Abbreviation: ASP = "Aspherical Lens" (Sigma)

The abbreviation ASP means "Aspherical Lens" and is seen on Sigma products.

Explanation from Sigma

The aspherical lens complex allows freedom of design, improved performance, a reduced number of component lenses and a compact size.

This lens provides high optical performance while maintaining a compactsize. For example, the 12-24 mm f/4.5-5.6 EX DG ASPHERICAL lens widensthe range of wide-angle lenses, and it provides distortion-free images withimage reproduction performance equivalent to that of a single-focal lengthlens. Aspherical lenses allow the production of high-quality images fromcompact, lightweight telephoto zoom lenses.

See examples of effected products

	Sigma EX 24mm F1.8 DG ASP Macro
	Sigma EX 20mm F1.8 DG ASP RF
	Sigma EX 28mm F1.8 DG ASP Macro

See links