Do not use the APO Tele Converter EX on top of another APO Tele Converter, or any other kinds of converters.
Using the APO Tele Converter EX decreases the effective aperture by one F-stop (with 1.4x Tele Converter) or by two F-stops (with 2x Tele Converter). However, exposure can be determined in the same manner as when using the master lens without a Tele Converter.
* 1.4X 2X.
* Lens construction 5 elements in 3 groups 6 elements in 5 groups.
* Focal length 1.4x that of a master lens 2x that of a master lens.
* Aperture coupling range F2.8 - F32 F2.8 - F32.
* Reproduction ratio 1.4x that of a master lens 2x that of a master lens.
* Weight 143g (5oz.) for the 1.4x and 234g (8.3oz.) for the 2x.