Hi everyone. While this lens can be great and sharp on some images, I sometimes get soft pictures with others using my D5100. Hoping others can chime in or offer advice. I know that with f stops between 1.8 and 2.8 the plane of focus is very small. So if I'm shooting 2 kids and one kid is behind the other, I expect one to be softer than the other. So, I try to keep my f stop lower like 5.6 or 6.3 or go lower if I'm only shooting one kid. I recently took pics at 2.8 and 5.6 and both kids' faces were soft. For the f2.8 shot, they were nearly on the same plane and my shutter speed was ok I think (1/200). I did focus somewhere right between them if not on one of their eyes (from what I recall). As you see, neither of their faces are sharp. For the f5.6 shot, my shutter speed was slower (1/125) but I don't think that was the issue. I've gotten similar results with faster speeds. The kids were on different planes but I figured f5.6 would be ok. Again, neither face was sharp. I believe I focused on my son's face and even his is not in focus. I'm concerned about a focusing issue with my lens...it's still under warranty until December so I gotta act soon if I want to send it back. Or maybe it's operator error. Both pictures are right out of camera with only some minor sharpening and lens correction applied by Lightroom on import. Thanks!