What does ASPH mean to you?

[zuiko85]

Meh.
Even some single or doublet molded plastic lenses on simple cameras can have aspheric surfaces. You can tell by the way the surface reflects light.

 

[Darthfeeble]

You should include the choice for "I have no idea really".

 

[Dan Daniel]

I've always enjoyed this "Tessar" from a Nokia phone. Hard to believe it can even make an image, but I guess those aspherical elements do some kind of magic. I wonder if there is even one true spherical surface, even for brief sections of an element-

 

[Sumarongi]

hmmm, it's an acronym?

Perhaps:

A Serious Photographic Hoax

 

[Scottboarding]

Not spherical is generally what comes to mind

 

[Ko.Fe.]

Ultron 28 1.9 ASPH. Smaller than previously owned 28 2.8 III Elmarit-M. Less expensive as well.
It is not as good as Elmarit-M on darkroom prints, but not flat.
On digital M it is smooth lens. Some are saying it is as good as Summicron 35 f2 ASPH.
Most of my "Hamilton as i know it" color shots were taking with this lens.

Ultron 35 1.7 LTM. This lens was better lens than CS 35 2.5 on prints.
No harsh contrast and it was not flat rending lens at all.
They say VM version of this lens is better comparing to Leica and Zeiss.
I think, it is possible to add focus tab to LTM version. With this it is best 35 RF lens for price and performance. For darkroom prints. IMO.

Nokton 50 1.5 VM. Great lens on prints and on BW digital. More alive lens comparing to sterile Planar ZM, Cron Rigid and IV in BW.

Summarit-M 35 2.5 ASPH - best lens I ever owned and have negatives to print from.
Even better than 35 1.7 Ultron LTM I owned before it. It is not about distortion free and such, which this lens isn't great, but very pleasing rendering of small details, edges and contrast on darkroom prints. It simply gives more on the print, but nothing too sharp.
I'm not using it much on digital M, camera I not using much in general. But it is very good, nothing retro or clinical.

 

[xmas_one]

https://en.m.wikipedia.org/wiki/Aspheric_lens

 

[jarski]

Now, what is APO then, in layman's terms?

 

[bayernfan]

Now, what is APO then, in layman's terms?

it makes the red, blue and green lines play real nice with each other.

 

[Rob-F]

Now, what is APO then, in layman's terms?

The full term is "apochromatic." It means that the three primary colors, red, green and blue, all come to a focus in the same plane. A non-APO lens might typically bring only two of three primaries (such as blue and green) into sharp focus at the film or sensor plane.

 

[Freakscene]

What does ASPH mean to you?

Like Vienna it means nothing to me.

It strictly means that one or more of the lens element surfaces are, as pointed out, made with multiple radii of curvature.

It usually means onion-ring bokeh to me.

This is annoying. There are methods to polish elements to avoid this, but lens manufacturers typically don't employ them.

This is from a 35 Summilux ASPH (the pre-FLE one). Annoying, it looks weird.

The full term is "apochromatic." It means that the three primary colors, red, green and blue, all come to a focus in the same plane. A non-APO lens might typically bring only two of three primaries (such as blue and green) into sharp focus at the film or sensor plane.

Technically correct, but often used as marketing nonsense, because none of the camera lenses available today are really apochromatic. Microscope and technical lenses are another story.

We should all stop worrying. Go out and take some photos (ASPH lens or not, whatever you like), and show us.

Marty

 

[michaelwj]

Now, what is APO then, in layman's terms?

In X-ray microscopy (my field) we have two (main) ways to focus X-rays.
The first is a Fresnel Zone Plate, which is a refractive lens. The focal length is a function of the X-ray wavelength, f=(2r*delta(r))/wavelength. So as the wavelength increases, the focal length decreases: It is a chromatic focus.
The second is a Kirkpatrick-Baez mirror pair. The focus here is dependent on the curvature of the mirror, and the wavelength does not figure into the calculations. You can change the wavelength and it does not change the focal length. It is a true achromatic.

In camera lenses, achromatic was first used as an approximation of a true achromatic lens (they converge two wavelengths). Apochromatic was invented for photography (it's not a true scientific word), to distinguish lenses that did a better job than the original achromatic lenses did (they converge three wavelengths). Interestingly, you might think that the three wavelengths would be red, green, and blue, but it doesn't have to be the case, they can include IR or UV (telescopes often include IR for example). Given the looseness the term APO is used in photography, I wouldn't be surprised if this applied to photographic lenses too.

 

[markbakovic]

This is annoying. There are methods to polish elements to avoid this, but lens manufacturers typically don't employ them.

