Wednesday, August 19, 2009

Beware the 'Professional' Photographer

A couple of weeks ago, I arranged for my colleague Brian to test his Canon EOS 400D (Rebel XTi), with my lenses on my buried targets. Brian is a keen amateur photographer and as such likes to take control of the camera so I let Brian shoot the targets in his own way. The results were very mixed and even using the Sigma macro lens (which gave the best results), Brian didn’t capture many auras and most shots just resulted in a ‘noisy’ blank. Strangely, shots of the same target produced auras on one shot but blank on another. My own experience was that if a target produced an aura once, all things being equal, it would produce an aura every time, so I went for a lie down in a darkened room to contemplate the problem…
Although I’m a technician by trade, I like to keep things simple especially with complex instruments like DSLR cameras so I put my camera on automatic and just point and shoot, letting the camera take care of everything, including focusing. Brian had set his camera on automatic but was pre-focussing without the IR pass filter in place (so the focus would lock on visible light), compared to my method which was to autofocus through the IR pass filter, and effectively focus on infrared light. Brian returned to retest his camera using the standard lens and autofocus through the IR pass filter. The results were great --The picture shows the aura on a single British gold sovereign coin. I used Brian’s camera hand-held and achieved an aura on all targets except the three aluminum beer cans; Brian used the camera hand-held and tripod-mounted and achieved auras on all targets. Brian achieved slightly better results than me, with tripod-mounted producing the best results and I put this down to operator technique – the more stable the camera is held the better the results.
A couple of other interesting facts emerged from these and other recent experiments. 1) The auras have definitely become stronger over the two years that the targets have been buried. 2) I removed the four gold coins for the benefit of the video and did not re-bury them. One week later we were still getting a faint aura over the empty hole.