John Landolfi wrote: No. You lose aperture with a converter because you are putting extra glass between the light and the sensor. The crop sensor just gives you a smaller, central portion of the image a full crop would produce, so will have no effect on aperture, all else being equal. The converter may also raise some sharpness isues, which is why choosing the best you can afford is recommended. Not much sense in putting the image produced by a first rate lens through an inferior add-on.
garyrhook wrote: I believe most, if not all, will work in crop mode. This provides compatibility with crop-mode lenses (DX lenses for Nikon, e.g.) and avoids vignetting.
Joves wrote: Well I read somewhere I think it was on Nikons site that you can use the newer FX cameras in crop mode with an FX lens. It was in the specs for the new 80-400. But to me this would seem stupid because of the newer cameras pixel density. Which means you can crop a whole lot more without a loss of IQ.