Whisch lens to choose?

[Mickw]

Hi Bob and all, need some help. Been doing photography for 2 years. Its only a hobby, im no pro, just a dude who finds photography a great way to escape from a stresfull job. My main interest has always been mono, industrial, gothic stuff, never had an interest in wildlife. Until now.

Took one of my patients out to a wildlife park as he likes taking pics of birds. Went to a hide. Something clicked in my brain and i couldnt stop thinking of taking pics of wildlife. So....

I visited a few local hides and was blown away by the stuff i saw. I had seen some very cool pics on here and at my local club and whilst i know how to take wildlife pics ive never had an interest till now. My problem is lens choice.
 My gear is...
Canon 5D
180MM f3.5 Macro
70-200 f2.8 IS L
16-35 f2.8 MK2 L
24-105 f4 L
Canon 400D

I love Canon Pro gear as its touch and takes the knocks. My problem is dont have the reach for bird photography Even with my 1.4 converter. Ive looked at lens choice and talked to people so from what ive seen i have a few options.

Sigma 150-500 OS. Got the reach but not to fast and not as tough as an L series. Also auto focus issues.
Sigma 50-500 better in low light but no stabilisation which i may not need anyway, the stabilisation i mean. A good lens but again not L series quality.
Canon 300 f4 L. Quality, sharp, autofocus ok but not the reach.
Sigma 500 f4.5 Prime. Prime quality but again its not a Canon L series.
Canon 500 f4 L The best but id have to save for a year to buy one.

I really rate your opinions Bob and the L series gear i use has been excellent. Rain wind and dust, never let me down. My hunch is go Sigma, get the experience then go Canon. But i really rate my Canon gear.

Ive read your reviews. Any advice?
And before anyone gives me a bad time over such choices as has happened on certain forums, i love photography, yes i know how to take a good pic, yes ive got money etc etc etc. I just want advice from a top pro.

Mick

[dwdong]

The two items that might be also worth considering are a Canon 400 f/5.6L and a 50D (for the 1.6x).

[Bob Atkins]

If money is no object, then it's a "no brainer" with the EF 500/4L IS USM.

Otherwise maybe I'd look at the Canon EF 100-400/4.5-5.6IS USM if you want a zoom, or the EF 300/4L IS USM(along with the EF 1.4x II ). Both are sharp. The 300 has a speed advantage as long as you only need 300mm and makes a great autofocus 420/5.6 with IS when used with the 1.4x.

Going with an EOS 50D will also give you a slight advantage over the 5D in this case since you'll get  more pixels and a smallerframe size which will give you higher magnification. A 400mm lens on an APS-C sensor camera would be like a 640mm lens on your 5D. Even your 400D will probably be better then your 5D if you need to crop your 5D image because your lens isn't long enough (and for birds, it never is long enough!). The 400D has the same sensor size and pixel count as a 40D. I have a 5D and a 40D. When I want maximum telephoto reach I use my 500mm on my 40D. When I want to shoot portraits, macro and landscapes, or if I can fill the 5D frame with the subject using my available telephoto lenses, I use my 5D.

The Sigma lenses are possibles, but the resale value on them is generally lower than on Canon lenses, and I don't think the performance is quite up to that of the Canon L lenses, especially at the longer focal lengths.