Everyone's different, but my experience tallies with sokoloff's. With the right technique it's no problem to solder 0603 with the naked eye. 0402 is possible bu

Everyone's different, but my experience tallies with sokoloff's. With the right technique it's no problem to solder 0603 with the naked eye. 0402 is possible but very fiddly. 0201 is really pushing it. A microscope is a useful aid, especially if you're longsighted.