I borrowed a SB-900 and
made some flash experiments.
You are welcome to check my results.
The Legend below shows my D300 with 18-135 lens.
I used SB-400 too so you can see the difference.
The candela setup has been explained in previous posts.
I used a dark room, distance to the candle is 1 meter.
The ceiling is light orange (about html bg cc6633) color.
This causes the orange nuance in some flash pics below.
See e.g. left down where SB-400 head points upwards.