https://www.theverge.com/circuitbreaker/2018/3/7/17091114/galaxy-s9-hands-on-impressions-questions-camera-aperture-bixby

You’ll have to hang tight for our full review of the Galaxy S9 and S9 Plus, but in the meantime, we brought the two phones onto our YouTube live show yesterday to take a closer look at them. First, we put the phones side by side with the Galaxy S8 and S8 Plus to examine the small physical differences (there’s not much, but at least Samsung moved the fingerprint reader); then we looked at the S9’s big camera upgrade; and of course, we closed out with a look at the phone’s two horrors: Bixby and AR Emoji.

The dual-aperture camera (which lets the phone better control how much light it captures) is really the highlight of the S9’s changes, but we’ve been wondering how much of a difference it’ll actually make. By default, Samsung keeps the aperture at f/2.4 — smaller and slower than other flagship phones — but the S9 can open up the camera to f/1.5 to let in a lot more light when it needs it, like at night or in dimly lit restaurants. We’ve got some side-by-side photos starting just before the seven-minute mark showing the difference between what the two apertures capture.