Hi,Thank you for using Just Answer my name is Carl and I will help with your question.I am sorry but I am unable to help you fix the fault, you will need to contact Samsung to look at returning the phone to them. Samsung have acknowledged that there is a fault with some S5 cameras.Please http://www.androidcentral.com/some-users-report-galaxy-s5-camera-failures
Please see herehttp://www.androidcentral.com/some-users-report-galaxy-s5-camera-failureshttp://www.droid-life.com/2014/04/25/samsung-acknowledges-galaxy-s5-camera-failed-issue-verizon-issuing-replacements/
If you have the phone on a contract I would contact your service provider first as I am sure they will be able to arrange a replacement.
I am sorry I cannot help more but it looks like it is a hardware or software fault with the phone. If it is a software fault I am sure Samsung will release a software update to solve the problem soon.