Plastic vs glass

[zntgrg]

Hi, some days ago i had a little discussion with my father regarding photographic lens: he's an old Zenit/Praktica/M42 fanboy and says that older german and russian lenses are far better than japanese ones 'cause the latter have plastic lenses rhater than real glass...I can second this, 'cause actually i use those lenses and i love them.

Then i heard also that many jap manufacturers [above all, Nikon] often mix glass and plastic elements, and mainly beause some corrective lenses have complex shapes too difficult to manufacture with glass.

then i heard that a strange little company called HOYA [] sells glass to Pentax.

I really like to know if this family rumors are true [my father is usually right, but also a bit exaggerated in his statements] and how to know what elements are glass and what are plastic, say for example, in the 18-55.

Just for say next time: "yes, maybe Nikon, but not Pentax...true glass only here!"
Thank you very much in advance

[pentagor]

For 18-55 I can say for sure it is a plastic lense. As far as I know Canon's L series is all glass. You notice it by it's weight..
What is better? Hmmm, it is a discusibble topic. Pros would say, glass of course. But for me: it doesn't really mather as long as I'm satisfied with the quality of pictures.

[roentarre]

Originally Posted by zntgrg

he's an old Zenit/Praktica/M42 fanboy and says that older german and russian lenses are far better than japanese ones 'cause the latter have plastic lenses rhater than real glass...I can second this, 'cause actually i use those lenses and i love them.

I heard that all the time.

This is like the way Canikon people criticise sigma products as being the worst quality lenses possible on earth.

This is also like a lot of film photographers criticising digital users not stopping aperture down enough like f22 without knowing diffraction etc.

There are so many specialty lenses available in canon and nikon mount where other brands just could not look up to: Nikon 14-24/2.8 zoom, Canon 1200mm, MPE 65mm 1X-5X macro etc.

Pentax lenses, I thought, were imitations of Voigtlander, Leica or Zeiss in the older times, costing a lot less than these german glasses.

[blende8]

The asphercial elements in all newer Pentax lenses are made of plastic, glued on glas.
There are reports that this element is able to yellow (FA* 24).

[Lowell Goudge]

whether plastic is better than glass will never be answered fully. It is all a question of cost, optical quality stability etc.

Lens materials are selected first for the optical requirements, if 2 different materials meet the optical requirements, then the easiest to produce within the required tolorances would be selected.

whether this is glass or plastic, if it remains stable over a long period, personally I don't care.

[kb244]

Normally when I hear of people saying plastic they are talking about the build quality of the lens, such as plastic lens mount, or plastic body construction, and so forth, while the glass is well ... glass. They just might not put on an extra coating, or use florite as an element of the glass and such to help against diffration.

But I don't think I ever heard of the actual lens elements being made of plastic unless we're talking an early holga.

Though my co-workers who are more experienced in the matter tends to agree with you about plastic-on-glass lens.

[wlachan]

Originally Posted by zntgrg

Then i heard also that many jap manufacturers [above all, Nikon] often mix glass and plastic elements, and mainly beause some corrective lenses have complex shapes too difficult to manufacture with glass.

The process was developed by Minolta as I remember. It is called hybrid aspherical lens which basically means the glass element was being molded in a resin element. The majority of AL lenses are being made this way, not just Nikon. The only Pentax lenses with glass AL I am aware of include the M42 15/3.5, K15/3.5 (earlier version) and the FA31/1.8 Limited. But the FA31 has molded glass AL (higher quality than hybrid aspherical but this method is possible for small size only), while the 15/3.5 have polished AL which is much more expensive to produce as the yield rate is too low. Even the FA*24/2 and FA35/2 have only resin AL.