I just spent a long weekend at a music festival with the new Lumix 12-35mm f2.8 Aspheric lens attached to my Panasonic DMC-G3. So what do I think? I'm conflicted to tell the truth.
First off - it was very nice to not have to change lenses much. The lens worked very well for shots of the crowd, dancers, vendors, and those types of things. It also did fine with wide shots of the bands. But, let's talk about that for a second. In shooting a full-stage image of a performing band, I needed to stop down at least a little - f4 at least, more likely f5.6. In daylight performances, not an issue at all. After dark, that required a little flash. But the real point is, if I'm using the lens in this way, why does it matter that it has a maximum aperture of f2.8? The answer is, it doesn't matter at all. I could have done just as well with my Lumix 14-140mm f4-5.8 lens. In fact, I would have had a much more useful focal length range. Yes, it's true that I'd lose the 24mm full frame equivalent field of view of the wide end, but that's not common territory for me anyway.
And that brings up another point. As I mentioned previously, the 12-35mm is just a little short of being a great portrait lens.
(Click Here) for my intial thoughts on the 12-35mm for candid portraits.
Now portraits are where the f2.8 can become important. But, at 35mm maximum focal length, f2.8 just doesn't quite do it.
Finally, I've become spoiled by my primes. At "normal" focal length, my Lumix 20mm f1.7 and Pana-Leica Summilux 25mm f1.4 lenses are so fast, f2.8 seems a little slow (in light gathering capability). I'm about to become even more spoiled, when my Olympus 75mm f1.8 prime shows up.
So, as you can see, I'm pretty far along in talking myself into returning the 12-35mm f2.8.
I think I would rather carry two camera bodies, and a couple of extra lenses, rather than accept these tradeoffs. I though that the 12-35mm may be important for event and travel photography for me. This weekend told me that I would be happier with primes at events. For travel, the 14-140mm f4-5.6 is still a great option for well-lit scenes. It has enormous focal length range, too.
Just for balance, you may be interested in reading a post on ePhotoZine about the joys of zoom lenses.
(Click Here) to read one author's experience of reducing his Nikon DSLR kit size with a super-zoom (Nikkor 28-300mm).
Just imagine the benefit this author would get from Micro 4/3 gear. Weight becomes negligible with a single body, single zoom approach.