50mm f/1.4? We spit on your 50mm f/1.4!!

[Westside guy]

The short answer is that the diameter of the lens mount and minimum distance between the rear element and the focal plane (due to the mirror box) makes f/1 the maximum aperture for full-frame coverage on any current SLR mount. There is a real physical limitation here. (I guess covering an APS-sized sensor at <f/1.0 might be possible, though.)

It's the maximum aperture for full-frame coverage focussed at infinity, I believe.

 

[vga4life]

It's the maximum aperture for full-frame coverage focussed at infinity, I believe.

A hat-tip to you, sir. That's quite right.

 

[Westside guy]

A hat-tip to you, sir. That's quite right.

Okay, I have to admit this - after I typed that, I started to think maybe I was remembering wrong... so I went scrambling to check it.

 

[pit29]

I was wondering the same... What does F<1 conceptually mean if F=1 is maximum light - to my understanding that meant that it cannot possibly capture more?

So, are F<1 only mathematical constructs, or is this also associated with an idea? And if so, what'd be the (theoretical) limit? How would an F=.1 lens look like??