Camera
There is no doubt in my mind that the Pixel 2 and Pixel 2 XL have the best set of cameras available in a smartphone today, and that's without a second camera on the rear. What Google has managed to achieve in software is nothing short of outstanding, and it will take a lot of work by others to catch up.
The hardware used here is typical of many modern smartphones. There's a 12.2-megapixel sensor on the back, which includes 1.4 micron pixels, paired with an f/1.8 lens and optical image stabilization. OIS is new to the Pixel camera setup, which provides even greater scope for low light imagery, though the rest of the hardware is also set up for poor conditions thanks to large pixels and a wide open lens.
The key thing to note here is the absence of a secondary rear camera. You don't get a wide-angle camera like LG's phones, or a zoom camera like the iPhone. Without a secondary sensor, there's no way for Google to create depth maps via hardware, though as we'll see from the portrait mode Google has implemented, this doesn't matter at all. The only thing you're missing out is either the zoom or wide shot functionality, and considering most smartphone 2x zoom cameras I've seen provide just a minor improvement to detail, you're not exactly missing out on a lot.
The front camera is an 8-megapixel sensor, again with 1.4 micron pixels, paired with an f/2.4 lens. There's no autofocus, which is a feature we're starting to see in some high-end selfie cameras, though again, with portrait mode this isn't a big omission. The front camera is capable of 1080p video capture, while the rear goes up to 4k/30, 1080p/120 and 720p/240.
Google's image processing uses a lot of the same techniques they first deployed with the original Pixel, namely the always-on HDR that continually combines multiple burst images in real-time to create photos with high detail, high dynamic range, excellent contrast and fantastic colors. Like the Pixel, the Pixel 2 XL has the fastest HDR implementation of any camera, and while it does require some additional background processing after every shot is captured, the shutter times are effectively instantaneous. This means you can snap away as fast as you like, without having to hold the camera still as multiple shots are taken for HDR functionality.
In terms of regular image quality, the Pixel 2 XL is pretty similar to the Pixel XL. Dynamic range is outstanding, to the point where high contrast situations aren't a challenge for the phone, and at times can bring out its best performance. Unlike most other phone cameras, the Pixel 2 XL rarely delivers blown out highlights or crushed shadows; instead, you get the perfect amount of detail in both situations. And it achieves this without any weird over-HDR effects, instead preserving an excellent level of contrast that keeps photos looking reasonably lifelike.
What Google has achieved with its HDR functionality allows the Pixel 2 XL to shine in weaker conditions, like indoors or cloudy days, which is where other phones struggle. The Pixel 2 XL continually delivers excellent photos no matter how bad the lighting is, completely avoiding the cardinal sins of indoor smartphone camera photography: blur, grain, poor metering and washed out colors. None of those factors are an issue with the Pixel 2 XL.
Color performance is very good across the board, though it's clear Google has targeted 'sharable' imagery over accuracy. Metering is fantastic, so it's rare you get a photo with the incorrect white balance or exposure, though on the fly exposure adjustments are very easy within the camera app. Colors are vibrant and saturated in all conditions, sometimes to the point of being a bit overboard, but I just love what the Pixel 2 XL can do.
Detail? Again, fantastic. Google has avoided the oil painting effect, caused by aggressive noise reduction, instead managing to preserve a ton of detail without introducing grain in weaker lighting. Edges and textures look great, and when you capture a highly detailed landscape, it's easy to distinguish individual blades of grass and count the leaves on trees: no detail is lost or smudged.
The main improvement to the Pixel 2 XL compared to the original Pixel is in low light situations. The addition of OIS, combined with all of Google's multi-shot image processing, leads to astonishing results in low light. The Pixel was decent in this regard, but the Pixel 2 XL has the ability to produce brighter, more detailed, less grainy images in darker conditions. This camera is phenomenal in low light, and that adds to the strong performance in other situations.
Portrait mode is another key addition to the Pixel 2's camera. You've probably seen this feature on other cameras - it attempts to simulate DSLR-like background blur while keeping the subject in focus - but the Pixel implementation is the best. And it achieves this without additional hardware like secondary cameras. Google's expertise in software and AI has no doubt contributed to this feat, because being able to achieve fantastic results without the hardware other companies rely on is no easy task.
The Pixel 2's edge detection is far better than any other camera I've used. It nails it more often than other cameras, while preserving more detail, particularly individual strands of hair, which is a challenge for cameras that rely on depth maps from additional sensors. Thanks to superb edge detection, the Pixel 2 achieves a big distinction between foreground and background, with a suitable level of pleasant simulated bokeh. The background blur doesn't quite nail what you'll achieve with a true DSLR lens, but it comes much closer than the latest iPhones, which use an unpleasant and unrealistic background blur in their portrait mode.
The best part of the Pixel 2's portrait mode is that it works with the selfie camera as well, again without additional hardware. This makes the Pixel 2 XL by far the best selfie camera I've seen on a smartphone; portrait mode delivers stunning results that obliterate the competition.
There are still some times where portrait mode fails to properly find the edges, or fails to blur the background in a realistic fashion. But these are also issues I've experienced with basically every other simulated bokeh implementation, including those with fancy dual-camera systems. And as I said earlier, the Pixel 2 XL gets it right more often than any other implementation I've used, with better results to boot.
You don't get a manual mode with the Pixel 2's camera, which is found on competitors like LG and Samsung, or the ability to capture RAW imagery. Google probably thinks their auto mode is so good you don't need a manual mode, and in a lot of cases they're correct. However you do still get the excellent video stabilization of past Pixels.