Sonar 120mm 4.5 large format lens dust

DraganB · Jun 3, 2024

hi friends,

I have a nice new lens, despite cleaning there are still pockets of dust in the rear lens group. Do these affect the image quality?

Don_ih · Jun 3, 2024

Are you sure they're not bubbles? I doubt there would be any impact, either way.

numerus · Jun 3, 2024

I also see bubbles. These bubbles were typical for high quality optical glass until the 1960s. I had an Apo-Lanthar that was made in the late 50s that still had these bubbles. I never noticed any effect. The Sonnar is a very nice lens!

JPD · Jun 3, 2024

Yes, it looks like bubbles. The warranty papers used to say that the warranty did not cover bubbles in the glass, because they were unavoidable when manyfacturing some high quality glass types, and that they won't affect the picture quality.

Is it a Contessa-Nettel Sonnar? According to most sources it's a Tessar-type, but I haven't seen one in person.

varg · Jun 8, 2024

Bubbles in the glass or dust particles can´t have an influence to the image quality, this is physically not possible.

Mark J · Jun 8, 2024

Your statement is clrearly untrue - of course a bubble would have an effect if it was big enough. However in most cases bubbles are only small, much smaller than the pupil of light coming through to each image point . That's the key.

Mark J · Jun 8, 2024

Your statement is clrearly untrue - of course a bubble would have an effect if it was big enough. However in most cases bubbles are only small, much smaller than the pupil of light coming through to each image point . That's the key.

varg · Jun 8, 2024

A bubble in the glass has 100 diopter which means that the focus point is inside the bubble, so it has no effect.
You will never find an optical glass with bubbles in sizes which have an influence of the optical quality. This glass will be garbage and never find the way into the lens fabrication.

The case you describe must be a very large bubble, more than 50% of the lens thickness an near to the surface.

Dust particles are without any influence as well. For example, when I get a lens with a chip in the glass or a deep and large scratch I paint it with black colour, This reduces the speed but not the optical system.

Mark J · Jun 8, 2024

You're talking to an optical designer who specifies bubble/inclusion specs, and surface scratch/dig specs every time a lens design is finished.

"The case you describe must be a very large bubble, more than 50% of the lens thickness an near to the surface."
It looks like now you're rowing back on the blanket statement you made above, which is I was responding to.

ic-racer · Jun 8, 2024

Do these affect the image quality?

Do you have the lens in your posession? If so, try it and let us know.

jimjm · Jun 8, 2024

Bubbles like this are not uncommon in older pre-WWII lenses. I would not be concerned about a few of them like you have here. I have several older Wollensak and Cooke lenses with some bubbles, and they've never been a problem.

Whir-Click · Jun 8, 2024

I purchased a lens from around 1915 in its original box and was delighted to find a little manufacturer’s publication on air bubbles tucked inside. A scan is available here.

Marco Gilardetti · Jun 11, 2024

Whir-Click said:
I purchased a lens from around 1915 in its original box and was delighted to find a little manufacturer’s publication on air bubbles tucked inside. A scan is available here.

What a nice little brochure, thanks for sharing!

blee1996 · Jun 11, 2024

Whir-Click said:
I purchased a lens from around 1915 in its original box and was delighted to find a little manufacturer’s publication on air bubbles tucked inside. A scan is available here.

That's good info from a reputable manufacturer! I have a Commercial Ektar 12" and a Carl Zeiss Jena Flektogon 35/2.8, both excellent performers despite some tiny air bubbles in the glass elements.

Nicholas Lindan · Jun 11, 2024

It used to be if a lens didn't have air bubbles it was the sign of an inferior lens made from window glass.

Mark J · Jun 11, 2024

It was typically the early lanthanum crowns that had bubbles. It took a while before formulations and methods were worked out to combat this problem. Hence the association with top-class lenses having some bubbles.

Sonar 120mm 4.5 large format lens dust

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