Comparing the camera sizes
Traditionally, we expect professional-level and full-frame cameras to be larger and heavier than those with APS-C or smaller-format sensors aimed at enthusiasts.
This is borne out by the differences between the Nikon D300S (147x114x74mm and 825g) and cameras further up the Nikon DSLR line such as the D700 (147x123x77mm and 995g) and D3S (159.5x157x87.5mm and 1,240g).
Similarly, the Sony Alpha 850 is considerably larger (156.3×116.9×81.9mm) and heavier (850g) than the Alpha 550 (137x104x84mm and 599g).
However, there are only a few millimetres difference between the Canon EOS 7D (148.2×110.7×73.5mm) and EOS 5D Mark II (152×113.5x75mm) and, at 820g, the EOS 7D is 10g heavier than its full-frame counterpart.
It is worth bearing in mind that full-frame lenses have to cover a larger imaging circle than their APS-C-format equivalents, so they are generally larger and heavier. Consequently, it may not be the cameras that determine the difference in weight of a camera bag, but the optics used with them.
| Camera | Dimensions | Weight |
| Canon EOS 7D | 148.2×110.7×73.5mm | 820g |
| Canon EOS 5D Mark II | 152×113.5x75mm | 810g |
| Nikon D300S | 147x114x74mm | 825g |
| Nikon D700 | 147x123x77mm | 995g |
| Nikon D3S | 159.5x157x87.5mm | 1,240g |
| Sony Alpha 550 | 137x104x84mm | 599g |
| Sony Alpha 850 | 156.3×116.9×81.9mm | 850g |
