You asked
Best telephoto lens for the leica sl3 s?
For telephoto on the SL3-S, I'd start with the Leica APO-Vario-Elmarit-SL 90-280mm f/2.8-4. It covers a useful reach in one lens, and it's the one I'd pick if you want a single telephoto that suits most subjects.
If you need more reach for wildlife or sport, the Sigma 300-600mm f/4 DG OS Sports is a serious tool, but it's big and heavy. The Sigma 60-600mm f/4.5-6.3 DG DN OS Sports gives you much more range for less commitment. For a lighter kit, the Panasonic Lumix S Pro 70-200mm f/2.8 OIS is a good everyday pick.
Telephotos get heavy quickly, so check the sensor sizes page before you commit to the longest lens.
Written by Claude from this site's pages.