10-19-2013, 08:21 AM
A Sigma 150mm f/2.8 Macro?
On which camera do you use it?
Just a guess: You are using the lens in macromode (where the effective
aperture begins to drop down) and the lens is reporting its real maximum
aperture (at the focus distance in use) to the camera.
To find out if this is the case, make your tests with fokus set to infinity.
Then you should be able to open up to f/2.8.
Rainer
On which camera do you use it?
Just a guess: You are using the lens in macromode (where the effective
aperture begins to drop down) and the lens is reporting its real maximum
aperture (at the focus distance in use) to the camera.
To find out if this is the case, make your tests with fokus set to infinity.
Then you should be able to open up to f/2.8.
Rainer