Another Panasonic lens I tried past summer is again a Leica designed lens, manufactured by Panasonic to Leica standards. Also this lens has been widely tested and reviewed all over the internet. That's why I will again pass any detailed descriptions and concentrate just on how I felt like using it and how my prints look like.
As there was so much written about the lens I was not afraid to try it while working on my Finland project. My style for these images is very straightforward and I shoot mostly at apertures f/2.8 - f/5.6. The sweet spot of every good MFT lens falls into this range. This happens also here. The 15mm lens has its highest optical performance at f/4 and the best range is just what I needed: f/2.8 - f/5.6.
To see the behavior of this lens in the corners and edges of image I did some good old "brick wall" testing. Image center is very good already wide open. Corners are also good enough for me at f/2.8. While the resolution in the corners is not bad wide open, there is another problem. (Click on arrows left/right on image above to see). Everything which is out of focus and close to camera is difficult to process. I did not try other converters but at least in Lightroom any sharpening in out of focus areas looks bad. It makes things difficult as in-focus and out of focus areas may be overlapping in the depth of image like above. The only solution would be manual work and it is time consuming to create believable transitions from soft to sharp when there are various lengths of transitions.
Most of my images are based on depth and details, so in general I avoid anyway shooting at wider apertures than f/2.8.
There were exceptions where selective sharpening is easy. Only then I opened up with Summilux, like here to f/2.2, in order to keep ISO at 200.
Tests have shown this lens to have some distortion. Because of automatic correction there is no need to worry about it. EVF is shows what I get in the end and I can crop exactly how I want it already in the camera. Also other aberrations (like chromatic aberration or vignetting) in images were easy to correct in Lightroom. No problems there either.
A small lens is the more preferable the closer you are to people. This lens is fast and unobtrusive to use. As it now is, Summilux does not give me any actual light gathering (with high quality) or general quality advantages over my most used lens, the M.Zuiko 12-40mm f/2.8 PRO zoom. At aperture range f/2.8 - f/5.6 they are hard to tell apart in prints. The only advantage of Summilux is its smaller size.
I tend to shoot most of the time with sun behind me. Sometimes I shoot against the sun and then I again liked the very good lens hood of Summilux. At 15mm focal length the lens hood of M.Zuiko 12-40mm is as good as useless for shading the front lens from oblique light.
The last two lenses I have written about, Olympus M.Zuiko 40-150mm f/2.8 PRO and Panasonic Leica 42,5mm f/1.2 DG Nocticron, are absolutely great lenses. They belong to the top class of all lenses from all manufacturers. Sadly 15mm Summilux is not alike. Those two lenses can be used wide open without any worries about quality. It is always there. Summilux is good wide open if your subject matter or shooting style needs no great corners. Closed down to previously mentioned aperture range I would not hesitate using it, only it is not better than what I already have in a zoom lens. I did not bother doing any direct comparison with M.Zuiko 17mm f/1.8 but I would expect Summilux to be slightly better when shooting a test target. Only I have never seen the same odd behavior in out of focus corners in images from the 17mm lens. That is with images processed in Lightroom, in my way, remember!
What Micro Four thirds is missing is a truly great "35mm lens". While I liked the angle of view of Summilux, I really don't mind if that truly great lens would be 15 or 16 or 17mm. I also don´t mind if it is f/2 or whatever faster than that. By now I even wouldn't mind if it would have a similar price tag as Nocticron. The wait has been long enough. Just somebody, make it! Panasonic, Olympus, Sigma, Zeiss, Tamron... who ever. I don´t care.