The New Google Camera has just hit the play store which brought a list of changes to the stock camera app for users that were already on it, and brings a whole bunch of new things to people that didn't have the stock camera app prior to today, among them a new Lens Blur mode and the ability to create photosphere images for non-nexus devices. One of the things that appeared to have gone missing is the manual exposure feature, when in fact it was just sort of hidden within the settings. If you like to mess with the exposure for your shots, you can still do so, but now have the ability to toggle manual exposure on or off.
To get to this toggle switch, all you have to do is open the Google Camera, then swipe in from the left edge towards the center, to bring up your list of varied camera modes. Once you do this, the settings button will appear in the top right corner of the UI, and you'll want to tap that to enter the settings menu. Once inside settings, not only will you find the resolution and quality configurations-which contains the toggles for the low and high quality lens blur effect mode-but you'll also see the advanced settings menu, which is where you want to go.
Enter advanced settings and you'll find the one lonely option of toggling on or off manual exposure, which will allow you to let in more light for your shots, or block more light out. Now that you've turned the toggle on, if you go back to the camera viewfinder, the menu button-three dots in the top right corner-you should see the manual exposure feature all the way at the bottom just below the grid option. That's all there is to it. The feature is easy to get to so if you decide you'll never really end up using it and would rather just end up turning it off, you can go back to advanced settings within the regular settings menu and toggle the switch back to off to get rid of it. We wonder why Google decided to turn this into a feature that the user could turn on or off, as the setting for the exposure was always automatically set to zero and seemed to manage the exposure on its own already.