A Site for Photographers by Photographers

Community > Forums > Casual Photo Conversations > Fluorite-based APO vs ED vs...

Fluorite-based APO vs ED vs SuperED

Arthur Yeo , Dec 10, 2009; 08:01 p.m.

It appears that using Fluorite-based correction for chromatic aberration (CA) is the most effective and is considered a higher-end solution (if cost is not an issue) than ED or SuperED solutions.

For your reading pleasure ...

If I understand it correctly, the main driving force for not using Fluorite-based solutions in Nikkors is cost. This seems reasonable and consistent with Nikon's corporate policy regarding mass production costs. But, my question is whether the super-teles should be the exception for this policy since they compete directly with Canon's super teles, which certainly use Fluorite, let alone Leica's APO lenses.

What do you guys think? What are your opinions?


    1   |   2   |   3   |   4     Next    Last

Bob Atkins , Dec 10, 2009; 10:48 p.m.

Good enough is good enough. Typically Nikon super-teles are good enough. I don't suppose Nikon photographers particualarly care what their lenses are made of.

Ellis Vener , Dec 10, 2009; 11:00 p.m.

As I recall from a long ago conversation, Cost isn't the reason Nikon decided not to use fluorite elements elements in their high end telephotos. I'm pretty sure Leica and Zeiss don't use Fluorite elements either. My general recollection is that fluorite elements are softer and possibly more heat sensitive - and that last factor may have been the reason Canon started using their distinctive white lens barrels in the first place so they wouldn't heat as much on sunny days.

Bob Atkins , Dec 11, 2009; 12:55 a.m.

Maybe Nikon/Zeiss didn't have a choice. Back when fluorite elements first started to be used Canon had their own process for growing crystals large enough and pure enough to make the elements out of. Canon also fabricated all their own optics so once they had the material they could make the lenses. Not sure Nikon/Zeiss could have found a commercial source of the material even if they wanted to fabricate their own fluorite elements. Then there's NIH (Not Invented Here) which might have been a factor in not following Canon (though it doesn't seem to have stopped Nikon using USM motors and Optical stabilization!).

Fluorite is somewhat more themally sensitive and softer than most optical glasses, but as far as I know that's never been an issue with the Canon "L" lenses that use fluorite elements. I've never heard of a lens that needed that elelment replaced due to aging or environmental damage. I think you can do most of what Fluorite does if you use two "special" glass elements. Modern exotic glasses are available now that didn't exist when Canon first introduced fluorite element lenses

Marc Bergman , Dec 11, 2009; 01:22 a.m.

1969 is when Canon came out with their first Fluorite lenses. I first handled one in 1971. I recall they made an allowance in the focus control to go past infinity. They did mention the thermal sensitivity. The lenses were still black. I don't think they came out with the white lenses until 1976.

Leica uses fluorite in it's latest 50mm f/1.4 ASPH. I don't know who makes that for them. I doubt they would ever say if it was a Canon made element.

Edward Ingold , Dec 11, 2009; 08:26 a.m.

Fluorite lenses have been used for at least 100 years, mainly for their transparency to ultraviolet. That's fine for a lab, but fluorite is soft, brittle and the refraction changes dramatically with temperature. Fluorite also has a low dispersion index, which makes its use in long lenses attractive in order to reduce chromatic aberation. Nikon has eschewed fluorite because of its poor mechanical properties, and achieves the same results with low dispersion (ED) glass. Canon chose otherwise.

Michael Dougherty , Dec 11, 2009; 12:45 p.m.

Several decades ago, I purchased Nikkor 400 mm F5.6 P lens that claimed to have a fluorite element. In the manual, it mentioned that the lens would focus past infinity in order to accommodate the expansion of the fluorite element when heating up. I think it is the only Nikon lens ever made with a fluorite lens element. There was no gold ring on the lens barrel. Also, Hoya has developed an ultra low dispersion glass which I believe is used in the Sigma 120-300 F2.8 and 300-800 F5.6 Sigmonster. Nikon uses a similar ULD glass in its 200 F2.

Bob Atkins , Dec 11, 2009; 01:53 p.m.

Fluorite is used not just because it has low dispersion, but it also has anomalous dispersion, meaning dispersion changes more non-linearly with wavelength than silca based glasses. Both of these factors can be used to minimize CA.

As far as I know fluorite is still the best route to the elimination of chromatic aberration, though some of the newer silica based glass formulations are pretty good (and cheaper).

Arthur Yeo , Dec 11, 2009; 02:08 p.m.

Nikon has eschewed fluorite because of its poor mechanical properties, and achieves the same results with low dispersion (ED) glass.

As the saying goes, one fluorite glass element can be replaced by a few ED elements and possibly by one single SuperED element. If using more ED elements can reduce CA is the way to go, have they thought about more aberrations in the n-th tier that are present just by introducing additional elements?
Additionally, isn't the clarity and brightness of fluorite elements, in generally, higher than ED elements.

Arthur Yeo , Dec 11, 2009; 02:26 p.m.

Marc. B said:

Leica uses fluorite in it's latest 50mm f/1.4 ASPH. I don't know who makes that for them. I doubt they would ever say if it was a Canon made element.

I am not so sure if there's a fluorite element in there but there's certainly a very exotic element in that 50mm Summilux ASPH, whose cost is higher than all 7 elements put together from its predecessor lens it replaced.

The source of that element is from Schott (Zeiss).

It's all here ... http://www.imx.nl/photo/leica/lenses/lenses/page57.html

    1   |   2   |   3   |   4     Next    Last

Back to top

Notify me of Responses