Glass bubble in Noctilux f0.95?

Started Sep 1, 2013 | Discussions thread
LeitzKameraAktion
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Re: Glass bubble in Noctilux f0.95?
In reply to meagre offerings, Sep 2, 2013

In my experience, it's not common to see air bubbles in a Noctilux. But it does sometimes happen.

Many exotic high refractive index 'Rare Earth' glasses cannot be sufficiently heated to become fully liquid without the special properties of the glass being diminished. This creates the possibility of air bubbles being trapped in the glass as it cools.

The glass used in the Noctilux is among the most exotic found in any lens. It's notoriously sensitive, and takes about a year to cool. It requires very careful handling, and helps explains why Leica can only make small quantites of this lens.

In years past, the presence of a few tiny air bubbles was actually seen as a sign of quality. One way of telling if a lens was made using Rare Earth glass was the presence of bubbles. Since the 1960s, bubbles in the glass have become less and less common as manufacturing techniques have improved. But, it's still difficult to totally eliminate them.

Of greater importance for image quality is the extremely fine 'Nano level' finish Leica apply to the surfaces of their glass. It's one of the things you pay for with the more recent Leica lenses. Unfortunately, you cannot see this with the naked eye!

Here's something from Schott explaining a bit more about optical glass - including a short section on bubbles   http://www.stanford.edu/class/ee347/sglass.pdf

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