Well, I received a very unexpected bonus a couple of weeks ago and my wife suggested I spend it on something I would not normally buy. I decided on a new Canon 70-200 f2.8 L USM. While I was looking, I stumbled across some Kenko extension tubes, used but in great shape at a very good price.
I got a chance to play with the tubes this afternoon. First, the obligatory cat (Francis) photo with the 70-200 @198mm, f2.8 1/250:
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Next are photos from the yard taken with one or more extension tubes with a Canon 100mm f1.8:
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It's been dreary and raining, so it was nice to get out in the yard and play. Nothing special.