In addition to a weather-sealed body, the D7100 offers some nice design improvements over the D7000.
Lori Grunin
I've been reviewing hardware and software, devising testing methodology and handed out buying advice for what seems like forever; I'm currently absorbed by computers and gaming hardware, but previously spent many years concentrating on cameras. I've also volunteered with a cat rescue for over 15 years doing adoptions, designing marketing materials, managing volunteers and, of course, photographing cats.
While there are a few control layout changes -- some of which I like, others of which I don't -- overall the D7100 has the same look and feel as the D7000. However, the new model is of sturdier construction; it's composed of magnesium alloy and weather-sealed much like the D300s.
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Top
There are four major changes here. Yay for the lock button on the mode dial, though I don't like it in the center. And there's now a built-in stereo microphone. Plus, Nikon's replaced the annoying dangly strap mounts with fixed rotating ones. But the movie record button is one of those too-small, poorly placed controls that's unfortunately become quite popular.
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Bigger grip
The grip on the D7100 is noticeably deeper -- even though the body itself is the same depth -- and feels a little more comfortable.
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Grip
Here you can see the more curved shape of the grip, which adds to its increased comfort. The camera retains the dual SD card slots.
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Back grip
That rubberized portion down the right side is also new, an expansion of the thumb grip from the D7000.
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Back layout
The real changes are on the back. The lock button is now integrated with the navigation control -- which I like -- but the record button has been moved to the top, where I don't like it. I liked the Live View toggle switch on the D7000, but the D7100 uses a more typical control. The i button on the bottom left is new and adds quick-menu functionality.