Hello all...
As promised, a side by side performance of the Canon 70-200mm f4L lens with and without the Canon EF 1.4x Extender.
Both Pics - iso200 @ f5.6, single 10 minute exposures, Canon 40D.
Pic #1 Eta @ 200mm
Pic #2 Eta @ 280mm (with 1.4x extender)
(Taking 1.6x crop factor into consideration, in reality 280mm and392mm FL)
File compression has lost critical detail, but there seems to be very little degradation in image quality with the addition of the 1.4x extender.
On close inspection of the uncompressed TIFF files, there was a slight softening of stars at the extreme edges of the field - but not worth worrying about. No increase in CA either
Very impressed - nice solid feel when attached to the camera too.
Hope this helps some.
All the best
Doug
ps...there's a 70-200mm for sale in the trade section right now if anyone is interested (not mine!)