Is there a rule of thumb in selecting between the MR11 and MR16 bulbs? I understand that the MR16 is larger and has more light output but I’m struggling to quantify that difference. For what it’s worth, I have 3 trees which at mature height will each be less than 15 feet tall. I’m planning to use a Salty Dog In-Grade Light (Shielded) on each.
I'm a fellow lighting enthusiast. One approach that might work is for you to look at the difference between 15W, 25W, 40W incandescent bulbs in the dark. For your needs, you want to consider brightness, beam spread, and color temperature options. While the MR11 can create many of the same effects and outputs as the MR16, the MR16 is significantly more customizable wrt the variables I listed. The least bright MR16 (2W) option is a 15W incandescent equivalent whereas the least bright MR11 option is a 20W equivalent. If that 20W is as bright as you need, and it's available with the beam spread, and color temperature copy options you need, then the MR11 fixture should work for you. If you think you'll want to choose from among a wider range of beam spreads, lumens levels, and color temperatures, then you'll probably be better off with the MR16. HTH
