Difference?

[darkeen]

Hey, can anyone tell me what's the difference between these two lens? I know one claims to be "APO" but I can't figure out what that means.

http://www.amazon.com/Sigma-70-300m...=sr_1_6?ie=UTF8&s=photo&qid=1262033904&sr=1-6

http://www.amazon.com/Sigma-70-300m...=sr_1_2?ie=UTF8&s=photo&qid=1262033904&sr=1-2

I'm looking for a decent Telephoto for my canon XS.

 

[SilverMK3]

According to the Sigma site:

APO Lens

In order to attain the highest quality images, the APO lens has been made using Special Low-Dispersion (SLD) glass and is designed to minimize color aberration.

SIGMA's APO zoom lenses minimize color aberration. As the refractive index of glass depends on the wavelength of light, color aberration occurs when different colors form images at different points. This problem often occurs with telephoto lenses, but the Special Low-Dispersion (SLD) glass and Extraordinary Low Dispersion (ELD) used in SIGMA's APO lenses helps to compensate for color aberration, thereby allowing them to produce sharp images.

 

[botw]

Get the Canon 55-250. Much better than either of those Sigma's (in that it has better optics and effectibve IS) and is in the same general price bracket.