Originally posted by 8540tomg Very impressive Scott. Some of the best TC images I've seen.
Hi Tom,
About 90% of my shooting is of birds, and a majority of the time, I'm using one or more TCs. There's always a considerable amount of TC dismissal that goes on in photo fora, and I think that much of that is due to living in the past.
With cropped senors, only the center portion of the image circle is used, so a lens that's superb in the center and excellent at the edges on film will be just superb to (exc +) on an APS-C body. The TC magnifies the center of the image circle, so it's acting on the best of the best part of the image projected by the lens. My feeling is that with premium glass, and a quality TC there is little or no image degradation. I've actually stacked the F !.7x AFA on top of 2 1.4x TCs with the FA*300/2.8 and gotten acceptable results -- and the AF on the K-7 still worked at f9.3 max Av with it's improved sensitivity!
With birds, small ones especially, this works out better than cropping for a couple of reasons: Given the relatively large size of the AF sensor point in Pentax bodies, a TC enlarges the subject , so increases the chances for the AF sensor to get it really right. This also applies to the metering sensor so it's also easier to nail the exposure regardless of metering mode used. For wildlife, it's difficult to get really close, so unless one wants to use setups, hides, and/or camo, you need the reach -- then get as close as you can, but rely on the reach to get the majority of shots.
Scott