[HYS]

I think that "hybrid aspherical optical elements" dosn't mean automatically worst quality of the lens or of the image or both. It highly depends on design and on the precision of manufacturing.

[pentaxus]

The first hybrid aspheric I knew about was in the Minolta 28-85 zoom in the 80's. I was concerned about durability. I have never seen a delaminated hybrid lens. I don't worry about it now.

[ffking]

On the SRS site the old version is 10 elements in 9 groups, the new one is 6 elements in 5 groups - !!??

[HYS]

On the SRS site the old version is 10 elements in 9 groups, the new one is 6 elements in 5 groups - !!??

Just mistake.

[ffking]

Just mistake.

They got it from the Ricoh Imaging website - obviously flies in the face of their description of what they sat they did, so it is a mistake, but one they should correct!

[Digitalis]

different aspherical element construction. The specification for the new HD version says it's a hybrid element - which isn't the same as the older lens' ground glass element.

I have my doubts the original FA35mm f/2 employed a ground aspheric - The lens literature from pentax, frustratingly, obfuscates the exact technologies they use to produce their lenses by hiding it behind acronyms, or shorthand descriptions devoid of critical detail.


What I do know is that ground aspherics are typically very expensive, and the expense rises exponentially with the element diameter*. Considering the FA35s vignetting and border resolving power (even when stopped down) the geometry of the aspheric isn't able to compensate for astigmatism to the degree necessary - this indicates (to me) that it is (at best) a GMo asperic, there are limits to the degree of curvature an element can have when molded, (thick glass cools slowly, thin glass cools quickly) if the shape is too extreme there will be temperature differentials that will destabilize the glass in a number of ways which will make the element uniquely prone to damage even if annealed correctly.

I believe the hybrid is cheaper to manufacture and is better at controlling aberrations. I don’t really see a down side to it.

Correct. Hybrid aspherics are cheaper to produce: but more labor intensive as there are more components to align and therefore: an elevated chance something will go wrong during assembly**.


Regarding the degree of optical correction a Hybrid aspheric can offer, is distinctly inferior to solid glass aspheric and here's why: The dispersion properties of optical polycarbonate*** aren't as varied or easily manipulated the way glass is so additional compensation is needed, usually in the form of extra corrective optics which can result in a heavier lens - heavier than it would be if a single aspheric of homogeneous materials were employed.

No, a single glass element is better, and ground rather than molded.

Correct. Though IMO from a cost/optical quality perspective, Glass molded aspherics are superior to both hybrid/ground aspherics.

* which is intrinsically linked to lens speed.
** And as someone above mentioned with hybrid asperics: the whole blasted thing can de-laminate rendering the entire lens completely useless. This did happen with older lenses, but is a rare occurrence in modern lenses.
*** Refractive index range of optical grade polycarbonate: 1.580 ~ 1.599. Refractive index range of glass: 1.670 [ Flint ]~ 1.505[Crown ] all measurements obtained at a 558nm wavelength.

[Andrea K]

Having recently pre-ordered the new HD FA35mm f/2, I've just noticed the specifications state that it includes "hybrid aspherical optical elements", whereas the original FA35 f/2 - if I remember correctly - used a (more expensive to produce) ground glass aspherical element. It seems this little detail might have slipped below the radar so far?

I can't say I'm particularly concerned... my "plastic fantastic" DA35 f/2.4 includes a hybrid element, as do several of my other lenses, and I'm perfectly happy with the performance - but it's a surprising (if small) downgrade(?) that might temper the excitement of the upgrades for some folks. As I understand it, hybrid elements may be more susceptible to environmental changes such as humidity and temperature... though "more susceptible" might still mean "irrelevant" in this case (frankly, I'm not qualified to judge). Some world-class lenses include hybrid elements, so I doubt it's a cause for concern...

It's interesting that the glass isn't exactly the same as the FA35/2, though. This suggests that Ricoh might not simply be using up stocks of existing FA35/2 components in the new lens... That in fact, HD FA35/2 is being manufactured from entirely new component stock.

Anyway, this doesn't affect my interest or order at all. I just thought it was an interesting difference

From Ricoh Imaging japan site about the smc-FA 35mm f/2.0 AL:
"[FA 35mm F2 AL] The lens has an optical system using a hybrid aspherical lens and ghostless coating [...] This high-performance lens is the first 35mm F2 lens for 35mm AF SLR cameras which uses aspherical lenses for correcting various types of aberration and providing a sharp image quality with high contrast from the minimum to the infinity end and high resolution up to the edges even when taken in an open aperture state. A ghostless coating is also used to enable shooting of clear images with little ghosting or flare even under backlighting and other adverse conditions. Closeup shooting up to 30cm is also possible with this lens."

