Super-telephoto, what is a good lens ?

[philip]

Sorry, I meant 300mm prime, i've got 70-200 on the brain lol.

Well, thats a different story then...different price class as well.

[tinymoon]

The 1.4X Extender work well with EF 100-400L but you loose 1stop. The 2X Extener does not go along well with EF 100-400L and Auto Focus is just pizza. I should say it is not Auto Focus at all (anyway it is not matter due to Focus is always at infinity)

I am thinking of Sigma 50-500 for its extend 100mm or 1.4Extender for my 100-400L. Some say Sigma 50-500 is a very good len with IQ and Built Quality.

[Jet-fighters.Net]

As you are in the Phoenix area try out Tempe Camera on University just West of ASU and East of Sky Harbor. They have a 500 f/4.0 USM for rent that goes for about $150.00 per weekend. The only downside is you have to put a deposit down for the value of the lens or show an insurance rider that would cover the lens.

http://www.tempecamera.com

I have rented from them time to time and have had good results with there service when i lived in the Phx area.

[B787INDIA]

With my limited knowledge, i think your options for Telephoto Zoom Lenses (In Canon) would be the following:

1. EF 70-200mm f/2.8L IS USM
2. EF 70-200mm f/2.8L USM
3. EF 70-200mm f/4L IS USM
4. EF 70-200mm f/4L USM
5. EF 28-300mm f/3.5-5.6L IS USM
6. EF 100-400mm f/4.5-5.6L IS USM
7. EF 70-300mm f/4.5-5.6 DO IS USM
8. EF 70-300mm f/4-5.6 IS USM
9. EF 100-300mm f/4.5-5.6 USM
10. EF 55-200mm f/4.5-5.6 II USM
11. EF 75-300mm f/4-5.6 III USM
12. EF 75-300mm f/4-5.6 III
13. EF 90-300mm f/4.5-5.6

Often pricing is the major factor in decision making process. Hence you can choose
Please note as i follow Canon i have suggested the same, i am following the same platform for integrated photography.

I currently have:
BODY: EOS 40D. EOS 400D.
LENSES: EF-S 17-85mm. EF-S 18-55mm. EF-S 55-250mm f/4-5.6 IS and EF 100-400mm f/4.5-5.6L IS USM.