[wim]

I was in a similar quandary a bunch of years ago.



However, because I dont want to carry a lot of heavy lenses from 200 mm upwards, and since the other lenses are similar in maximum aperture to the 100-400L, I ended up choosing that one. This after a short flirt with a Sigma and a Tamron 200-500 (which were not nearly as good as the 100-400L). The IS is very useful, and if you hold it correctly, you may be able to get 3 1/2 to 4 stops of handholdability out of it (I get > 50% sharp shots at 1/45 s with it, on APS-C - I found that I needed 1/1000s with the Tamron at 500 mm to achieve the same).



Í use it for lots of things: landscapes, flowers, sport, macro. Macro because it gets quite close to start with, and secondly because with a 500D closeup lens it allows one ot shoot at 1:1 with a 50 cm + WD, which is great for skitty insects and other nervous animals.



Despite people complaining about mounting a filter on it, mine carries one all the time (prior to last year a B+W UV MRC F-Pro, and currently a B+W X-Pro), for protection purposes. Never had a problem with that.



Currently I am on my second specimen: several years ago I had to part with my first because iIneeded some money fast, but when I could afford to get another one, I did.



For my hobby I really am a prime shooter, basically because I see pictures in primes, and I also treat a zoom as a variable prime, but this is the only zoom I own for APS-C/APS-H and FF.



The picture below was shot on a 1D III at 400 mm, F/5/6, handheld, through a double glass pane, and cropped quite heavily. Lost a little contrast, but very easy to fix in PP:







The next one was shot with 1.4X non-reporting converter mounted, 1D III, at 400 mm, F7.1, handheld, slightly cropped.





Next one at 400 mm, F5.6, 5D II, handheld, in difficult lighting conditions (dusk), no cropping:









Next one on APS-C, 350D, at 400 mm, F/11, tripod:







And this one was from the same session, with 350D at 275 mm, tripod, cropped a little at the right and top, because it was fairly windy and part of another flower blew into the composition <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />:







All processed on a calibrated monitor, BTW, so they may seem rather light and orangy on an uncalibrated monitor.



Unless you want to do BIF only, I would always suggest the 100-400L, and even more so since you also want to shoot fox and mink. I also think the IQ is not too shabby either - you can see why above.



Finally a few remarks on using the 100-400L: always loosen the friction ring completely when shooting - it makes for very rapid (pump action) zooming, which is extremely useful when trying to track something or get it into the frame in the first place. The balance of this lens is exceptional, provided you hold it correctly, by the focusing ring. This not only allows for extreme fast zooming, because both rings are connected, but also for that little extra manual twist possibility to guarantee optimal sharpness if necessary on the spot where you want it rather than the AF system. And the good blance gives oen an extra stop or one and a half on the IS which provides about two, at least IME. Last but not least, do give the IS 1 to 1 1/2 seconds to engage properly for optimal use - it pays off.



Kind regards, Wim