[BigMackCam]

I have my doubts the original FA35mm f/2 employed a ground aspheric - The lens literature from pentax, frustratingly, obfuscates the exact technologies they use to produce their lenses by hiding it behind acronyms, or shorthand descriptions devoid of critical detail.


What I do know is that ground aspherics are typically very expensive, and the expense rises exponentially with the element diameter*. Considering the FA35s vignetting and border resolving power (even when stopped down) the geometry of the aspheric isn't able to compensate for astigmatism to the degree necessary - this indicates (to me) that it is (at best) a GMo asperic, there are limits to the degree of curvature an element can have when molded, (thick glass cools slowly, thin glass cools quickly) if the shape is too extreme there will be temperature differentials that will destabilize the glass in a number of ways which will make the element uniquely prone to damage even if annealed correctly.

From Ricoh Imaging japan site about the smc-FA 35mm f/2.0 AL:
"[FA 35mm F2 AL] The lens has an optical system using a hybrid aspherical lens and ghostless coating [...] This high-performance lens is the first 35mm F2 lens for 35mm AF SLR cameras which uses aspherical lenses for correcting various types of aberration and providing a sharp image quality with high contrast from the minimum to the infinity end and high resolution up to the edges even when taken in an open aperture state. A ghostless coating is also used to enable shooting of clear images with little ghosting or flare even under backlighting and other adverse conditions. Closeup shooting up to 30cm is also possible with this lens."

Thank you both

Then I suspect it may be urban legend that the FA35/2 contained a ground glass aspherical element. I've been searching online, and I can only find mention of it in forums, with no obvious source of official information...

[Andrea K]

The smc-FA 31mm f/1,8 AL Limited has a glass molded aspherical lens

[beholder3]

The dispersion properties of optical polycarbonate*** aren't as varied or easily manipulated the way glass is so additional compensation is needed, usually in the form of extra corrective optics which can result in a heavier lens - heavier than it would be if a single aspheric of homogeneous materials were employed.

*** Refractive index range of optical grade polycarbonate: 1.580 ~ 1.599. Refractive index range of glass: 1.670 [ Flint ]~ 1.505[Crown ] all measurements obtained at a 558nm wavelength.

I need to object here. Zeiss for example offers non-glass organic "plastic" lenses for human vision between index ranges from 1.5 to 1.74 (ZEISS Einstärken Individual).
Maybe what you say pertains to exactly optical polycarbonate, but I do not believe a "hybrid" lens is limited to that material.

[clackers]

Correct. Hybrid aspherics are cheaper to produce: but more labor intensive as there are more components to align and therefore: an elevated chance something will go wrong during assembly**.

Very good interview with Motoyuki Ohtake, ex-Nikon, now Sony's head lens designer, on aspherical elements:

Sony raises the bar: We talk with Sony’s top lens designer about what makes their latest lenses so special

[BigMackCam]

Very good interview with Motoyuki Ohtake, ex-Nikon, now Sony's head lens designer, on aspherical elements:

Sony raises the bar: We talk with Sony’s top lens designer about what makes their latest lenses so special

Fascinating article. Thanks for posting that

[nocturnal]

Clackers, I've started reading this article, looks good. This guy has 200 patents to his name, hopefully he owns the patents and not intellectual property of companies. I'd say he got head-hunted?

[Digitalis]

I need to object here. Zeiss for example offers non-glass organic "plastic" lenses for human vision between index ranges from 1.5 to 1.74

The nature of the polymer Zeiss is using for these lenses is unknown. It would be unlikely to be used in lens construction, as the properties of contact lenses and the requirements for bio-compatibility would make them different from what is required from precision optical elements.

Maybe what you say pertains to exactly optical polycarbonate, but I do not believe a "hybrid" lens is limited to that material.

Precisely, Acrylic has an even lower range of R.I. and there are some materials that have wider ranges - but are not used in aspherics due to low thermal stability, or inferior transmittance.

[nocturnal]

So Sony's new asph fabrication developments result in smaller and cheaper lenses. This is where it is at then and I don't like monster lenses if they don't have to be as big or costly.