Which lens is should I buy.

[ftico]

I have a 70D and I shoot mostly birds. I find 400mm is (at least) what you want for birds (yes, on crop), unless you shoot from a blind, or target only large ones.

So among your options, I would go for the 100-400. I bought a 400mm 5.6L and have been very happy with the results, but beside the moon or the occasional sun setting, you don't get to shoot much else than wildlife (and in that case you often have to crop a lot anyway). If you'd like something you can use to shoot the occasional portrait, or landscape, I'd say the 100-400 is a good compromise -- and it is stabilized (while it is not that helpful for taking sharper pics of birds, since you're gonna want to shoot at least 1/800-1000, it is very useful for properly framing a photo @ 400mm).

I have a 70-300, but the reach is just not enough for most photo-hunting scenarios. I still use it for captive animals.

Good luck!

 

[Inquisitor]

First I would decide if 300mm is enough. Then what type of lens I prefer fixfocal or zoom.

300mm:
Tamron 70-300/4,0-5,6 VC USD
EF 70-200/4,0L IS USM + 1,4x Converter

400mm:
EF 200mm/2,8L USM + 2x Converter (only secondhand, very good and cheap)
EF 200mm/2,8L USM II + 2x Converter
EF 70-200/2,8L USM + 2x Converter (only secondhand)
EF 70-300/4,5-5,6L IS + 1,4x Converter
EF 100-400/4,5-5,6L IS USM
EF 300mm/4,0L IS USM + 1,4x Converter
EF 400mm/5,6L USM (has a similar bokeh to 500L and 600L)

 

[Albi86]

I voted for the 70-300 L.

However, if price is a big concern, I would take the Tamron 70-300 VC USD. Very good lens and it's 1/4 of the price of the Canon L.

 

[fragilesi]

I voted for the 70-300 L.

However, if price is a big concern, I would take the Tamron 70-300 VC USD. Very good lens and it's 1/4 of the price of the Canon L.

My vote goes for the 70-300L to ocover that range of photography which is similar to most of my own. I have a 70d (similar AF system) and it works fine in AI Servo mode which is my most used too.

 

[bod]

I have no experience with longer lenses, but as far as i know "bird photography" and "walk around lens" can't be attributed to the same lens.

+1
I prefer primes and have and value the very good 300 f/4L but for me it is not in most circumstances a "walk around lens". Before settling on a lens at this focal length I tried it out and the 70-200 f/2.8L x1.4, 70-300 f/4-5.6L. I thought its IQ at 300 was the best but was impressed with the 70-300 zoom also. Obviously the 70-200 f/2.8 is a superb lens but with the x1.4 attached it is much heavier and a more expensive lens to buy. It is more flexible than the prime in terms of focal length but in my case I would use a different lens if I wanted a shorter focal length. My logic was that for wildlife, the zooms would be parked permanently at their long end and so the 300 f/4L is a lighter and better choice for me. My experience so far with "bird photography"is that 300 is not enough.

 

[noncho]

I wanted the same as the author - good long lens for wild and walking around with 60D.
There is no perfect choice for that, but I end up with old Sigma 100-300 F4 + 1.4 extender.
And it's good not expensive option for me. 70-300L would be better(picture and IS), but a stop darker(no AF with extender) and more expensive.
Samples:

Bird, 420 5.6 wide open (300+1.4 extender)

Landscape 250mm

Autumn leaves ~200mm

 

[iaind]

You will need 400mm

Don't think 75-300 accepts extender