Which lens did you regret buying and why?
My regrets:
Canon 70-200mm f2.8 IS -- I bought this one due to the hype. I thought it would be the perfect portrait lens for me. I replaced it with two primes : Canon 135mm f2 and Sigma 85mm f1.4 because they are lighter, faster, and easier to calibrate. I would get the 200mm f2 too, but I have to eat.
Canon 100mm f2.8 IS Macro -- I got this one to pull double duty: part-time macro and part-time portrait. I replaced it with the 180mm f3.5 Macro which is a better dedicated macro lens. And for portraits I prefer primes that can open up to f2 at least for more background blur, hence 135mm f2.

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