Is this a coated lens?

Dear Joao,

The old name for coating was 'blooming' and this gives the game away. There is always a faint, coloured 'bloom' on a coated lens.

Modern multicoating is much less clearly coloured than the older single coatings but there is still some colour and the front glass reflects a lot less light than uncoated glass.

A very few, very old lenses can oxidize slightly to create a sort of 'self-coating' effect but this is seldom if ever completely uniform and there may well be a 'rainbow' or 'oil-in-a-puddle' look to the bloom.

Cheers,

R.
 
Roger,

I didn't know about the oxidation of glass causing that rainbow look. both of my Summars display this self coating, but I have a 1937 Schnieder Xenon on a Certo Dollina that is water clear and nearly unmarked. I wonder if the glass formulation has some effect on this.

Steve
 
Roger Hicks said:
Dear Joao,
A very few, very old lenses can oxidize slightly to create a sort of 'self-coating' effect but this is seldom if ever completely uniform and there may well be a 'rainbow' or 'oil-in-a-puddle' look to the bloom.
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Roger,

I have a Meyer-Goertz Trioplan showing exactly such bloom. When I first stripped the camera two years or so ago under the dirt (and it was disgusting - it looked as though it had been kept in a henhouse!) the lens was a very faint purple shade, and I thought I'd destroyed a delicate early coating before I'd realised it was there.

Looking at it recently it now displays a lovely "oily puddle" bloom.

So... When I get a parts shutter for a proper repair job, should I clean this or leave it as it is? If it IS oil I'd like rid of it, but presumably if it is surface oxidation I will wreck the front element trying to remove it?

Hope you can clear those up for me,

Adrian
 
Steve: Yes, the glass type makes an enormous difference: I've seen 100-year-old (and older) lenses water-clear. Maybe storage conditions matter too: I don't know enough to be able to say.

Adrian: Caliope OptiClean (paint on/dry/peel) will remove oil (if that's what it is) but not, I think, oxidation. Either way it won't hurt the lens (at least, it's never harmed anything I've tried, and they guarantee it). That's what I'd go for.

Cheers,

Roger
 
leicasniper said:
Where can you get OptiClean in small quantities? A 500ml bottle is over $800!!!
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Sorry about this. I just checked Caliope's list of suppliers and can't seem to get a good link. Caliope are closed now, but I'd like to know too -- I don't have much left -- and as their website is shown as updated in 2008 I assume they're still in business.

It's a US product repackaged in small quantities by Caliope in the UK; apparently, some members of the US press reckoned it was too hard for US customers to understand the instructions -- a bit harsh, I'd say.

I'll try calling them tomorrow. It takes maybe 1 ml to clean a lens surface...

Cheers,

(and apologies once again)

R.
 
If I may chime in, new Zeiss cleaning kit does a wonderful job, better than everything else I tried.
 
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