Today's theme is distance, scale and DOF. After having downloaded a super free application called iSee4K for the iPhone which lets me calculate DOF on the go, I thought I might apply it. So for this set-up, I calculated my height, divided it by the length of the sensor and multiplied it by the focal length of the lens to determine that I would need to stand 5 meters from the (estimated*) central nodal point of the lens in order to fit in frame at a 100mm focal length, and then further calculated that at f/2.8 I would have around 20cm focus either side of me, which is more than sufficient to keep me in focus but also give the background some blurring. I then set the ISO to 50 and bounced an off-camera 580 EXii at half power off the ceiling about two-thirds of the distance from the camera to me. And it worked – hence the smug, but slightly tired look!
Wanted to shoot this at 135mm, but my house just wasn't big enough.
* As my 100mm is a 1:1 macro, this was a fairly easy task. Simply measure the closest focus distance from the focal plane mark (sic) and then measure 100mm back from there. Ipso facto. This may have no scientific grounding.