I took this picture with a 105 mm on a Canon 5D DSLR so I wasn't as close as it looks -- but still too close. This snake was not active (actually kind of lethargic in the 44F morning temperatures).
This snake is one of the very few venomous snakes found at ROLF. If you watch where you are stepping and move quickly you would remain 99% safe from this variety of pit viper.
Note the elliptical eye slits.