Today I quickly tried the Voigtlander 17.5mm f0.95 and the Panasonic/Leica 15mm f1.7.
1. The Voigtnlander
- very heavy, but feeling as sturdy as a piece of concrete. I switched from Nikon D3s to m43 mainly due to weight, so this is a decisive factor
- manually focusing with it is relatively fast for someone like me who has lost their muscle memory for this task. The focus peaking on the GX7 works quite reliably even when I try to shoot as if I'm in a hurry - like I often am during a wedding. Indeed, I still miss focus but with practice I can become more proficient.
- the aperture ring is so loose that I rotate it even by holding it. I sometimes found myself shooting at f2 without ever feeling that I've changed aperture. That's also because there are no steps on the ring and it rotates smoothly.
- the lens' sharpness is ok at wide open - the way I'd shoot it often.
2. The Panasonic/Leica 15mm f1.7
- it's very tiny and super light. It's all plastic and for weight's sake this is a good thing. I wish my 42.5mm f1.2 Nocticron was plastic so it wouldn't be so heavy for a m43 lens.
- the build quality is good. Everything feels tight.
- the aperture ring is tight and clicks noticeably. I like it.
- the lens, compared to the m.Zuiko 17mm f1.8, strikes me as very noticeably sharper. Viewing its images at 100% remains a pleasure. With the m.Zuiko I'm always reaching for the sharpness slider.
- AF feels significantly faster
My conclusion is that I'm going to buy the Panasonic/Leica 15mm f1.7 because it provides a good balance between low weight, excellent sharpness on par with my other great lenses, it's half the price of the Voigthlander, it provides me with the fastest AF from the three. It also is reasonably small to put it in my pocket with my E-PL5.
I'm happy that I found a worthwhile contender as a ~35mm equiv. lens.
What's left for me to decide is whether to get rid of my m.Zuiko 12mm f2 or to keep it. If I keep it I'll always be wondering whether to put it on instead of the 15mm f1.7.