There’s already been mountains of materials written in the debate between prime lenses and zoom lenses so I won’t spend too much time on that here. I personally do find that the convenience of zooms tends to make me lazier as a photographer whereas primes seem to make me think more about composition and picking the right viewpoints… We used to say that primes offered much better quality than zooms did, but that line has kind of blurred too as pro zooms tend to be very good. But in this post I want to talk about why primes are particularly attractive on the M4/3 system.
First is the obvious: we M4/3 users are blessed with an abundance of excellent, fast, super-small and lightweight primes from Olympus, Panasonic and Pana-Leica. These primes allow us to take maximum advantage of the M4/3 system’s compactness and light weight. We also have some great f/2.8 weather-sealed pro zooms that are very small compared to their full-frame counterparts, but still, they are quite a bit larger and heavier than the primes. With primes you can easily build a complete M4/3 kit with 3 or 4 lenses a body, a flash and some accessories that will all fit into a very small bag and weigh less than 5lbs. If you go with zooms your bag will be about half of the equivalent full-frame kit, but still quite a bit larger than with primes.
But here’s the main reason why I think that primes are particularly useful on an M4/3 system: they allow you to get back those two stops of shallow DOF and noise that you lose to a full-frame system. Let me explain.
Most pros and advanced amateurs that use full-frame DSLRs will mainly use one or more of the so called “holy-trinity” of pro zooms: in my case with my Nikon D700 it was a Nikkor 7-14mm f/2.8, a Nikkor 24-70mm f/2.8 and a Nikkor 70-200 f/2.8. Every one of these lenses is huge and heavy and expensive and they all have a maximum aperture of f/2.8. Now we know that with the 2X “crop” factor of the M4/3 sensors, all-else being equal, we lose about 2 stops of high-ISO noise performance and exactly 2 stops of shallow DOF at a given aperture.
But here’s the deal: if you use fast f/1.4 or even f/1.8 primes you regain most or all of that shallow DOF and high-ISO noise back! Yes, f/1.4 is a full two stops faster than f/2.8 and f/1.8 is about 1.5 stops faster. So by using primes, I can shoot with the same shallow DOF at a given equivalent focal length as I did with my f/2.8 pro zooms on my FF DSLR. I can also shoot with two stops lower ISO, thereby mostly negating the noise advantage as well.
If you add to this the 4-5 stop advantage of the superb Olympus (and Lumix now) in-body stabilization, you can actually shoot at even lower ISO in many circumstances (hence lower noise) than with most DSLRs. So you can enjoy tiny lightweight lenses while losing very little if anything in terms of noise and DOF compared to a FF DSLR.