Aspheric lenses / elements - REALLY ?

[dcsang]

I'm a complete non-technical gear guy when it comes to lenses/elements - I've got my non-ASPH lenses and I know the ASPH element lenses are more expensive and all that but I'm curious about why the difference in cost.

Is it a more expensive manufacturing method?
Is it merely a reason to charge more (i.e. more profit for putting in ASPH elements)?

And, based on my lenses only mind you, save for the 35mm pre-ASPH summilux, the 50mm pre-ASPH lux and the 90mm pre-ASPH cron are way sharp; so is the whole thing on sharpness of ASPH lenses just a bit of a marketing tool more than anything?

I'm just curious about this.. so any input is welcome.

Cheers,
Dave

 

[ferider]

Regarding optical quality, the rule of thumb is one asph element replaces two spherical ones.

Regarding costs, there are several ways to do it, at different manufacturing costs. From the most expensive hand grinding over molded and polished glass to the least-expensive resin/glass compound.

Tele lenses need less elements, so ASPH is not as important. However, APO glass is more important to correct for chromatic aberrations. Adding complexity, as well.

Both 50 Lux and 90 cron ASPH have APO elements.

Roland.

 

[dcsang]

Thanks Roland,

I just wondered about it because I see the costs for brand new ASPH lenses and think "jeez, surely it can't be THAT much better than what I've already got can it??"

Cheers,
Dave

 

[ItsReallyDarren]

I see "aspherical" today (even though its been out for a while) to "T* coating" in the mid to late 30's. A flow in optical design that brings incremental improvements and big marketing campaigns.

Not to doubt the improvements of asperical lenses, but more of the question "were non asperical lenses that bad?" Going through Raid's lens tests is the equivalent of taking a cold shower when I feel my current lenses are not up to snuff.

 

[Beemermark]

The difference between the last version Summilux and the newest ASPH Summilux is night and day.

 

[Sonnar2]

The last version Summilux's early 1960's design makes this no wonder 🙂

 

[Juan Valdenebro]

It's easier to make lenses with the form of a fragment of a perfect sphere, so a not perfectly spherical surface lens is more expensive to produce...

Cheers,

Juan

 

[Mackinaw]

The difference between the last version Summilux and the newest ASPH Summilux is night and day.

Likewise with my old Canon FD 55mm F1.2 aspherical. Much, much better than the non-aspherical version.

Jim B.

 

[ndnik]

Is it a more expensive manufacturing method?
Is it merely a reason to charge more (i.e. more profit for putting in ASPH elements)?

Aspherical just means that at least one of the lens surfaces is not spherical. It does not say what its actual shape is. Depending on how the shape differs from spherical (in increasing complexity: just a conic surface, a low-order polynomial, a higher-order polynomial ...) the manufacturing costs could be much higher than for a spherical lens. The reason lies not only with the tooling for grinding (or molding) and polishing the lens, but especially in testing the lens to see whether the surface has reached its specified shape. It's easy to test a spherical surface, and the test is the same for any focal length (a nulling interferometer will do). For aspheres, each surface requires a unique test setup that is much more complicated with unique tooling and evaluation equipment, usually done holographically.

It is true that conventional wisdom says that one aspherical surface replaces two spherical ones in lens design. But some abberations can only be reasonably corrected by ashpherical elements. A spherical design with the same amount of correction would be much larger and expensive.

- N.

 

[Sonnar Brian]

Optical engineers dreamed of aspherics decades before the ability to manufacture them was available. And the first was made in 1955, the Elgeet 12mm f/1.2 Cine Navitar Wide.

 

[charjohncarter]

Optical engineers dreamed of aspherics decades before the ability to manufacture them was available. And the first was made in 1955, the Elgeet 12mm f/1.2 Cine Navitar Wide.

I'm not big on 35mm (format) but (I love them on vacation, which I'm constantly on) I love the wide lenses; so more power to them if they can produce something close. I like my 55mm (Pentax 6x7) and thank the guys that produced it.

 

[35mmdelux]

The difference between the last version Summilux and the newest ASPH Summilux is night and day.

....to the professional this is vital.

 

[Roger Hicks]

Telescope mirrors have been aspheric for decades. They're MUCH more difficult to grind and (as noted) to test, but they really do offer big advantages in correction at a single surface. But as well as ground aspherics there are also moulded glass aspherics (normally only small surfaces) and compound aspherics, which are plastic aspherics moulded onto glass. There has long been some dispute about the durability of compound aspherics but I don't know if it's well founded, out of date or simply blind prejudice.

Cheers,

R.

 

[blue4130]

....to the professional this is vital.

I am a professional and this means nothing to me. I am fairly certain that I make just as much money with my non-asph lenses as I do with them.

 

[varjag]

Zeiss introduced designs with aspherical elements in mid-1930s. Not in consumer products though.

 

[Doug]

...I like my 55mm (Pentax 6x7) and thank the guys that produced it.

So do I... and there's a distinction in the naming... If yours is a 55/4 "Pentax 6x7" then it has 9 elements in 8 groups, and an angle of view of 77 degrees diagonal. OTOH, if the designation is "Pentax 67" it's a different lens with 8 elements in 7 groups and an angle of view of 78 degrees.

The latter one was introduced in 1986 after the previous one was on the market 7 years.

Pentax doesn't always mention that a lens contains an aspheric element, but here their reducing the number of elements in the newer lens raises a suspicion it was done by introducing an aspheric surface. 🙂

 

[antiquark]

Spherical lenses are far easier to grind, using a technique that's been in use for hundreds of years. You can see the spherical grinding in action at this youtube vid:

http://www.youtube.com/watch?v=X7_wL0ZZi6k

Aspherics can't rely on that, they have to use a variety of different techniques to make a lens with a special non-spherical shape.

So yeah, they cost more because they're harder to make.

 

[f16sunshine]

So do I... and there's a distinction in the naming... If yours is a 55/4 "Pentax 6x7" then it has 9 elements in 8 groups, and an angle of view of 77 degrees diagonal. OTOH, if the designation is "Pentax 67" it's a different lens with 8 elements in 7 groups and an angle of view of 78 degrees.

The latter one was introduced in 1986 after the previous one was on the market 7 years.

Pentax doesn't always mention that a lens contains an aspheric element, but here their reducing the number of elements in the newer lens raises a suspicion it was done by introducing an aspheric surface. 🙂

Thanks Doug that is interesting to ponder.
I never owned the f4/55mm but did own and love the older f3.5/55mm. Those big Takumar lenses are simply fantastic and a great work out to use as well 😛

 

[antiquark]

I've got lens history on the brain now... here's a book on the first aspherics:

http://books.google.com/books?id=oA...uygens lens making&pg=PP1#v=onepage&q&f=false

Back in the 1600's, the production of a lens with a hyperbolic shape had become the holy grail for lensmakers. Descartes himself was working on an aspherical grinding machine. (Yes, the same guy who said "I think, therefore I am.")

 

[Roger Hicks]

I am a professional and this means nothing to me. I am fairly certain that I make just as much money with my non-asph lenses as I do with them.

Dear Vance,

Yes, this puzzled me too. I took it as ironic. Perhaps it depends on what you shoot, though I find it hard to imagine any field of photography where it matters whether you use ASPH or non-ASPH lenses on a Leica. Or indeed any other camera. Yes, there are good and bad lenses, but Leica non-ASPH still qualify as good for any application I can think of.

Then again, any lens is good for the right application. I'd back a Thambar against the latest ASPH 90mm, if it's used for the right application.

Cheers,

R.