Rokkorfan
21st of March 2005 (Mon), 04:17
Hi all,
This is to a fairly select group I expect, but here goes - I got a 2x II converter today and tried it on my 1D MkII and 300mm f/2.8 IS. Fantastic results, really impressive sharpness, positive fast focusing and maybe 1 pixel of CA (only on high contrast edges and barely detectable at 100%.....suffice it to say I am thrilled.
However, when I stacked the 1.4 and 2x converters I got a surprise. I was expecting the camera to focus well, given the centre focus point on the 1D MkII is good to f/8. Well first of all, the camera still read an aperture of f/5.6, not f/8 as I expected, and the camera really just would not focus - kept hunting, and only focused when I focused by hand and it touched up the focus, or when I sort of jiggled the shutter release, and it (sometimes) would get focus then. I presume this was because it was close to correctly focused when I released the shutter button, so it could "touch up" the focus when re-pressed.
Now I know we are talking extremes here, and that the camera and lens were probably not designed to work with stacked converters, but is this usual behaviour? I note that individually with both the 1.4x and 2x converter the lens will focus correctly and the camera will report the correct (ie. multiplied) aperture.
Note: I switched to centre focus point only for this test, my subject matter was contrasty with horizontal and vertical lines, and the test was shot in sufficient light.
Best regards,
Antony
This is to a fairly select group I expect, but here goes - I got a 2x II converter today and tried it on my 1D MkII and 300mm f/2.8 IS. Fantastic results, really impressive sharpness, positive fast focusing and maybe 1 pixel of CA (only on high contrast edges and barely detectable at 100%.....suffice it to say I am thrilled.
However, when I stacked the 1.4 and 2x converters I got a surprise. I was expecting the camera to focus well, given the centre focus point on the 1D MkII is good to f/8. Well first of all, the camera still read an aperture of f/5.6, not f/8 as I expected, and the camera really just would not focus - kept hunting, and only focused when I focused by hand and it touched up the focus, or when I sort of jiggled the shutter release, and it (sometimes) would get focus then. I presume this was because it was close to correctly focused when I released the shutter button, so it could "touch up" the focus when re-pressed.
Now I know we are talking extremes here, and that the camera and lens were probably not designed to work with stacked converters, but is this usual behaviour? I note that individually with both the 1.4x and 2x converter the lens will focus correctly and the camera will report the correct (ie. multiplied) aperture.
Note: I switched to centre focus point only for this test, my subject matter was contrasty with horizontal and vertical lines, and the test was shot in sufficient light.
Best regards,
Antony