Another example of the 17 lenses ability to produce very practical and nice bokeh. At F2 it shows obvious drop off of depth of field, but the left and right sides of the image look pleasantly coherent. The good central sharpness, enhanced by good micro contrast, allow the front of the rail to stand out well against the immediate background of the wall and the areas further away are well and logically rendered. Notice how your eye can stray to other parts of the image where you expect sharpness and may feel you find it (back edge of the wall front), but when you look back to the hand rail holder, the sharpness jumps at you a bit. this allows the image to transition effortlessly from the point of best focus, to other areas of the image without calling out the focus/sharpness difference. In other words, you can tell a story with the whole image area without worrying about micro differences in focus point accuracy, but also prioritise the prime focal point slightly over the supporting elements.
A focus miss is a miss, but how the lens renders those misses is part of it's character and practical benefit.
In practical terms, I found the Panasonic 20mm lacking (on EM5's) because it lagged in auto and manual focus speed (meaning in real terms accuracy) and it's bokeh had the more in vogue fast drop-off of focus, showing misses in all of their glory. I would not hesitate to shoot with the 17mm at f1.8-2.8 if needs must, knowing that the lens is very forgiving in it's depth of field transition. The 20mm lens would be used in a more considered way, applying wider apertures only to highlight sharp to blurred areas of an image. it would also require a lot more accuracy and smaller apertures when applying fixed "zone" focusing like below. In my kit, the 25mm f1.8 fills the role of the preferred 20mm focal length as I feel it does what that lens does only better, being a little longer. It is not that I like 25mm more than 20mm (I like 20-40mm equiv the most of all focal lengths), but I like the 25mm's perspective better in the way the two lenses render and the 17mm at what it does.
By comparison, the 12-40 zoom with it's "portrait" bokeh drops sharpness away faster and more dramatically and provides more "blobby" smoothness, considered by many to be the bokeh ideal. I will do better/closer comparison images at some point.
The 12-40 would have made the above (hand rail) image more fashionably sharp/soft, taking away some of the story telling ability the 17mm provides.