JC Optics 400mm f/8 MFT: Ultra-Simple Tele for Curious Hands

A 3-element, 400mm f/8 manual focus lens covers a lot of mount options but very few use cases. At f/8 you're already at minimum aperture on most bodies in bright light, autofocus shooters are out entirely, and a 3-element optical formula isn't winning any resolving tests against a modern tele. The 1m minimum focus distance is genuinely interesting for close-range compressed shots, and all-metal construction with adjustable focus damping suggests it's built properly. But this is a toy for optical experimenters and lo-fi tele fans, not something you'd trust on a paid job. File it next to cheap cinema lenses and pinhole adapters. Fun if that's your thing, safely ignorable if it isn't.