Next Level Lens for Aircraft Spotting

Greetings everyone!

I have a T2i and an 18-135mm lens. I also have an old Quantary 70-300mm TeleMacro zoom lens, but the auto focus system has not been functioning for a very long time, making it only useful for still subjects. I go spotting quite a bit at KORD. There is only one spot at O'Hare that my 18-135mm can handle, but there are others that I would love to try. I go to some airshows as well and even at 135mm, the aircraft don't even come close to filling a full frame. Therefore, I am in the market for a new lens that is a step up from the 18-135. I am also on a tight budget.

I am currently looking at the EF-S55-250mm f/4-5.6 IS lens by Canon, as well as the EF
75-300mm f/4-5.6 III USM, EF 75-300mm f/4-5.6 III, and the EF 100-300mm f/4.5-5.6 USM. I am having trouble on deciding on the one to get. I would absolutely LOVE to get a 100-400mm L lens, but that is way out of budget (maybe in a few years).

Any recommendations or comments welcome!

Regards,
Kevin B.

Back when, everything was manual, including focusing, so that statement could use some more thought. And most of your "Aircraft Spotting" will be at/near infinity, which makes it even easier as the depth of focus there is pretty deep if you're stopped down at all. You just need to get used to it.
In your place, I'd think about a 1.4X teleconverter.

Thanks for the info.

About the teleconverter, would this be the one you are talking about - http://usa.canon.com …nder_ef_1_4x_ii​i#Overview ? The product page seems to imply that it will only work on Canon's super telephoto lens. Will it work on my 18-135mm?

That one.

IDK. I expected that you'd use it with the longer lenses.

Ok, thank you.

FSXHD wrote in post #11085968
I would absolutely LOVE to get a 100-400mm L lens, but that is way out of budget (maybe in a few years).

Consider a Tokina 80-400mm. Sells for US $500. Air show images from the Tokina as mounted to a XTi:

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Thanks! This will definitely be taken into consideration.