Where have all the bubbles gone?

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DaveW
Posts: 1702
Joined: Fri Aug 04, 2006 4:29 am
Location: Nottingham, UK

Where have all the bubbles gone?

Post by DaveW »

If you were around in the 1970's, or earlier, you may have seen the odd air bubble in some of your lenses elements. I know I had one in my 55mm non-AI Micro Nikkor that took superb close-up's. Some people used to look horrified when you said a quality lens had bubbles in it, but they made little difference to the image and were quite normal.

So if you are buying old quality lenses don't be put off by the odd very small bubble in an element because this is quite normal. Here is a quote on the subject:-

"And, quoting from a 1919 Wollensak catalog, "Air bubbles are not, as is often thought, a defect in photographic lenses. In fact, while they are more apparent in the highest type of lens, they seldom appear in the cheaper grades. Bubbles are caused by the necessity of fusing the optical glass used in making lenses of high quality at a certain temperature, whether all bubbles have risen to the surface or not, in order to maintain certain optical properties. Such bubbles absolutely do not impair the definition or lessen the efficiency of a lens in the slightest degree."

Where have all the bubbles now gone? Has technology managed to remove them, or are different glasses now used?

DaveW

Epidic
Posts: 137
Joined: Fri Aug 04, 2006 10:06 pm
Location: Maine

Post by Epidic »

Unfortunately, they can cause fuzzy points to appear on the image as well as increasing flare, so it is not quite true they are benign. If you have not had that problem, you are lucky.

Why no air bubbles today? Better manufacturing.
Will

DaveW
Posts: 1702
Joined: Fri Aug 04, 2006 4:29 am
Location: Nottingham, UK

Post by DaveW »

Never did, must have been lucky. I suppose it was the height of technology in those days. I believe some cameras even used radioactive substances in their lens elements glasses, and they still make geiger counters click!

http://www.hps.org/publicinformation/ate/q1356.html

DaveW

Epidic
Posts: 137
Joined: Fri Aug 04, 2006 10:06 pm
Location: Maine

Post by Epidic »

AKA: hot lenses. They are flairly easy to spot as the glass yellows over time - although you can bleach the color somewhat with sunlight. Kodak aerial photography lenses are famous as a hot lens. It will expose film if placed on it for serveral hours.

How dangerous are they? I would never buy one as simply modern glass is better anyway. I am not sure I would want radioactive material in my house either - there is problably enough in there slowly killing me anyhow, why add to it.
Will

DaveW
Posts: 1702
Joined: Fri Aug 04, 2006 4:29 am
Location: Nottingham, UK

Post by DaveW »

Thanks Will,

I also got this reply on another site in reply to bubbles in optical glass:-

"Perhaps the answer is in newer technology Dave. The processes used to make fibre optic cable has no doubt advanced the fusing technology process, several layers of different quality (optical clarity and refractive index) are layered together with the best in the middle before the 'log' is stretched to several kilometres long. They wouldn't want any bubbles in that process. The clarity of this super glass in the middle means that if a window of it was a kilometre thick you could see through it as you would a normal window."

Just like making seaside rock with letters in it!

DaveW

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