image quality of a tele-converter

[camera eye]

My most tele lens is a Sigma 180mm macro. Next
weekend I am going to the Dayton air show. My question is do I buy a converter or is image quality bad enough with one that I should buy another lens. Consider I rarely have a need for anything beyond 180mm. Based on past experience I feel 180mm won't be enough to pull it in.
thanks

[RichardtheSane]

For not a lot more than a tele converor you could buy yourself a sigma 70-300 DL lens. The image quality would be far better than with the convertor and you have another lens in your arsenal to boot ;)

[camera eye]

its funny you mention that lens because thats one of two I have narrowed it down.
thanks man

[robertwgross]

I have a Sigma 170-500mm zoom. It works good, but you better have the optional trailer to haul it around.

---Bob Gross---

[camera eye]

on your 170-500? this lens was my first consideration.
Is it soft in the 300-500 range around f/8?
thanks

[RichardtheSane]

A friend of mine got the sigma 70-300 super DL macro for his kit, and I must say I am fairly impressed with the results he is getting. It is about as sharp and my canon 100-300 USM (but not my 100-400L ;) ). For the money there is a lot of lens there, and if you don't need that focal length often then it comes highly recommended.
:)