Are Z lenses APO lenses?

Started 6 months ago | Discussions thread
Z6User Senior Member • Posts: 1,215
Re: Are Z lenses APO lenses?

davethebirder wrote:

Z6User wrote:

SrMi wrote:

Some Voigtlander Z lenses are APO (APO Lanthar 35mm and 50mm).

But how are they in practice? As I understand it, APO is a marketing designation.

No, APO is short for apochromatic ...... and are lenses which are corrected against "longitudinal chromatic aberrations" (LCAs) ....... ie CAs caused by distance (Z axis) ...... usually red fringing in front and green behind the plane of focus, .....

APO is a real optical term and these corrected lenses should not suffer from LCAs ...... manufacturers are quite rightly quick to designate their corrected glass as APO ......

I am well aware of the meaning of apochromatic. However, lenses that have the term APO do not always perform as well as one might expect. That can be because the lens is not a true apochromat ie APO does not directly equate to apochromatic.  Hence my statement that it can be a marketing term. In the case of a company such as Zeiss, one might expect the lens to perform as expected. I have a Sigma 400mm F5.6 APO Macro lens, which in truth is neither apochromatic, nor capable of true macro work.

Incidentally apochromatic implies a high degree of correction for spherical aberration as well as chromatic. And I don’t believe that it implies perfect correction of OOF CA. It simply indicates that the lens is corrected for three wavelengths in the plane of focus, as opposed to two for an achromat.

........... neither of the following are APOs!

Sometimes manufacturers use APO when a lens is only partially corrected ....... ie the Sigma 150mm F2.8 macro APO where slight LCAs still remain .........

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