07 November 2011

test every lens (no matter how many times you own a copy)!

Sure, I admit it: this is at least my third Pentax 18-55 lens. Each time the purchase, and the sale, made sense within its context. This time I own a WR camera with no WR lens.. so the DA 18-55WR makes plenty of sense.
Each time I change lenses I enter a column in my Excel 'data base', so in many cases I've been able to copy a column from the dead file to the live one. And each time the parameters change a smidge, so I test where the minimum f/ratio changes through the focal range, and take a quick shot of a ruler to count the mm and determine the close-focus ability.

In this case I picked a real close-focus winner among the many excellent 18-55s: this is very close to .4x (I see 62mm at close focus, so sensor size of 24/62 yields 0.39x). The specs say .34 and my previous were closer to that value. I did lose slightly on the f/ratio, but if you can tell the change at 35mm instead of 40mm you're better at it (and more concerned about it) than I.
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Later tests against the DA 50-200 are less glowing, as the 50-200 at 50 bests the 18-55 at 55 when both are f/5.6 aperture. Also curious is that the FL values aren't quite aligned - so do I have a 55-200 or an 18-50? No big deal, just a curiosity.