What does the following mean

[Rob300D]

May sound like a stupid question but Can anyone tell me what the following mean lense wise:

APO:confused:
ASP:confused:
RF:confused:

Thanks Rob

[Andy_T]

APO ... apochromatic element ... something Sigma puts into their better lenses ... to help get correct colours, if I remember correctly
ASP ... no idea
RF ... rear filter?

Guesswork, really.
You might google for it.

Best regards,
Andy

[Mogwyth]

Sigma lens abreviations

APO=Apochromatic design and Special Low Dispersion glass minimises colour aberation and improves contrast and sharpness.

RF=Rear focusing only the rear lens of the group moves when focusing, used in wide angle lenses

ASP=aspherical lenses that are not spherical, results in less elements in a lens group maximiseing optical performace while reducing weight and reduces lens flare and edge distortion

:) Not stupid to ask, stupid to remain ignorant. :)

:lol:where in Wales are you?