Landscape Photography: 4/3rds VS APS-C

As with most things, lenses matter an awful lot.

Four Thirds offers an excellent cheap wide zoom, the 9-18 f/4-5.6; I have one and find the review on dpreview (back when they were in the business of actually reviewing equipment rather than telling me what someone did with a cellphone camera last week) to be quite accurate.

There are a couple of other lenses you might use: the 12-60mm f/2.8-4, which doesn't go as wide but goes far longer, is very sharp, and is weathersealed; the 11-22mm f/2.8-3.5, which is weathersealed and faster than the 9-18, and the 7-14mm f/4, which is a premium lens at a premium price that is apparently very good.

The drawback with 4/3 is the low resolution and shadow noise of the sensor available in current bodies. If 12MP with the image quality of the E-5 sensor (or E-30 sensor, or whatever) is good enough for you, then you'll have no problems; I shoot landscapes quite happily with my E-30.

If you mean "micro 4/3" (the little mirrorless cameras made by Olympus and Panasonic) instead of "4/3" (the "real SLR's" made mostly by Olympus), your concerns are even less of an issue, since there is a much better sensor available, the 16MP sensor in the E-M5 and other models. You can use all the lenses mentioned above, and for landscapes the slower focus won't be an issue. There is also an excellent 12mm f/2 and 7-14 f/4 available in native Micro Four Thirds mount (along with some other lenses that cover the traditional landscape range, some better than others).

Hope this helps.