One of the initial promises of the Four Thirds system was that it would make camera bodies and lenses smaller. This has come true to an extent, but mainly for lenses. There is no denying, for example, that the super compact 9-18mm f/4-5.6 is much smaller and much lighter than an 18-36mm lens of the same nominal aperture range would be for a full-frame system, and the same goes for lenses such as the excellent 12-60mm f/2.8-4. Depth of field is a separate issue, but purely in terms of coverage, Olympus's Four Thirds lenses are generally smaller and more compact than equivalents designed for APS-C or full-frame systems. However, despite their smaller sensors, the top-end Four Thirds DSLRs - the E-1, E-30, E-3 and E-5 - have all been big, heavy, and comparatively expensive for their specification.
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