Help me choose my next wildlife lens please

Tom, I'm afraid I have bad news for you. Your only option is the 100-400 lens. The other two will not autofocus on your camera (the TC's create f/8 equivalents).

Look on the bright side - the 100-400 is optically the best zoom lens a mortal can afford in that range.

Not just AF would be a victim of the TC route. Unless you expect all your shooting to be from a rock solid tripod and of non-moving subjects, either TC on either of both shorter zooms sacrifice some sharpness compared to the 100-400 at pixel peeping level, due to combined effects of the add-on optical magnification and smaller wide open apertures. Because of the latter you'll have to make more compromises between slower shutter speeds or shooting closer to wide open more often. Plus, the TCs will also magnify any chromatic aberration that occurs.

But take heart, 3 lbs really is not that heavy for a long lens... 6 lbs and above, now that's what you can call heavy! ;)

Or you wait for the EF 200-400mm f/4 L IS USM with built in Extender 1.4x.
http://www.the-digital-picture.com/Reviews/Canon-EF-200-400mm-f-4-L-IS-USM-Extender-1.4x-Lens-Review.aspx

Tom,
I'm not a Canon person, but at your price I would consider the Sigma 150-500mm f?-6.8. True its a bit slow, but it's not bad and I have caught a few flying birds with it. You'll need a good tripod and head though. So the lens is around $1000 (new), a good ball head in the $300 range and maybe another $300 for a good tripod.

Just a thought. You'll appreciate the reach anyway.

Doug

There are a few misconceptions about the 100-400. The weight isn't too much different from your other options. It being a dust magnet is grossly overstated. I have the lens, used it in several African places and never noticed dust problems. Remember, all lenses have moving lens groups so most of them will take in some outside air. The weight of these lenses can't be ignored. No problem during short walks but later this year I'm planning a hike in the Himalayas, the 100-400 will stay home. I'm not going to carry 1.5 kg over passes with a height over 5000 meters. In your case I would seriously consider the 100-400 but YMMV.

Option 3. Canon A EF 70-300mm f/4-5.6L IS USM with a 1.4x EF Extender III. Total Cost = $1750

I have the 70-300L. It's a great lens. It is not compatible with the Canon extenders.

The 300/4 IS might be another contender. The 70-300L focuses significantly faster, but the 300/4 will take a 1.4x extender. That slows the 300/4 focus down considerably, though. (I was never happy with mine with the 2x, though.)

What lenses do you currently use? Are you happy with what you get shooting at f/5.6 at that light level? If so, I can recommend the 70-300L. But if you need a longer focal length, this isn't the lens for you. 300 is really on the short end for most bird photography.

Think about the Canon 400 mm DO IS F4 lens. Some folks are a bit leery of the DO part, but I've found it to be a great lens. It's much lighter than conventional lenses; it's light enough to hand hold for birds, and it's plenty sharp. Of course, price is a consideration, but I've gotten many good years out of this lens. For me, the 100-400 is off-putting because of that back and forth maneuver you have to do to zoom. Just a thought.

Tom,
Some really good advice and considerations given already!

I have had my 100-400 for a few years now and often use it with the 1.4X TC on the Canon 50D, EOS 3 and Elan 7e, and have just a few comments as follows;
1.) I've not noticed any unusual/abnormal dust problems.
2.) IMHO, most long lenses are a bit cumbersome, . . . just something you learn to live with.
3.) When seeking "sharpness," there is a bit of a learning curve with the 100-400, but IMHO, no more so than with any other lens & body combination. BTW, the 100-400, or at least mine is less sharp fully extended to the 400mm. I obtain the sharpest images at just over 300mm whether using the TC or not.
4.) The IS on the 100-400 is pretty good. and I have taken many hand-held shots at Air Shows and even some of my Wildlife and Birds in Flight are hand-held, but a tripod and ball-head are always better when trying to obtain the sharpest images.

If you care to look through my gallery here on PN, I usually display what lens I have used, and often include details on many shots. I most commonly use the 100-400 on the Wildlife, Aviation and even some at the Car Shows that I attend.
Should you decide on the 100-400, I will be glad to share any experience's I have had with this lens.

Cheers & Best Wishes,

Of those choices, the 100-400L is really the only viable option. Note that it will accept the Canon tele extenders, unlike the 70-300L. Of course, you lose AF on the 7D with an extender on that lens. As for having something smaller, well, the lenses are interchangeable for a reason! I also have the Tamron SP 70-300 f4.5-5.6 VC lens, which I use when I don't need the reach of my 100-400L. At under $500 (about the price of a Canon extender), it's tough to beat. About the only other viable option would be the Canon 70-200 f/2.8L IS II with the 2x converter, but that combo is a lot more expensive, and the 70-200 F/2.8L (without the converter) is as heavy and bulky as the 100-400 is. For that price, get the 100-400L and a 24-105 f/4L and have continuous coverage...