3 Wifi: YDXJ_4476443 SN: Z25L640ACN4476443 FW: 1.4.8 Model: 25L

Using the found card model on the previous post, I noted each camera’s performance. Continue reading

Found card 3 Yi test model

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In order to investigate the problems with some of the Yi cameras stopping recording, and to test the use of found materials for the models, I made a quick assembly from card from a recently purchased Ikea flat pack packaging. I will discuss the model and test filming here, and the investigation into the camera problems in the next post.

The material for the model was cellular card packing material, approx 30mm thick, small pieces of corrugated card (also from the Ikea packaging), and a piece of card from a box in which garlic bulbs had been delivered. I used a small sheet of perspex, borrowed from Alex from the front of his cabinet of curiosity (itself a form of diorama).

I used the camera mount wall from the three Yi model, so that I had ready made windows and camera locations. This meant that the width and height were the same as the three Yi model, although the depth was determined by the size of the pieces of card used for the floor surface (so slightly deeper than the previous model).

The assembly was covered in black felt to eliminate light ingress through the quickly constructed pinned joins.

I filmed with the camera’s inbuilt fish-eye correction disabled – this provided a wider field of view, but greater distortion of the image. As usual, I then “corrected” the footage via Adobe AfterEffects, using the “Optics Compensation” effect [reverse lens distortion box ticked, FOV: 77].

As previously, several of the cameras stopped working during filming (discussed further in next post). The footage below takes the complete recordings managed to be obtained from each camera, and alters their speeds so as to play within two minutes. Therefore the speed of each frame of the triptych is determined by the malfunctions of the cameras.

In the footage, the bright strip along the base of the back wall is caused by the thick perspex floor covering. I tried to cover all of the edges of the perspex to minimise this, but the effect is still there. Additionally, the use of perspex, rather than sticky film, as the shiny floor covering created very strong and sharp reflections of the sunlight. I prefer the mottled effect of the light reflected from the sticky film. I will either ensure I use this, or will source a “found” material that has a similar effect.

Third Yi Camera

I recently bought a third Yi camera to allow three simultaneous recordings. I wanted to get this while they were still available as this camera has now been superseded by a larger and much more expensive version, with round edges so it won’t stand on its short edge.

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As previously, the camera needed to be opened up to remove the glue spots holding the lens in one fixed focus.

Changing focus on the Yi camera

The Xiaomi Yi camera has its lens fixed to one focal length, which according to reviewers, was set up for hand-held selfie distances. For my use, this set focus was slightly too far, but for most reviewers it was too close as distance action shots were not in focus. Consequently, there was a plethora of sites explaining how to unfix the focus length by popping off the front facia and removing the three glue spots that held the lens in its pre-set focus. I wanted to be able to manually change the focus for different shots, so I also needed to remove the bezel around the lens so that I could continue to adjust the focus once the front facia was back in place.

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Continue reading