Whenever you would use "Portrait Mode" in iOS 10 on your iPhone 7 Plus, the camera would save both a regular and depth effect version. If you were low on space, you could always opt to save the depth effect version only, but this setting is now gone in iOS 11. While at first it seems like only the depth effect version is saved now, the normal version is still there, whether you like it or not — it's just hiding.
So the bad news is that, in iOS 11, you're forced to save both the regular and depth effect version when using Portrait Mode in the Camera app. There is no setting to opt out anymore. The good news, for those of you who liked saving the normal photo too, is that the original photo is still accessible — it's just not as easy anymore. Any Portrait Mode photos you took in iOS 10 before upgrading to iOS 11 will still be separate files on your device, just like before.
If you connect your iPhone 7 Plus to a computer with a cable, you can still see both versions of the image in Mac apps such as Photos and Image Capture. The "depth effect" label in Photos, however, will not show up anymore in macOS Sierra, but it's fairly easy to tell the difference just by looking at the photos.
On your iPhone 7 Plus, in order to unlock the normal picture, you have to go into "Edit" mode on the photograph with the effect — either from the main Photos app or when viewing the Portrait Mode image from the Camera app. Then, all you have to do is tap on the yellow "Depth" button up top and hit "Done" to save the image.
It's just like converting a Live Photo to a normal photo. And just like Live Photos, saving it as the original photo does not mean the depth effect is lost forever; You can simply go back into "Edit" mode and reinstate the "Depth" option.
The new High-Efficiency Image File Format (HEIF) in iOS 11 reduces the size of photos, such as those with the depth effect, stored on your iPhone. Theoretically, it could save up to 50 percent in space. So, if you only used to like to keep the depth effect images, you'll notice very little in storage changes, but if you liked to keep both copies before, you'll actually notice that less space is being eaten up now.
Plus, it's always good to have both copies anyway. You risk losing a good shot just by keeping the depth effect version only since Portrait Mode can't give you a perfect bokeh effect every time.
With the change to how Portrait Mode images are stored in iOS 11, who knows ... maybe we'll see a future option that lets us change the focal plane in depth effect images, similar to how "Lens Blur" works in the Google Camera for Android.