stacking converters

[blade912]

July 12, 2008 at 9:22 am

I am wondering why canon advise not to stack converters, as 1.4 and a 2 onto a 400mm f2.8 would make a impressive lense of f8 1120mm as long as you use a extender in the middle.

Any ideas why

[paul]

July 12, 2008 at 9:26 am

Probably because it’s slow (f/8) and the image is quite soft due to the double magnification.

I’ve done it once or twice, just to test. A 300mm f/2.8 with 2x TC and 1.4x TC too. A nice 820mm f/8. But, the image was soft and a moving subject is almost impossible to focus on.

[blade912]

July 12, 2008 at 9:47 am

You would get away with the softness with wildlife shoots as long as it’s a sunny day and Photoshop is used, but I noticed that a few of the camera readings were wrong, the biggest f number was f5.6 instead of f8. So the camera doesn’t recognize that there are two converters used and this could cause some kind of malfunction

[paul]

July 12, 2008 at 11:29 am

I didn’t have that problem. The camera did have a max aperture of f/8 on mine.