brightness

Hi all, I'm still very new to this, and I'm thinking of adding a 10m long straight run on my front porch. I'm thinking of going with two 5m strips of 5V WS2812 or WS2811 at 30 pixels/m. http://spikerlights.com/calcpower.aspx is showing me green if I run the lights at 50% (attached). Is this...