There could be a number of reasons. Could be the camera hardware is faulty. Or it may be the stock camera app may be having issues, or you have an older version of the app software installed. Or, if you have more than one camera app installed, the hardware may not be connected to the app you are using. One other possibility is that when you first get the Galaxy S4, there's a protective film that's on the camera lens. You may have to remove the case to get to that protective film to remove.
The Galaxy S4 is not IP67 certified. The Galaxy S4 Active on the other hand does have that certification.
No they are to big
There's a free app you can download from the Google Play Store for that.
The Samsung Galaxy S4's screen pixel density is 441 ppi.
Yes, the Samsung Galaxy S4 is a smartphone.
Yes. They have the Samsung Galaxy S4 Active.
No, but the GALAXY S3 IS WAY BETTER!
No, the Samsung Galaxy s4 is larger than the iPhone.
The Samsung Galaxy S4 was released on April 2013.
The Galaxy S4 Active's screen is 4.55 inches.
No, the Galaxy S4 is not waterproof. If you try putting it in water, it will most likely break. You might want to consider the Galaxy S4 Active, which is a more durable, and more importantly, waterproof version of the standard S4.
No, even if you factory reset the Galaxy S4 it will not downgrade.