We where on the Rhein at Oestrich, going to Worms, together with the ship in the picture. We always start early so we caught a nice Sunrise and I saw this picture starting to come together.

I switched to my Elmarit 2.8/135mm and attached the Visoflex EVF. 
For those outside the Leica World, the Visoflex is an Electronic View Finder (EVF) for the Leica M camera. An M has a very basic viewfinder (although technically very complicated) and this viewfinder is not very suitable for any optics longer than ca 90mm. The Elmarit I have is even equipped with a special optical device that will enhance the regular viewfinder, but even then it is far from ideal. 

With the EVF we suddenly have a mirrorless camera that enables you to view the image directly from the camera sensor, allowing you to look through your lens. Ideal for longer lenses such as this one.

This picture was taken with a Novoflex 5.6/400mm lens, impossible on a regular M Leica.
Leica did manufacture a 'reflex housing' for the Leica M camera, the 'real' Visoflex. I have  the latest one, version III. You can attach this mirror housing in front of your camera, turning it into a Reflex camera (as opposed to a Rangefinder). Designed for film Leica's in the late 50's it even works on today's M10, although the EVF Visoflex is a lot easier to work with in real life, some progress was made indeed.

Only problem, this 400mm lens (the Leica adapter, actually) was designed for the Visoflex III, with a different lens-to-film/sensor distance then the naked M10 can deliver. In short, it wants the old Visoflex mirror box in order to be able to focus on infinite.
But even with that cumbersome outfit the M10 will work and is capable of nice results.

This one was shot at Terneuzen, ISO 3200, 5.6 - 1/60s, Monopod.