Get Leica 90mm f/2.4 Summarit-M at B&H Photo
But the Leica 90mm f/2.4 Summarit-M does have one weakness (as with most Leica M lenses): veiling flare issues, even from things as common as an overcast sky.
In Guide to Leica, this eight-frame series shows how veiling flare develops or is minimized by small changes in angle to a light source, and how including the light source shows much less flare than having the source just out of the frame.
The series is typical of most Leica M lenses as well as other brands, so it has general value in understanding how flare flares up.
James K writes:
The Leica tele lenses and even some 50mm lenses have always had flare issues. As you have illustrated it does not take too much to create a significant amount of flare. Sharp shooters in a small package. A long lens hood with the front masked exclude as much unwanted light as possible is the way to go with Leitz optics. Nikon has always had good flare control.
DIGLLOYD: The advice to mask off the front of the hood is good.
As for Nikon, flare control can be excellent, or it can be deeply troubled by the same issue as shown above.