attached image Lisa Eadicicco
LG boasts its newest smartphone, the LG G4, has the widest aperture available on any US smartphone.

But what does that mean?

The LG G4 comes with a 16-megapixel rear camera with a f/1.8 aperture. In photography jargon, the "f" before a number is short for F-Stop, which is a way to measure how wide or narrow a camera's aperture is.

The smaller the number after the "f," the wider the aperture, and the more light can hit the camera's sensor.

This has several benefits, like shallower depths of field so you can have subjects pop out against a tastefully blurry background. Most importantly, perhaps, is that larger apertures result in clearer, sharper shots with more detail in dark environments.

An example of shallow depth of field.
Flickr \ David J Dalley
In theory, the G4 should be able to capture better still shots in low-light situations than the Galaxy S6's f/1.9 shooter, and it should snap shots with shallower depths of fields, too. However, we took some low-light test shots earlier this month with the Galaxy S6 and the iPhone 6's f/2.2 camera, and the results were very close. So, despite LG's claims, we have our doubts about how much difference an f/0.1 wider aperture can make.

Here's a photo taken with Samsung's Galaxy S6 in low-light.
Business Insider
But wider apertures and more megapixels don't necessarily translate to sharp, well balanced pictures in bright environments. The iPhone 6, for instance, has an 8-megapixel camera, while the Galaxy S6 features a 16-megapixel camera — and yet, test shots revealed similar sharpness and clarity, despite the S6 having double the megapixels.

The size of the image sensor matters, too: Bigger is usually better.

The LG G4's rear shooter features a 1/2.6-inch sensor, upgraded from the 1/3-inch sensor in the LG G3.

Other smartphones with 16-megapixel cameras and 1/2.6-inch sensors include the Samsung Galaxy Note 4, which performed well in our test shots, but not quite as well as the iPhone 6 Plus, which had a smaller 1/3-inch sensor. Pixel count and sensor size aren't absolutes: What matters most is the balance of these features and how well they work with the software.

An example of the light trail effect, made possible with shutter speed control.
Flickr \ Stokeparker
The G4's camera app has a "Manual Mode" that gives G4 owners D-SLR-style functionality, including RAW image capture that lets photographers take pictures without any added processing from the phone's camera software. Another feature you won't find on most native smartphone camera apps is shutter speed control for shots withlight trail effects. Yet, only test shots with a G4 and comparisons with other leading smartphone cameras will reveal which has the best camera.