I got my DK-21M today, and it does fit my D5100 perfectly; no modification required. And in contrast to what others have said, I can see the entire field of the veiwfinder. It sticks out about 1/4 inch further than the factory eyepiece, which is better; gets your face off the monitor screen. And though it is not a huge difference, it is significant enough to appreciate; I will probably never take it off my camera. It is well worth the $20 for a D5100 viewfinder upgrade!!!

After posting last night I went ahead and ordered the DK-21M on the basis of several online user posts of D5100 owners claiming to use it on their cameras. I should get it within a week. I'll let you know whether or not it fits.

The DK-22 does indeed fit on the D5100, but it does give a bit of a hard time at it. A little gentle filing should fix the problem. Unfortunately the DK-17M does NOT fit on the DK-22. I bought the DK-22 anyway, because I may run across something else that may work.

Does the DK-21M actually not fit the D5100? I did notice that Nikon does not list the D5100 as compatible, but I have just read several reviews where people claim to be using it on the D5100,even stating that it does not interfere with the vari-angle monitor. I was just about to order one for mine. Have you actually tried it?

Hi people, does anyone know if there is a magnifying eyepiece available for the D5100? I found a DK-21M listed for several bodies except the D5100, and not surprisingly it didn't fit (why can't Nikon have universal eyepiece attachments?!). I'm wondering if the combination of a DK-22 and a DK-17M may fit, but I'm not sure. I also wonder if I could use a diopter like the DK-20C as a magnifier, but I'm not sure about that either.

I'd like to get a little more magnification of the viewfinder for using it with MF lenses. Thanks for any help.