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183 comments on DrumBeat: February 27, 2008

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eric blair on February 27, 2008 - 11:22am Permalink | Subthread | Parent | Comments top

Why would only that lens require lead

Optical properties of leaded glass? Or perhaps the lead makes the glass more shape-able, thus allowing the maker to get the lenses correct.

And my gut was right:

Lead oxide added to the molten glass gives lead crystal a much higher index of refraction than normal glass, and consequently much greater "sparkle".[citation needed] The presence of lead also makes the glass softer and easier to cut.

(Now I'm looking up homemade glass foundries - just what I need - more stuff to consume electricity!)

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Leanan on February 27, 2008 - 11:27am Permalink | Subthread | Parent | Comments top

I don't buy it. That doesn't explain why the 200mm f/1.8 would need lead, but not, say, the 300mm f/2.8.

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eric blair on February 27, 2008 - 11:58am Permalink | Subthread | Parent | Comments top

I do.

Channeling physics of optics from my teen years and my now dead grandpa commenting on how all the good binoculars were made in Germany VS Japan - I have no trouble believing that better manufacturing and knowledge of optics would make the lenses 'better' over time. Better ways to make glass lenses helped drive down the cost and up the quality so my Grandpa's POV was just wrong by the time came I cared about a set of Binoculars.

In the case of the 2 lenses - we do not know the size or the arrangement of the glass elements - therefore one can not say with any kind of authority if the improvements are due to the better manufacturing of the glass elements or changes in the placement or different dopants in the glass.

Optics and the rules about how photons travel are well enough understood that if we know the lens placements and the dopants in the glass, we can calculate the 'betterness' or even how one lens is working VS the other. Finite Element analysis or POV ray tracing are to ways I can think of - based on what I remember of physics of light and such from my misspent youth.

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Leanan on February 27, 2008 - 12:05pm Permalink | Subthread | Parent | Comments top

Forget the lead. Look at the dates. The EU ban started July 2006. Canon stopped manufacturing the lens in question in 1998, and officially announced its retirement in 2001. Lead had nothing to do with it. It was all about low sales.

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DaveMart on February 27, 2008 - 1:53pm Permalink | Subthread | Parent | Comments top

Hmm, actually I expressed myself poorly, and there was more than one lens at issue - I can't remember the details now at this distance in time - the 200/1.8 was the one everyone focussed on.

But the real issue though is that it didn't just affect luxury goods, medical imaging equipment and so on was also affected, where it is really, really nice to be able to see what is happening.

There are probably other fields I am unaware of where it also may have had a major impact.

Now I am not sure if they have been able to work around these problems and get the same standard of performance in all fields as before, but the general point is that bans should be imposed with care, and individual items looked at to assess the impact, rather than just coming out with one size fits all legislation.

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alan on February 27, 2008 - 9:47pm Permalink | Subthread | Parent | Comments top

Chromatic aberration becomes more of a problem as the f-ratio gets smaller.

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183 comments on DrumBeat: February 27, 2008

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