3 ms·
It's an American think afaict. I still don't quite get how it works, just that it has something to do with feet.
by lucian1900 14y ago
It's an American think afaict. I still don't quite get how it works, just that it has something to do with feet.
- taejo 14y agoIt's a ratio of distances -- the benchmark distance is 20 feet but that's non-essential. 20/10 means you can see the same level of detail at 20 feet that somebody with "normal" vision can see at 10 feet.
- lucian1900 14y agoThat seems problematic, how is normal vision defined? With dioptres, the definition is very clear and based on optical properties of the eye.