Thread: The Pentax MX
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Old 04-05-2019   #102
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nickthetasmaniac is offline
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Originally Posted by CMur12 View Post
My understanding is that the 7-element 50mm lens that succeeded the 8-element version was made with special (radioactive; thorium?) glass, which Pentax probably felt offered the same performance with one less element. I'm pretty sure the radioactive glass cost more than the more common glass. I don't see it as Pentax lowering their standards.

- Murray
I'm far from an expert on this (hopefully others will offer their take...) but my reading is that the cost associated with the 8 element wasn't just that it had one more piece of glass, but rather than it had a cememted triplet that was very expensive to manufacture. Every bit of info I've come across agrees that the 7 element was more affordable to produce*.

I don't know the relative cost of thorium vs regular glass, but given that Pentax also used thorium in their cheaper 'kit lens' 55/f1.8, I can't imagine the difference is significant.

*Having said all that, none of the comparisons I've seen between the Super-Tak 7 and 8 elements suggest a notable difference in image quality.
Ricoh GRII | Pentax SV, SP-F, MX & LX | Leica M2 | Olympus Pen F + 35RD | Minolta Autocord | Hasselblad 500cm + SWC/m

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