The Nikon D3100 is 6.4 mm narrower, 2.5 mm taller, 11.9 mm deeper and 8 g heavier than the Olympus OM-D E-M1.
| Olympus OM-D E-M1 | Nikon D3100 | |
|---|---|---|
| Size (W × H × D) | 130.4 × 93.5 × 63.1 mm | 124 × 96 × 75 mm |
| Weight | 497 g | 505 g |
| Lens | Micro Four Thirds | Nikon F |
| Sensor | Four Thirds | — |
| Announced | 2013 | 2010 |