What does APO really mean?

[Clandrel]

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Just wondering what APO means. Is it a design feature? Or optical feature?

 

C

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[tgray]

Optical. It means apochromatic.

 

Apochromat - Wikipedia, the free encyclopedia

[lars_bergquist]

That is correct -- as far as it goes.

 

There is no ISO standard that defines what 'apochromaticity' means in a photographic lens. Therefore, the 'apo' designation is not a universal mark of excellence. One manufacturer's apo lens is another's simply well corrected optic.

 

Apochromatic optics were first developed in the early 1900s for microscopy. This means that the angular coverage was small. The definition was just that blue, green and red light came to a common focus on or close to the optical axis. If you did not see the specimen well, you just moved it over a bit, to center it.

 

Obviously, this would not do for photography -- even for microphotography! But most manufacturers of photo lenses do not claim that their lenses are apochromatic over the full image circle -- because they aren't. Now, Leica apply much more stringent criteria. A Leica apo lens has to be 'apo' across a much wider area. Therefore, there are only four Leica lenses that carry the Apo designation: Apo-Telyt 135mm, Apo-Summicron 90mm, Apo-Macro-Elmar 90mm, and Apo-Summicron 75mm. Chromatic aberration becomes more problematical the longer the focal length, so only longer lenses have apochromatic colour correction, Leica style. There are other Leica lenses however that most any other manufacturer would gladly label 'apo', foremost among them probably the Summilux-M 1:1.4/50mm ASPH.

 

The old man from the Age of the Monocular Microscope

[tdtaylor]

Lars, thanks for the explanation- inquiring minds did want to know.

[giordano]

Here's a lens whose spectral range makes the Leica APO lenses seem rather unambitious - and very inexpensive.

 

UV - VIS - IR Multispectral Lens for Forensic and Artistic Applications

[Jeff S]

. There are other Leica lenses however that most any other manufacturer would gladly label 'apo', foremost among them probably the Summilux-M 1:1.4/50mm ASPH.

 

According to Peter Karbe, the 50 Summilux aspheric really is an APO lens. For an interesting discussion, see paragraph 6 in this David Farkas blog post...David Farkas Photography Blog: Photokina 2008 - Day 2 - Taking it easy and getting an education

 

Jeff

[lars_bergquist]

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"But, he [Peter Karbe] thought the idea of an APO 50 was a bit silly so they never put it on the lens or in any marketing materials." (Quote from David Farkas' 2008 blog.)

 

Which company but Leica Camera would reason that way?

 

I own that lens. This extreme degree of correction is what is ultimately responsible for the breathtaking clarity of very fine detail this lens can produce. Thank you, Herr Karbe. And thanks also for the very high degree of resistance to flare and internal reflexes -- especially important in a RF camera where you won't see them until it is too late.

 

The old man from the Age of the Monocular Microscope

[Xmas]

Well a color corrected lens would normally only be corrected for two colors,

 

a bluey green

a yellowy orange

 

you will only get coincidence with the two colors chosen, 'spot' spread with other colors if you ray trace, normally only annoying with longer focus.

 

The little mark on the focusing scale for infra film follows.

 

An apo is corrected for three colours, one might design

 

a UV apo or

an IR apo, or

a blue green red apo

 

depends on what you want...

 

The marketing people then get their hands on it and anything can happen to the sales flyer.

 

Noel

[01af]

Which company but Leica Camera would reason that way?

Minolta.

[jaapv]

Not sure - the long "APO"lenses by Minolta barely make the grade. Typical review: (J.Greely on photo.net)

 

Good news? It balances well, even when extended trombone-style to the 400mm setting, it is reasonably rugged, it has decent sharpness and contrast when stopped down and used on a tripod, and hey, it's a zoom.

[lars_bergquist]

Minolta.

Maybe. And, occasionally, Mamiya. Another lens I have worked with was the 150mm lens for the wonderful Mamiya Six RF camera, and that too could easily have been promoted to apo-dom by a less well-behaved sales department.

