dangriss wrote:
Teleconverter? A 2X could get you out to 500, just losing a couple of f-stops.
There are almost no teleconverters usable with Canon EF-S lenses... Kenko "HD" are the only ones. But a 2X on that lens will mean no autofocus, a dim viewfinder to try to manually focus and I'd expect image quality will be pretty bad.
OP, there's a new Sigma 100-400mm OS HSM lens that costs $800. It's quite compact for a lens with this range of focal lengths.
Alternatively, look for a Tamron 150-600mm VC USD, first version. Those can still be found new and are discounted to $870 for clearance (
https://www.bhphotovideo.com/c/product/1013956-REG/tamron_a011_c_sp_150_600mm_f_5_6_3_di.html). The Tamron 150-600mm "G2"is admittedly better, but costs $1400. The original version is pretty good from 150-500mm, but a bit soft between 500 and 600mm (but better than nothing!)
Or, pick up a Canon 100-400mm original push/pull zoom version.... still available new and now clearance priced at $1300 (
https://www.bhphotovideo.com/c/product/162616-USA/Canon_2577A002AA_100_400mm_f_4_5_5_6L_IS_USM.html). Like the Tamron above, yes, the new Mark II version is improved in a number of ways, but it sells for $2000. The original version is still pretty darned good... just be sure not to put any filter on it. (Oddly, it "goes soft" even when a high quality filter is used... much better image quality with no filter.) KEH has the original 100-400mm used for about $1079. You might find it for less elsewhere, but I think KEH gives a 90 day warranty. Bought used elsewhere might have no warranty.
Canon 400mm f/5.6L is a very sharp, fast focusing and reasonably sized lens that sells for $1150 new and around $850 used. IMPORTANT: this lens does not have image stabilization. It can be used with a 1.4X teleconverter and still autofocus on some Canon cameras: T7i, 77D, 80D, 7D Mark II and all the current full frame models except for the soon-to-be discontinued original 6D.
Canon 300mm f/4L is also quite good and has IS, sells new for $1350, used for around $800. It can be used with a 1.4X TC on all Canon DSLRs and with a 2X TC on the above listed models. (Image quality always suffers more with a 2X, though.)
Sigma made 120-400mm OS HSM, 150-500mm OS HSM and 50-500mm OS HSM lenses in the not-too-distant past, that might be found used in the $500 to $700 range. There also were earlier, non-OS versions that are cheaper... but I'd recommend avoiding them because the image stabilization feature is important on these long focal lengths... especially if you hope to hand hold the lens or use it on a monopod a lot.
And, yes, there was the even earlier Sigma 80-400mm OS that a previous response mentions, which can be found used for $500 or a little less. It has OS., which is a good thing. In fact, I think it was one of Sigma's first stabilized lenses. HOWEVER, a bad thing is that it does not have HSM focus drive (similar to Canon's USM "ultrasonic" focus drive), so the 80-400mm's autofocus is pretty slow and noisy.
If these seem pricey, a few years ago there were almost no reasonable quality, modern autofocus lenses reaching 400mm, 500mm and 600mm that sold for less than $9000. And with most of those you'd also want a $1500 tripod to sit the big, heavy lens upon. So, comparatively, the above are bargains.