Old School RPN Perfection
My second HP-42S, my favorite calculator (I also have a 48SX that is OK, I guess). My first 42S got me through high school (math team nerd), undergraduate (engineering), and into grad school (more engineering), then it died. I was slightly freaked, as they had been discontinued a couple years before and couldn't be purchased new in local stores. Thankfully I found a source online and purchased a new one. I still use it, but only occasionally and usually for simple arithmetic. Still love it.
Nikon D90 | Sigma 17-70mm (ƒ/2.8-4.5) @ 70mm | ƒ/4.5 | ISO 200 | 1/200s
SB-80DX @ 1/128, snooted
White reflectors on right and rear left
Triggered optically via on-camera flash