 

The old man from the Age of the Monocular Microscope

[giordano]

Minolta.

Earlier, there were the 50mm f/1.8 Switars and Macro-Switars made by Kern for Alpa SLRs in the 50s and 60s. The Alpa literature often described these as apochromats, but as far as I know Kern never did. Certainly the lenses aren't marked "APO".

 

Either way, they don't seem to have been any better than the contemporary 50mm Summicrons.

[ho_co]

According to Peter Karbe, the 50 Summilux aspheric really is an APO lens....

Jeff--

You mean, "According to what David reports Peter saying, the 50/1.4 is an apo." All later claims I've seen on the web that the 50/1.4 asph is apochromatic originate with that affirmation.

 

Erwin Puts differs succinctly with the assessment (Summilux1.4/50 asph): "The color correction is excellent, but not of APO calibre."

 

 

Nowhere in Leica's literature, either marketing or technical, is there a claim that Karbe's 50 Summilux is apochromatic. It is an excellent lens, and its performance may approach that of an apochromat. But by Leica's standard, it isn't.

 

As John said, Alpa claimed that the very nice Macro Switar was apochromatic, but Kern didn't.

 

Leica is still one of the highpoints of honesty in their marketing. Let's try to keep it that way, and not get swept up in questionable claims for Leica lenses.

[Jeff S]

Jeff--

You mean, "According to what David reports Peter saying, the 50/1.4 is an apo." All later claims I've seen on the web that the 50/1.4 asph is apochromatic originate with that affirmation.

 

Erwin Puts differs succinctly with the assessment (Summilux1.4/50 asph): "The color correction is excellent, but not of APO calibre."

 

 

Nowhere in Leica's literature, either marketing or technical, is there a claim that Karbe's 50 Summilux is apochromatic. It is an excellent lens, and its performance may approach that of an apochromat. But by Leica's standard, it isn't.

 

As John said, Alpa claimed that the very nice Macro Switar was apochromatic, but Kern didn't.

 

Leica is still one of the highpoints of honesty in their marketing. Let's try to keep it that way, and not get swept up in questionable claims for Leica lenses.

 

Ok, Howard, so David lied about what Peter said to him. Take it up with him. I don't need the lecture, thank you.

 

Jeff

[ho_co]

In regard to usage: Properly, 'apo' shouldn't be written all caps. It's just the first part of the word apochromat.

 

Example: "Is the LEICA APO-SUMMICRON-M 1:2/75 mm ASPH" an apo?" -- "Yes, it's an apo."

 

 

In regard to the looseness of the definition of apochromatism:

 

In the '70s, Zeiss offered one (or more?) lenses for the Hasselblad which they claimed to be superapochromats. Their literature 'proved' the point with a diagram showing that five (six?) colors were brought into focus at the same plane, not the three required for an apochromat.

 

Of course, the term "superapochromat" was a Zeiss invention that to my knowledge was never accepted by the optical community. It was simply one of Humpty-Dumpty's terms that meant 'exactly what [he] wanted it to mean.'

 

They were very good lenses with a techy-sounding but meaningless moniker.

[ho_co]

Ok, Howard, so David lied about what Peter said to him....

Jeff, grow up.

 

I didn't say that David lied. If you think he did, that's your business.

[Jeff S]

Jeff, grow up.

 

I didn't say that David lied. If you think he did, that's your business.

 

Wow, two lectures in one day. All I did was provide a link to an interview, clearly stating the source as David's blog. But, you apparently didn't like my citation. Then you ranted about my somehow speaking for Leica, which is nonsense.

 

Your post clearly implies that Puts' opinion is more valid than David's discussion with Peter. You could have merely posted another link, just as I did, providing a differing opinion...without the rant.

 

BTW, this is what Peter Karbe says about the lens, forgetting about APO...Shutterbug: The Leica Lens Saga Or, should I say, according to Shutterbug.

 

Jeff