Union Station

I dodged a big bullet this morning, only losing the filter on my expensive 17-55mm f/2.8 lens when it fell to the floor with a heart-stopping THUD, the camera bag strap caught by a piece of furniture. There were no scratches on the lens itself and no apparent motor damage. It was at Nikon Repair just six months ago! The damage is cosmetic — a few prominent scratches on the metal around the lens — and I have to dig up the filter receipt to claim a replacement on the insurance. (Sigh of relief that I bought replacement insurance on this filter, because this is the second one I’ve busted.)

Having dodged the aforementioned bullet, I was in no mood to invite another one while wandering around Front Street with a naked, filter-less lens. But I also wanted to confirm the focus mechanisms were still working (that was the main reason I had to repair it last year — the lens was scratched minimally but nine months after it hit the kitchen floor at The Brides’ Project it wasn’t focusing anymore). So I shot off a few photos at different focal lengths to test the lens.

As much as I love this lens, I have come to accept its distortion at the wide end (17mm, or about the equivalent of 26mm on this DX camera body). Sometimes it bugs me, but I’ve learned to position myself properly so the bits I want straight are not in the area with the worst distortion (that being the short sides of the frame). The lenses are round, so how come the photos are in rectangles?

These two photos below are actually the same photo. The top one is how the photo looks without lens correction, what my camera’s sensor views through the lens at its widest. The bottom photo has lens correction applied to make the vertical lines look vertical in the photo. As you can see, it now distorts the size of the sculpture to compensate for the horizontal “stretching” of the top half of the photo to line up with the bottom. It’s the same problem that happens with the Mercator projection of the world: the world is round and a map is flat, which forces a distortion of the relative sizes of the countries.

without lens correction (what my camera sees)

with lens correction (straightening the buildings)

(All this distortion is why I would probably not buy a fish-eye lens. It may be fine for the occasional photo — say, with very large groups of people — but not for regular use.) It’s interesting to think that neither of these photos are accurate to what we can see with our own eyes, which are infinitely more sophisticated than any camera manufactured today.

Brookfield Place