This is from a 35 Summilux ASPH (the pre-FLE one). Annoying, it looks weird.

that looks a bit like cavity resonance to me a la Fabry-Perot, like a surface pair is locally close to plane parallel. If so that might be unavoidable with the geometry in question. (I say this in part because the image looks near-monochromatic: does it still do it with white, with no colour fringing "in the onion rings"?).

If you mean the method of "machining" aspheric surfaces with a diamond stylus and then not smoothing the grooves, I guess this is one way to avoid too much cost increase: if you look at optic catalogues and the same-size, same-glass, same-EFL, same-surface tolerance precision asphere is 2-5x the price of the corresponding spherical item that input cost has to either be passed on to the consumer or reduced somehow. I guess it boils down to microfacets left on glass or moulded plastic (at least index matched caps) or less money spent elsewhere (or price hike).

Now, what is APO then, in layman's terms?

I see what you did there

To be fair though I don't think you could really get away with designing a lens with, say violet, red and like 740nm or so (which might be reliably picked up by most IR films) brought to the same focus but a huge excursion peaking at 500nm, call it APO and rake in the dollars. But yeah, the similarity in terms of marketing the method rather than the results is... uh... hard to overlook

Once again: I'm not talking about specific lenses which are or are not marketed as ASPH, APO or anything. I'm not insulting your decision to use, or not use any lens so marketed or opinions of same. I'm talking about what, if anything, that marketing implies to you as a consumer. Most of the responses so far have been useful, illustrative and/or entertaining.

 

[pgk]

I'm talking about what, if anything, that marketing implies to you as a consumer.

The simplest implication is that the design is relatively new and that the lens has been designed with an aspherical surface to improve it in some way (I know that this might mean improve its marketability) so that its performance should be improved or there is another advantage gained (size, weight, production cost, etc.). Like any other 'designation' aspherical/aspheric/asph. is something which appeared as designs took advantage of such surfaces, mostly to differentiate them from older ones, but which has inevitably become something used to try to drive sales. It's interesting that Leica did not immediately use the designation on their more recent Summarit range, almost as though it is now becoming just another tool in their optical designer's options. Perhaps it's now moving away from being a new marketing tool and into the normality of lens design.

 

[phofseth]

My first associative response was to recall the ancient Kilfitt 90mm macro which had an element with two radii.

My second was to recall the last LeicaR 35-70 which had a "secret" aspherical element in the sense that no advertising bothered to mention it.

In the first case concentric rings can be observed, in the second, no particular peculiarities.

p.

 

[Ted Striker]

The very basic Canon and Nikon 18-55 kit lenses both have an aspherical element. Your phone's lens has several. In fact it's rarer for you to see a spherical design than aspherical today, since the later has become so cheap to manufacture.

So the term does not guarantee anything but (mostly) marketing. Which in fact is a Leica (of which the path is followed by CV) specialty. Most of the Japanese manufacturers didn't even bother with it and other terms like FLE (in Nikon's literature, CRC) anymore after the 1980s', during which these technologies became widespread. They've got more posh words to play with now.

That's not true at all. Fujifilm camera lenses have the word "Aspherical" stamped all over them and Canon and Nikon literature prominently highlight the presence of any aspherical elements in their lens designs.

 

[David Hughes]

While you are all here can I ask if the advent of optical grade plastic meant that a lot of glass compound lenses were replaced by one plastic lens?

I'm thinking of the triplets that look remarkably like the "4 in 3" glass Tessar.

Regards, David

 

[Bill Clark]

What does ASPH mean to you?

No meaning for me.

Lot of marketing/sales used to justify higher prices.

Maybe the most help with wide angle lenses.

But my Nikkor 20 I bought in 1972 works just fine for me, when I need it, rarely. It’s not ASPH.

Interesting article of injction molded plastic lenses:

https://www.lenseloptics.com/plastic-optics/

Taiwan manufacturer:

https://asia.nikkei.com/Companies/LARGAN-Precision-Co.-Ltd

 

[steveyork]

The aspherical lenses I have used (Leica and Voigtlander) have all been very sharp and clinical. Great, I suppose, for color film, but I find them a bit jarring for B&W film.

 

[markbakovic]

While you are all here can I ask if the advent of optical grade plastic meant that a lot of glass compound lenses were replaced by one plastic lens?

I'm thinking of the triplets that look remarkably like the "4 in 3" glass Tessar.

Regards, David

It'd still have to be two different plastics to have two different refractive indices, but if, say, the original cemented pair was two glasses with (probably high) dispersion characteristics that together (nearly) cancelled some other part of the system; that might be replaced by a single lens of a similarly dispersive material (which some plastics probably are). After all the Tessar is a modified triplet so you may well be right AFAIK.