principe azul
Ian
+1 on the heavystar/american_eagle hood. Some makes of step-up ring can interfere with the lens when it retracts as you switch the camera off. The hood is no problem.
It makes a great, fast, compact kit just taking the 20mm and no gewgaws - just a spare battery.
Nice to dick around with old M lenses from time to time, as below with a 90mm, manually focusing on squirrels with a 180mm equivalent lens! But the 20mm is a very versatile lens that keeps it a small rig, which is why I bought the lens and camera in the first place.