QUOTE(D800E @ May 29 2015, 03:24 PM)
why 105 micro kenot reach f2.8?
Only when doing macro. The loss of aperture at macro distances is how it is for internal focus lenses. You don't shoot f/2.8 for macro anyways. For normal shooting, the lens works fine at f/2.8.
QUOTE(mingyuyu @ May 29 2015, 05:22 PM)
not say kenot, but only at further focus distance. it's a nature of most macro lens, they tend to close down the aperture automatically as you focus closer and closer. something to do with the optical design i guess.
Errr... if not wrong the Canon EF 100mm IS f/2.8L does 1:1 at f/2.8. Paiseh.
QUOTE(LegendLee @ May 30 2015, 12:54 PM)
At 1:1 ratio, fstop is about f/5.6
It's actually about f/4.8. Oh, VR also does not work especially at 1:1 macro work. Shake is too amplified at this magnification to be compensated by the VR.