Changing video settings when to high

I was trying to show my friend on a high setting for minecraft on my computer. When i made it full screen the client crashed and now currently my client when i sign in or re download the game keeps going to this white screen. I know it is a graphics issue of it having to high graphics. I was just wondering if there was any way for me to lower my graphics out of the game. In any case it would be nice if there was a confirm graphics screen so this issue does not arise so other people wont get stuck like this.