Today I tried the 90mm ,45 mm and 35mm on the GF1.
90mm shines. It really does. Probably the best 90mm for the GF1. I had tried my Leica 90mm, but I like this one better (on GF1).
45mm is the best also in the 40-50mm range lenses that I have tried on the GF1.
35mm is better than my Summilux 35/1.4. Actually the Summilux is excellent on the Leica M8. But in GF1, the Contax 35/2, which is a decent lens only on the Contax G2, is superior to the Leica version on GF1. Whereas IMO, the Leica 35/2 sucks on the GF1.
About adaptors in general:
Contax to GF1 adapter (Fotodiox in my case) has some stiff areas while focusing, but gets better as you use the adapter. It still is a challange to use it.
I tried M42 lenses, Leica lenses, Nikon lenses and finally the Contax lenses on GF1. I think, unless you are a hobbyist trying to experiment, using adapters is stupid especially in the wide angle area. The camera has a 2X multiplier, and that makes all old WA lenses unusable as WA. 28mm becomes 56 mm. So what's the deal then?
I have Oly 17mm and Panasonic 20mm lenses. None of the old WA lenses can beat them. So forget about your old MF WA lenses, which are generally like 28/2.8, which you don't need in the GF1. The 20/1.7 Panasonic makes great photos, and with AF. It's also small in size. Oly 17/2.8 is also great if you need 35mm.
Because of design considerations of the film era, many excellent lenses of their times do not perform well on the GF1. I tried a few with great expectations, but the results were very unsatisfactory. (Nikkor 50/1.2, Summicron 34/2, and the list continues.). I didn't even bother to try the Contax 28mm, because even after shaving the extensions, I suspect that it will not be better than any of my Panasonic lenses anyway, and it will be a 56mm lens. Who needs that?
Therefore, unless you want to play with all your existing lenses, you don't need to buy the converters at all. Only in the 90mm case, the existing lens line up of Panasonic has no alternative with a F2 or 2.8, and therefore, with their excellent performance on the GF1, I can recommend the Contax 90/2.8 or the Leica 90/2 lenses.
On the WA side, you are better off by buying the expensive Panasonic (or for Olympus cameras, the Oly version) 7-14mm lens. These lenses are excellent..
There are no 7-14mm lenses from the past anyway that will give you this range even with an adapter.
To summarize, unless you need excellent tele lenses, don't waste your money on adapters. Having said that, I'm still in the precess of buying all existing adapters, because I 'm a hobbyist with a lens (and camera) collection, that I want to play with.
Have a good weekend,
Seyhun