The D5200 uses a cheaper ‘pentamirror’ design which covers 95% of the image area the sensor will capture, but the D7100 has a more expensive and traditional ‘pentaprism’ design which provides a better image and covers a full 100% of the image area.
You may not notice the difference if you use either camera individually, but you will if you put them side by side.
The D5200 has a shutter speed range of 1/4000 sec to 30 sec, while the D7100 goes from 1/8000 sec to 30 sec. It has a small advantage, then, but the situations where you’ll actually need or want to shoot at 1/8000 sec will be pretty rare.
More usefully, the Nikon D7100 has a flash sync speed of 1/250 sec, whereas on the D5200 it’s 1/200 sec. This gives the D7100 a slight advantage for fill-flash photography in bright daylight.
The D5200 can shoot continuously at 5 frames per second (fps), which is pretty good for an amateur camera, especially one with such high resolution, but the Nikon D7100 can shoot at 6fps – or 7fps in its 1.3x ‘crop mode’. This gives it a modest but significant advantage for sports and action photography.
The D7100 takes an optional battery grip (the new MB-D15), but the D5200 does not. This gives the D7100 an additional advantage for continuous shooting – the maximum frame rate remains the same, but with an EN-EL15 battery fitted in the grip, it can take up to 1,900 shots between charges.
The MB-D15 can also take 6 AA-size batteries. Apart from offering improved battery life, the grip makes the camera easier to hold and has an additional shutter release button and command dials positioned specifically for vertical shooting.
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