Yes, it means that i'll be diffraction-limited, even if the lens is F/1.0. It'll be diffraction-limited for red light around F/0.9. It's possible to make lenses

Yes, it means that i'll be diffraction-limited, even if the lens is F/1.0. It'll be diffraction-limited for red light around F/0.9. It's possible to make lenses that open, but hard. That's why camera phone lenses are so funky.