65" to 72" away. You can set it further back than that, but that will cause the light to be further away from the subject and therefore creating a darker image. You can adjust this by setting Av: to 8.0 or lower and/or increasing the ISO to 800 or 1600. Increasing the ISO will cause a loss of quality in your images. I don't suggest going higher than 800 if you're using the Canon T3i.