The Asus Zenfone 3 ZE552KL uses a Sony IMX298 sensor, which we've seen on high-end phones like the Huawei Mate 8, OnePlus 3 and Xiaomi Mi 5. The 16MP sensor is behind an f/2.0 lens and is backed by an impressive number of assistants. For example, it has a color correction sensor on the back, which makes white balance much more accurate (we've seen LG use this to great effect).
The sensor does the usual contrast and phase detection autofocus, but there's a Laser AF system too, which gets centimeter-level accuracy (~0.5") at distances up to 1.5m (5ft). There's tracking autofocus as well, all of these come together to get a focus lock in a mere 0.03 seconds.
The camera boasts a 4-axis optical image stabilization along with 6-axis digital stabilization (most OIS systems can't correct roll, EIS can).
Real time HDR makes sure the preview you see in the viewfinder is an accurate representation of the final image you get. There's a 4x Super Resolution mode, which produces a 64MP image (it takes multiple exposures, so the quality is higher than a simple upscale).
There are plenty of shooting modes, thankfully the toggle for Manual mode is available right on the viewfinder. It shows a horizon level, a histogram, a reading for the exposure compensation, ISO and shutter speed (if you haven't set those manually). The Zenfone 3 can vary its shutter speed from a time-freezing 1/50,000s to 32s, suitable for light paintings.
Manual mode can't change the aperture, but there's a dedicated Depth of Field mode, in case you're in the mood for some bokeh. Selfie mode uses the main camera and automatically snaps a photo when it detects the right number of faces (you can tell it from 1 to 4 or more). All Smiles and Children modes also use face detection - the first takes 5 shots and composes the best result from each, the second automatically snaps a photo when it sees a child's face (there are some sound cues to attract the kid's attention too).
Additional modes include Low Light (takes a 3MP or 4MP photo, optimized for very dark scenes), Night mode (low light shooting at full resolution), Smart remove (delete moving objects), Time Rewind (burst mode), GIF animation and Time Lapse, several others too.
The Asus Zenfone 3 ZE552KL camera produces sharp and detailed 16MP photos. Colors are beautiful and white balance is always spot on. Noise is kept under control (only fine grained monochromatic noise is visible if you pixel peep), noise reduction doesn't rob photos of their detail (even foliage and grass look good).
Our one concern is the dynamic range - the camera often overexposes parts of an image, which is sometimes combined with underexposed dark areas. We turned to HDR and found that both Auto and On modes produce the same image (that's not true for all phones). HDR mode does indeed resolve most issues of dynamic range, but the cost in quality is very high - images turn smudgier as if the noise reduction had to work ten times harder.
We tested out the low-light capabilities of the Zenfone 3 and found that the Auto mode does quite well. Sure, the noise increases noticeably, but there's no color noise. We tried out Night mode (full 16MP resolution), but all that did is lower the shutter speed (from 1/13s to 1/6s) and the image became softer (note that we used a tripod to eliminate hand-shake). The Low Light mode downscales photos to a quarter of full resolution (3MP if you want 16:9, 4MP if you do 4:3) and though that lowers the noise levels, it also leaves detail on the table. We're not sure the trade-off is worth it.
The Zenfone 3 ZE552KL comes with an 8MP selfie camera, which also has an f/2.0 aperture. The selfies turn out sharp and with very little noise. The focus is at an arm's length, so the subject is sharp while the background is softly blurred.
The panorama mode produces fairly high resolution images (around 1,900px tall). Other than the fast-moving cars, stitching is flawless and the panoramas are detailed. The dynamic range proved not to be an issue.
The Asus Zenfone 3 ZE552KL can record 2160p videos with its main camera, as well as 1080p @ 60fps clips. The selfie camera does 1080p @ 30fps.
All videos are recorded with the H.264 codec, so you shouldn't have issues sharing them. The audio bitrate is a bit low - 96Kbps for stereo (48kHz sampling rate).
The 4K 2160p videos are shot at a high 42Mbps bitrate, but there's something off - a barely noticeable flicker, most visible in areas rich in detail. And the videos are indeed rich in detail, but standing close to a 4K TV you will notice the flicker (at a distance it's much less of an issue). Colors are again spot on.
1080p footage is shot at a higher than usual 20Mbps and is free of the pesky flicker. The video quality is great, you only lose a bit of the field of view. Going to 1080p @ 60fps makes the image noticeably softer, it looks halfway between 1080p and 720p.
Slow motion is available both at 1080p and 720p resolutions, but there's a difference in the final frame rate you get. At 720p, the camera manages a passable 22fps, but at 1080p it drops to 15fps, which is very noticeably choppy.