Wonderful lens for extreme macro work. Crystal clear wide open, a bit blurry wide open, but that's the case with almost all dedicated macro lenses. The working distance is stable, about the same at 2.5x and 5x magnification. Can also be used with an extension tube kit for even greater magnification. When used with an APS-C sensor, this results in around 8.5x magnification (at the sensor), which translates to around 40x magnification for an 18MP 600dpi image. Nothing for the average user, probably not the best lens for photographing insects in the field. I use it on a copy stand with StackShot.
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