I'm going on safari in South Africa and wondering if a micro 4/3 camera will be able to handle the low light conditions (since safaris are at dawn and dusk). Specifically, I'm looking at the Panasonic G3 (with the 100-300mm lens). Has anyone taken this camera (or similar), and if so, how did it handle the low light conditions? Would a DSLR be much better?
It really comes down to your expectations and priorities. In my case I moved from a DSLR to a G3 because I got tired of the size and weight of the former and love the form factor and discretion of the smaller camera. In terms of high ISO performance (which is what you need for the safari) - my DSLR was a 2006 model - great at low ISO but nasty at 400. My G3 gives me beautiful results up to 3200 although some detail is sacrificed of course due to noise reduction. Now, if you put the G3 side by side with a DSLR, you will probably see slightly better results due to greater dynamic range and so forth, but in my case it is not enough to make me want to go back to bulk. So bottom line: if size doesn't bother you and are really picky about image quality then go with a DSLR, but if you prefer something smaller, lighter and more discreet and almost on par in IQ then go with the G3.
Every camera has a limit and so does the Panasonic G3. What's more is that you will encounter that limit on various occasions and quite possibly on safari.
A camera with a larger sensor will perform better in low light. That means DSLRs and even SLDs with APS-C sized sensors, followed by full-frame DSLRs. The real question is how much is this worth to you? Getting one of those cameras is more costs, bulkier and heavier.
The 100-300mm lens you mention is equivalent to a 200-600mm on a full-frame DSLRs, so you are getting a lot of reach in a relatively small size. You are also getting a reasonable F/5.6 aperture at the long end which is quite costly for a 600mm lens. If you go halfway to an APS-C camera you can use a bright F/2.8 400mm lens which will give you two stops additional light and lets you use higher shutter-speeds too. This would already be better not including the advantage of having a larger sensor.
Depends on what you mean by "handle low-light conditions."
The G3's high iso performance is good. I've found ISO 3200 usable, though not flawlessly so. On those grounds, you have nothing much to worry about, unless you plan on shooting in serious full-on darkness requiring iso 6400 or higher.
However, the G3's autofocus system in low light--that's another matter. I've had it hunt intolerably in low light and missed every fast-action opportunity I had for stage shooting. And the autofocus speed with the supertelephoto lenses is a third matter yet.
If I'm going to the zoo, I bring my G3 and 45-200 OIS. If I'm going out to shoot birds or mule deer in the back cayons, I grab my Canon 50D and 400/5.6L. The high-iso performance is roughly the same between the two. But I can rely on the speed of AF lock on the Canon dSLR; I can't on the Panasonic μ4/3 gear. Partly it's the body, partly it's the lens. The EM-1 and the upcoming Olympus 300/4 lens might change the game, but at this point, dSLRs (and their lenses) are still better tools for fast-action supertelephoto photography.
If you're shooting elephants at a waterhole, the G3+100-300 will probably work just fine. If you're trying to shoot a cheetah running through the grass, or an eagle in flight, maybe not.