Saturday, May 14 2011

Abstraction

I was doing some lens-testing around the house this morning, and one shot in particular struck me as interesting for laptop wallpaper.

new wallpaper

Sadly, the result of the testing was that my 35/1.4 is busted; mechanically functional, but severe circular aberration wide open, and horrible back focus. My camera’s micro-AF adjustment can compensate for the back focus, but unless I want to shoot dreamy soft-focus landscape and architecture photos, it needs fixed or replaced. Sony’s current 35/1.4 lists for $1,369, or I can send it to the last remaining authorized service center for Minolta lenses, Precision Camera, for $250. If I don’t want to eventually pitch it, I might as well get it fixed now, while there’s still someone willing to do the work.

I originally bought it used, and it never seemed quite right, but most of the time I prefer to shoot with much longer lenses, so it didn’t bother me too much. Testing it with my newly-acquired LensAlign MkII allowed me to quantify the focus issue, and direct comparison to my other f/1.4 lenses made the CA flaringly obvious. Some of my other lenses benefited from a small micro-AF adjustment, but that was 1-3 units of tuning; the 35 was so far out of spec that it needed -18 units, and the scale only goes to 20.

My previous uses had been at f/8-f/16 at 20+ feet, which mostly masked the defects, but the LensAlign test was done wide-open at 2.9 feet, with only an inch of depth of field on each side of the focus point. And it was off by nearly an inch.

The picture above wasn’t shot with the bad lens, by the way. It was done with my Tamron 90/2.8 Macro (which, I discovered, falsely identifies itself as a Minolta 100/2.8 Macro!), and the lack of focus was deliberate. It’s a dusty old compact disc that was sitting on a shelf, reflecting the blinds from the nearby window.