Aspherical Lens??

[rmh159]

I was browsing Adorama.com this morning for a new standard zoom lens (I'm looking for a 2.8 Nikon mount lens if anyone has a suggestion... $500-ish) and noticed a few lenses had "Aspherical" in the description. Could someone explain what it is and if there are benefits / drawbacks to it?

 

[RMThompson]

It's a favored trait to reduce the amount of distortion:

Wikipedia:

The asphere's more complex surface profile can eliminate spherical aberration and reduce other optical aberrations compared to a simple lens. A single aspheric lens can often replace a much more complex multi-lens system. The resulting device is smaller and lighter, and possibly cheaper than the multi-lens design.

 

[JDP]

If I remember correctly, the lenses that are hand ground & polished are labeled Aspherical by Nikon. Though technically, all lenses are aspherical.

 

[rmh159]

Man... I always forget to check Wikipedia.com. Thanks for the response!

http://www.adorama.com/TM1750NKAF.html This is the lens I was oogling if anyone has any opinions.

 

[JDP]

Ah, that's the lens I'll be getting fairly soon, unless I decide to fork out the dough for the Nikon version. Heard nothing but good things about it.

 

[Big Mike]

Great lens, I've got one.

 

[fmw]

If I remember correctly, the lenses that are hand ground & polished are labeled Aspherical by Nikon. Though technically, all lenses are aspherical.

Aspherical lenses don't look anything like spherical lenses at all. They are a completely different animal and that difference has nothing to do with polishing. It has to do with the shape of the lens. As mentioned above, their purpose is to better correct optical aberrations than spherical lenses.