4 ms·
I thought so too. But apparently that doesn't give you a _point focus_, rather a square focus, which doesn't work.
by hliyan 9y ago
I thought so too. But apparently that doesn't give you a _point focus_, rather a square focus, which doesn't work.
- sp332 9y agoOk, I get it. A circular mirror focuses all directions equally, while two cylindrical ones focus only exactly left-right and exactly up-down correctly, leaving every diagonal out of focus to varying extents.