Are Z lenses APO lenses?

Started 6 months ago | Discussions thread
SrMi
SrMi Veteran Member • Posts: 4,216
Re: Are Z lenses APO lenses?

LarsHP wrote:

ipopov wrote:

APO (apochromatic) has never meant "no LOCA". The term was introduced by Zeiss to mean "chromatically corrected for three wavelengths". This does not mean "no LOCA". In fact, non-APO lean can very well be better in terms of CA that a true APO lens (by original Zeiss definition).

This is not entirely true. It means free of chromatic aberrations (as well as spherical):

https://www.merriam-webster.com/dictionary/apochromatic

It was Ernst Abbe at the Carl Zeiss factory, who in 1886 coined the term when inventing that type of lens correction, which means it "eliminates both the primary and secondary color distortion" (color distortion = chromatic aberration) :

https://en.wikipedia.org/wiki/Ernst_Abbe#Life_work

In other words, it does mean free of longitudinal chromatic aberrations, since that is a type of chromatic aberration.

I like the Wikipedia definition better:

An apochromat, or apochromatic lens (apo), is a photographic or other lens that has better correction of chromatic and spherical aberration than the much more common achromat lenses.

The absolute definition used by Merriam-Webster does not make sense.

Here is also an interesting article by Zeiss:

Achromat and Apochromat – What is the Difference?

Apochromat is a lens with special glass types to bring the three different colors to the same focus. A 100% success is not a criterion.

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