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Here you go. As you can see it could be a bit sharper, but it was quite far away.
Steps taken: Converted the rawfile to tiff, no sharpening or anything. Cropped it, saved it as tiff, again nothing else.
Imageshack made a png of it.

Exif: f/18, 1/25 sec @ ISO 100

Should I confuse matters further by posting a 100% crop of the 300mm f/2.8 + 1.4x converter?

Yes!

At the risk of joining a P&*^%ing competition ...

Canon 400mm F/5.6 L at 5.6 and 1/640s ISO 200 handheld.
100% crop from near centre frame. No sharpening or contrast/saturation adjustment, either in camera or post processing (ie camera setting 0,0,0 using Adobe RGB). Simply converted from CRW to JPG using RSE.

I'll post comparisons between my 400mm and the 400mm plus 1.4 convertor in a minute or two.

I did a little test for myself to see the effect of my TC on the 400mm versus what my 75-300 could do. The results are not surprising

Canon 75-300 F/4.0-5.6 EF III USM at 300mm at F/5.6


Canon 400 F/5.6 L


Canon 400 F/5.6 L plus Sigma EX 1.4 TC


In any given situation, I would choose the prime without the 1.4 TC (although the effect isn't too great - I tape the 3 leftmost pins so I still get AF, albeit slow and unreliable). I won't use the zoom unless I have too.

BTW, the test above was done by varying the subject distance to ensure the same image size on the sensor - there was no image manipulation. As before, no sharpening or saturation/hue/contrast manipulation.

I changed from the 100-400 to prime lenses (I initially went for the 300IS and the 135 2. when I changed from a 300D to the 20D. There seemed to be a real problem with this combination with focus - I had many very poor results, much worse than with the 300D.

Having said that, I am much happier with the primes - as has been said, you nearly always use the lens at maximum. I may have been lucky, but don't find dust a major problem despite changing lenses.

I still use a zoom at the lower end (24-70) as that does provide a needed versatility.

Richard

Here are two pictures taken with a 300 f/2.8 IS L, one without a converter and one with a converter. The pics were taken from a tripod using a remote release and mirror lockup. No sharpening was applied during conversion from RAW to TIFF. Both pics are 100% crops.


100ISO, 1/5 sec @ f/11. No converter used


100ISO, 1/4 sec @ f/11. Canon 1.4x converter (Type II) used

The loss of sharpness due to the use of the 1.4x converter is very noticable, it's much worse than I'd expected it to be. I'll do some more tests tomorrow using faster shutter speeds.

I can really recommend the 100-400mm IS. In a trip to the Kruger 3 months ago, it was definately my most used lens and the results were very favourable with my 300mm F4 L and 200mm F2.8 L.

The flexibility of the zoom was the key for my purchase and I dont regret it at all.

The image quality of this lens is very good, yes, I bit soft at the short end, but overall very happy

You will not regret your purchase at all.

Feel free to have a look at
http://delboysafa.smugmug.com/ for some of the pics I took with it

Good Luck.

A bit more ammo for the prime afficiandos - check out this post on Hedrus's site.

I know this is all "laboratory" stuff but it matches my real-life experiences.