Nitrogen Filled Lenses - Why Not?

Started Nov 20, 2008 | Discussions
I Beam Veteran Member • Posts: 3,407
Nitrogen Filled Lenses - Why Not?

Good quality binoculars and scopes are usually filled with nitrogen. As far as I know no camera lenses are nitrogen filled. Some pro lenses have dust and waterproof rubber seals but but these are at the mount only. Nitrogen would make a lens waterproof, dust proof and mould proof.

I realise that a lens would need to have internal focussing and that it should not change length when zooming. So why are some of the zooms such as the 70-200VR and pro level primes not nitrogen filled?

Regards

Paul

Nikko aus London Senior Member • Posts: 1,141
Re: Nitrogen Filled Lenses - Why Not?

It leaks out.

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Genix Senior Member • Posts: 1,444
Re: Nitrogen Filled Lenses - Why Not?

Not to mention that the refractive index inside the lens changes.
Binoculars have to be "close enough". Lens don't have that luxury.

maljo@inreach.com Veteran Member • Posts: 7,660
Air is 80% Nitrogen

100% Nitrogen gets rid of the oxygen.
Is oxygen a problem for lenses?

maljo

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parisphotog Senior Member • Posts: 2,074
Re: Nitrogen Filled Lenses - Why Not?

Did you mail Nikon and ask them?

I Beam wrote:

Good quality binoculars and scopes are usually filled with nitrogen.
As far as I know no camera lenses are nitrogen filled. Some pro
lenses have dust and waterproof rubber seals but but these are at
the mount only. Nitrogen would make a lens waterproof, dust proof and
mould proof.

I realise that a lens would need to have internal focussing and that
it should not change length when zooming. So why are some of the
zooms such as the 70-200VR and pro level primes not nitrogen filled?

Regards

Paul

David Rosser
David Rosser Veteran Member • Posts: 3,475
Re: Nitrogen Filled Lenses - Why Not?

Nikko aus London wrote:

It leaks out.

Hasn't leaked out of my Leica Scope.
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David Rosser
David Rosser Veteran Member • Posts: 3,475
Re: Air is 80% Nitrogen

maljo@inreach.com wrote:

100% Nitrogen gets rid of the oxygen.
Is oxygen a problem for lenses?

Nitrogen is inert, oxygen reacts with all sorts of things (and yes even with Nitrogen to form Nitrous Oxide but only at the very high - 2000K - temperatures you get in the primary zone of a jet engine combustion chamber), far better to eliminate internal corrosion posibilities by not having any oxygen.

maljo

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David Rosser
David Rosser Veteran Member • Posts: 3,475
Re: Nitrogen Filled Lenses - Why Not?

Genix wrote:

Not to mention that the refractive index inside the lens changes.
Binoculars have to be "close enough". Lens don't have that luxury.

Don't see what you are getting at surely refractive index between known nitrogen lens surface interface is going to be as consistent as between air and lens.
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String
String Senior Member • Posts: 2,060
Re: Nitrogen Filled Lenses - Why Not?

Its my understanding (and I could be completely wrong here) that any zoom lens still needs to have a "vent". As the zoom mechanism is moving, its drawing air into the lens/letting air out of the lens so the only lens you could do this with would have to be a prime.

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Genix Senior Member • Posts: 1,444
Re: Nitrogen Filled Lenses - Why Not?

David Rosser wrote:

Genix wrote:

Not to mention that the refractive index inside the lens changes.
Binoculars have to be "close enough". Lens don't have that luxury.

Don't see what you are getting at surely refractive index between
known nitrogen lens surface interface is going to be as consistent as
between air and lens.

It is - however, unless you seal against leakage, over time air (78/21/1
N,O,other stuff) will replace the N in the cylinder, changing the refractive
index. I don't want to pay the extra for the seals, when what we have
works now.

Bob GB Senior Member • Posts: 1,815
Re: Nitrogen Filled Lenses - Why Not?

The reason is it is not feasible. In a binocular, the construction is simple enough so it can be made relatively gas tight. For a camera lens, this is not possible to achieve. Most camera lenses are far to complicated to make gas tight, particularly for zoom lenses. There are so many moving parts and internal volumes that changes size that it would be prohibitively expensive and partly impossible to make everything air tight. In addition, I would expect the resulting frictions with a number of o-rings to be excessive. The important part of filling with nitrogen, is that they get rid of moist, so read: dry nitrogen.

And no, the refractive index will not change when altering the internal gas mixture.

David Rosser
David Rosser Veteran Member • Posts: 3,475
Re: Nitrogen Filled Lenses - Why Not?

String wrote:

Its my understanding (and I could be completely wrong here) that any
zoom lens still needs to have a "vent". As the zoom mechanism is
moving, its drawing air into the lens/letting air out of the lens so
the only lens you could do this with would have to be a prime.

I think you are right here as Scopes and bins are fixed focal length devices - all the zooming in variable magnification scopes takes place in the (interchangable) eyepiece.

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James Sherman
James Sherman Senior Member • Posts: 2,480
Re: Nitrogen Filled Lenses - Why Not?

With lenses that don't grow while focussing all they need is internal venting from one space to another within the lens to prevent turning them into "optical shock absorbers". But I agree that over time, due to zoom ring movement and focus ring movement they'd leak. No such thing as a perfect seal on a moving object (at any affordable price anyhow).

Jim

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Outbacker Regular Member • Posts: 245
Re: Nitrogen Filled Lenses - Why Not?

I Beam wrote:
Nitrogen would make a lens waterproof, dust proof

No, good sealing would do that. What gas it's filled with makes no difference. Dry air is commonly used for some critical optical assemblies, such as laser rangefinders and thermal imagers.

Cheers

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