Steve's Digicams Forums

Steve's Digicams Forums (
-   General Discussion (
-   -   What does Sigma mean by APO? (

j_riederer Jul 10, 2005 11:32 AM

I am looking and for a Sigma lens with APO it is roughly $80 more, what is it? Thanks in advance!

Dave Chrismer Jul 10, 2005 2:29 PM


A lens or optical system virtually free of chromatic aberration,

Stevekin Jul 10, 2005 2:41 PM

APO stands for Apochromatic.

It is a lens corrected for chromatic abberations in all three primary colours. (Helps to reduce this).

CA is causedwhenthe lens can't focus different colours on the same focal plane, causing a 'colour fringe' around objects.

Whether or not it's worth paying extra for I can't say. But I can say my prosumer has an APO lens and I don't see any CA in my shots/prints.

I'm sure someone else will add to this regarding your DSLR.


Dave Chrismer Jul 10, 2005 2:45 PM

The blue fringingaround the openings where the light background shows throughis an example of C.A.

Stevekin Jul 10, 2005 3:16 PM

That's a good example Dave has shown. An APO lens will reduce the vast majority, if not all of this happening.

G35Guy Jul 10, 2005 3:35 PM

If you plan on doing anything beyond looking at your own pictures, I would highly recommend a lens that is apochromatic. Otherwise, people will ask you why on earth every bright area in your pictures is edgedwith violet. And, being that you're into nature photography, it's probably even more important, as you'll be taking pictures in sunlight, which makes CA more likely.

All times are GMT -5. The time now is 11:26 PM.