Noctilux
The Noctilux at f/0.95 delivers just enough light to focus with the EVF on the Leica M Typ 240 when I can hardly see. This is not possible with the rangefinder (too dark for naked eye).

Leica M240 + Leica 50mm f/0.95 Noctilux-M ASPH, f/0.95 @ 45 seconds

Leica M240 + Leica 50mm f/0.95 Noctilux-M ASPH, f/0.95 @ 24 seconds

Leica M240 + Leica 50mm f/0.95 Noctilux-M ASPH, f/0.95 @ 24 seconds