My only hiccup when using the new 75mm lens, was that it sometimes slowed down a little when focusing.

Thought I should check this out further, and see how the lens performed on an Olympus body; so I borrowed Nik’s EM-5 for a few hours. This also provided the opportunity for a camera porn shot; don’t they look lovely together?:

Once I had finished ogling, I set about pointing the lens at things with both cameras, with the following conclusions:

1. I thought that maybe the lens would work differently if attached to the same make of body, but the Olympus EM-5 does not focus the lens faster than the Panasonic GX1. In fact, the GX1 seemed to be fractionally speedier; but as I have no idea how Nik has set up his focusing rules on the EM-5; we’ll call it a draw.

2. In good light, both cameras acquire focus at a speed which can be described as “instantaneous”, even though it cannot be. When used with modern M43 lenses, these most recent bodies from Olympus and Panasonic claim to be the fastest focusing cameras on the planet and I wouldn’t disagree.

3. In low light, “almost instantaneous” would be the appropriate phrase, unless you are moving from focusing on something close to something distant, or vice versa, in which case there is a slight pause as the lens moves to the new position for focusing. Is it slow enough to be an irritant? No, but it is noticeable and is not present if you use, for example, the 25mm Summilux.

I initially assumed the issue was to do with having to move a substantial piece of glass in the lens; but then this would be evident whatever the light level; so it must be something else.

Not something that I am going to worry about. Unlike many cameras I have used, the GX1 has an astonishing ability to lock focus in almost complete darkness; and if I have to wait a fraction of a second with the 75mm sometimes, it is not a problem. Also, unlike many cameras (are you listening Canon and Nikon?), Olympus and Panasonic do provide firmware updates for individual lenses to improve performance; so maybe the 75mm will get a boost at some point.

Postscript:
DPreview have just published a little video comparing focus/shoot times between a Canon and a Panasonic G5. The Canon focus system is the same as that implemented in the wanky new EOS-M. The G5 system is probably a little slower than the GX1 or EM-5; but it totally destroys the Canon.