The LG G3 Review

Camera Architecture

For those that are familiar with the LG G2’s camera, much of this will seem like old news. After all, OIS and a 13 megapixel camera are both things that have already been done, but LG did focus upon adding new elements to the camera system that are well worth investigating. The key new features this go around are laser autofocus, and OIS+. It doesn’t appear that anything significant changes between the G2 and G3 in terms of optical stack. As far as I can tell, the LG G3 does appear to be using a new front facing camera, as the Sony IMX208 is a sensor that I’ve never heard of before. There’s not a lot of public information on this sensor, but we do know that it has a 1.4 micron pixel size and 2.1 megapixels. I’ve put the details on the G3’s camera system below in a table. Outside of the camera itself, LG has also added a dual-tone LED flash much like the system on the iPhone 5s and One (M8), which improves color rendering when the flash is on. This means that the flash can complement the lighting of a scene rather than fighting it.

The first “new” feature isn’t actually particularly new, although we’ve learned more about it since it was first announced. The LG G Pro 2 introduced OIS+, which was stated to be OIS with EIS to improve stabilization. The LG G3 uses the same OIS+ system, and we now know that the plus at the end indicates that the camera is now stabilized along the z-axis. In practice, the effect is rather subtle, although it’s clearly there. Overall, the image stabilization locks on to target better than before. LG leverages this to achieve a maximum integration time of 1/9 seconds. Low light will also push ISO/sensor gain as high as 2900.

The actual new feature is the laser autofocus. While I talked about it back in the launch article, I’ve gained a more nuanced understanding of the system. The laser appears red to my eyes, but a camera with a poor IR filter sees the laser as purple, which suggests a spread of spectrum rather than a single wavelength. This system is likely to be a much more refined version of a proximity sensor. While it’ll take a more nuanced look at focus latency, subjective testing shows that the G3 is very fast to focus on low contrast targets, and is much more consistent in its low light focus performance compared to contrast-detection based systems. I haven’t found any evidence of this subsystem in the kernel, so I suspect that this system is integrated into the camera rather than as a discrete device.

While during some initial investigation it seemed that the G3 might actually use the IMX214 sensor, after some more digging it’s clear that this is using the Sony IMX135. I suspect that LG may have considered using this sensor at some point in the past but changed the spec without changing the software. Despite this, it's worth going over what the advantages of the IMX214 are. These advantages are effectively summed up with reduced z-height requirements, better sensitivity, less color crosstalk, and true video HDR. Reduced z-height requirements are a function of the better light collection capabilities despite off-center collection angle. Better sensitivity was also achieved by reducing the distance between the microlenses and the photodiode on the sensor. This same change also reduced the amount of color crosstalk, so this means that the red pixels will have less blue or green light detected and so on. Finally, the upgraded sensor means that two different exposures can be taken simultaneously for video HDR integration. Sony states that this new sensor can do this HDR combination up to 13 megapixels at 30 fps, 2160p30, or 1080p60. The IMX135 is still capable of doing the same at 1080p30, so I suspect that there wasn't enough improvement from the IMX135 to the IMX214 to justify a more expensive sensor.

To see how well this new system really performs, we have to turn to our array of camera tests. This will also serve as a good benchmark for how LG has improved image processing in general, as the OEM has a significant impact on the final image quality. This is because post-processing techniques done poorly such as excessive noise reduction, artificial sharpening, or failure to correct for various types of aberration can have severely impact final image quality.