Comparison of Canon EF 300 f/2.8L IS, EF 300 f/4L IS and the Canon 1.4x MkII TC.
The 300mm f/2.8L IS lens was also tested with the Canon 2.0x MK II TC. Although there is nothing
to compare with, the crops are included for general interest

Conditions:
30D, RAW, MLU, remote cable release, tripod (Slik ABLE 300DX) with equipped with
the standard Slik quick release head, IS was off on the lenses, ISO 1600.
The test was conducted indoors, natural daylight, at a distance of 12 ft to the target.
The shutter speeds ranged from 1/250 to 1/40 at 420mm, so stability on the tripod is very important at these focal lengths.

The camera was allowed to stabilize between sets then 3 shots were taken allowing
6 seconds between shots. The 3rd photo from each set was selected for conversion.

Photos were converted with DPP v 3.3, exposure was increased +1 EV, all other
parameters were set to zero. Converted photos were cropped in Photoshop CS2 with the
Marquee tool to 700 x 700 px with no resizing, resampling or other processing.
Finished crops were saved as JPG quality level 12 and brought into the final composite file,
which was saved as JPG quality level 12.

Legend:
2.8 = 300 f2.8L IS + 1.4x TC
4.0 = 300 f/4L IS + 1.4 TC
2.8 + 2.0 TC = 300 f2.8L IS