My iPhone 5s takes perfectly clear photos when I access and use the stock Camera app to take a photo. However, if I try to use the camera in an app, e.g. to use the camera in my banking app to deposit a check, the photo is too blurry to use. I have found this is the case with all apps that use camera other then the Camera app.
Sometimes, even when we have tried "everything," a reset of the device can help. This 'reboots' the phone.
Hold the Home and Power buttons down at the same time until the logo comes back to the screen. (The screen will go black, keep holding.)
Let go of BOTH buttons when the logo comes back. (Continuing to hold the Home button will put the iOS device into Recovery Mode)
Recovery mode will re-download iOS and then give you the option of restoring from a backup.
If this doesn't work, and a restoration of the phone from scratch in Recovery Mode (which is time consuming for the download) doesn't work, if you iPhone is under warranty see if Apple will be able to help. They want you to be happy and will do what they can within reason.
From a thread in Apple support community:
Soft = Turn phone off and on. Hard = BOTH buttons held until you see Apple Logo.
Difference: I like to explain by thinking of a laptop. On a laptop (or even computer) you can go to hibernation mode (memory gets written to disk then powers down). When turned on, it loads back up from memory and thus everything that was loaded in memory before shutting down is put back. That is what a Soft reset is (when you do the power button the slide to turn off). Thus if there was a memory leak for example in some program causing issues (sluggish, crashes, etc)....then if you just turn off and on, it will still have issues. A hard reset is like pulling the plug on your computer. It will have to turn back on and reboot fully. It does write an error log out to itself (nothing you see) but causes no harm to your phone or data. It is just a way to do a full clean boot up. This actually fixes about 90% of the issues most people have.
Has no effect on battery outside of the fact it has to boot up thus processor and read writes will be happening.