Originally posted by Squier I wouldnt mind one of the Pentax A rear TC's to try - maybe the 2X-s or 2X-L ...but they're real pricey.
There's one for sale here at a shop and they want £150 GBP
Make sure before buying an -L converter that the lens is compatible. I lost a shipping fee on a 1.4X-L because the throat of my M 400 is too small, and the L series project into the lens. The 1.4X-S does not project and can be mounted on any lens. I am sure the -L would give me better images than the -S, but it won't take any images when you cannot mount the lens.
I am in the throes of testing the AF 1.7X on all my lenses, and so far I am pleased. The images with the 400 seem just a little bit cleaner with the 1.7X than the 1.4X. I sure don't care for working with a lens with a maximum aperture of f/9.5, though.
I guess I'll have to get a DA* 300/4 to replace my 400. 510/6.8 is a bit better for aperture, but a lot shorter than even 560mm f/8, let alone 680mm f/9.5. LBA strikes again.