I've been using a 1950's era 50mm f1.8 Canon Serenar on my Leica since 1999 or so and lately I've been worried that I'm not getting as much out of my camera as I might be and was luckily able to test a mid 1990's pre-asph Leica Summilux side by side with the Serenar.
There's definitely a difference wide open in the bokeh -- the Summilux is a lot smoother. It's also half a stop brighter and the color is a bit different. And the Summilux focuses closer, which is a distinct advantage, though it's also significantly larger and heavier.
In the 100% crop it seems a bit sharper but at this aperture it could also be a focusing variation as well.
My ultimate conclusion is that the Summilux, while nice, isn't $1,200 nicer than the Serenar.
I much prefer the first image, but that might have more to do with composition. Do you find that 50mm lens work best for portraits? Have you ever used longer lens for portrait work? How long would you go?
If I was shooting portraits for money, I'd use the Nikon d800 and the 85 f1.8 which I've dubbed "the rock star lens" because everybody looks like a rock star when shot with it. With the Leica, the 50mm is the best (imho) Leica makes a 75mm 1.4 and a 50mm .95 both of which are notoriously difficult to focus on a Leica M. (More about the 85 1.8 here: http://photographers.livejournal.com/17884473.html) I've also used a 300 2.8 as a portrait lens, which is really nice, but cumbersome.
Very cool. I personally think longer lens, if used accordingly, can produce some excellent portraits. My main beef is the excessive use of wide lens for portraiture, which more often than not results is distorting and elongating the subject's features.