How to adjust camera brightness on iphone?

I'm just curious as to if there's a way I can add a slider to adjust photo brightness when using the camera on an iphone?

If your talking about the flash, there's no way. If you want to change the picture while taking it… You tap the screen on a light place, the screen the picture will get darker, if you tap the screen on a dark place, the picture will get lighter. (But of course the dark picture thing won't work when your in a pitch black room). This is for either view, front or back camera works either way. Remember, you use your finger and just tap the screen