Jump to content
Sign in to follow this  
pgk

So what actually is lens 'haze'?

Recommended Posts

Advertisement (gone after registration)

I've just seen a comment saying that haze is deposition of lens lubricants on the glass surfaces. Whilst this makes sense to an extent, is this the only cause? I doubt it.

 

Some lenses are far more susceptible to haze (and even in certain specific places - the thin Tele-Elmarit suffers from haze on its rear group for example) and I'm well aware that some glass types can suffer from oxidation. This was apparently why many early glasses could not be used in lens making if they were going to have an exposed surface as (especially damp) air exposure would result in oxidation and thus haze.

 

I assume that this is true of coatings too. Originally coatings were caused by chemical changes; like oxidation. This was referred to as blooming on lenses and I believe that it was the discovery of improved transmission of bloomed lenses which led to the development of coatings. Some older coatings have now been on lenses for many decades - half a century or more - so will have had a long time to deteriorate if they are going to do so. And their are some pollutants which can get into the air which may well be corrosive too.

 

Any other ideas?

Share this post


Link to post
Share on other sites

Simple dust is another cause, at least if longer periods of time are considered. Air (and thus dust) flows into and out of the optical system, and tiny dust particles accumulate on the lens surfaces. Over longer periods of time, they form a hazy film.

 

Andy

Share this post


Link to post
Share on other sites

[...] the thin Tele-Elmarit suffers from haze on its rear group for example [...]

 

None of my copies from 1979 and 1987 i must say. Flare is another story.

Share this post


Link to post
Share on other sites

None of my copies from 1979 and 1987 i must say. Flare is another story.

 

I've had one with and two without - I just wonder if Leica either changed to coating or had a coating issue at some point?

Share this post


Link to post
Share on other sites

I've had one with and two without - I just wonder if Leica either changed to coating or had a coating issue at some point?

 

I don't know. My German copy (1987) shows less flare when highlights are into the frame but i've never got any haze issue with it or my Canadian copy (1979) so far.

Share this post


Link to post
Share on other sites

Haze is often said to be lubricant condensing on the lens surface. Could be. I think it is just atmospheric crud that accumulates over time from moisture condensing on elements. Any lens that lives in a very cold climate or hot and humid, and comes in and out of the house will get some condensation. Over time this creates a fog. Some lenses like older Summicrons have high heavy metal content in the glass and this can oxidize, making maters worse, the reason many Summicrons will not clean up. Moral; only by old lenses that lived in a desert climate!

Share this post


Link to post
Share on other sites

I removed some haze from front element of Summar. But Canon 50 1.8 LTM has unremovable inner haze, but not etching.

I guess, it is not always lubricant out gassing on the lens.

Share this post


Link to post
Share on other sites

Mineral glass ports used underwater can haze if not dry when fitted with their neoprene cap. Water is trapped and the glass seems to oxidise as a result. They can be re-polished but the haze is hard and doesn't remove easily. So one reason for hazing could be condensation and subsequent oxidation but I doubt its the only one hence my query.

Share this post


Link to post
Share on other sites

Mineral glass ports used underwater can haze if not dry when fitted with their neoprene cap. Water is trapped and the glass seems to oxidise as a result. They can be re-polished but the haze is hard and doesn't remove easily. So one reason for hazing could be condensation and subsequent oxidation but I doubt its the only one hence my query.

Salt deposit?

Share this post


Link to post
Share on other sites

Haze can be anything that settles out of the air inside the lens onto the inner surfaces of the glass. The lubricants on the aperture and in the focus threads are relatively "available" and easy to vaporize and then resettle onto the glass, but with enough age, other things (dust, salt-air, fungus) can get in and collect on the glass, to the point that they are dense enough to refract the light themselves and spread it around as a "foggy" look to pictures.

 

Lenses are not generally air-tight (some recent lenses have been made more so - e.g. Fuji X teles) since they have to "breath" as they expand and contract while focusing (otherwise you'd be fighting a vacuum when focusing - see: http://www.eoht.info/page/Magdeburg+hemispheres ) Every time you focus an M lens, you are pumping air in and out like a bellows.

 

Even the coatings on the lenses can, if the lens gets warm, theoretically vaporize and then redeposit on the "wrong" glass (since vapor deposition is how they are applied in the first place - heat up the magnesium flouride or whatever you are coating the lens with, in a vacuum, and the MgF vaporizes and redeposits onto the glass as a film.)

 

Some haze just sits on the glass and can be cleaned off - other things like fungus will permanently corrode the glass, requiring either replacement or regrinding of the surface.

 

As to the 90 TE thin, there were two parts to the problem. First, whatever it was that hazed those actually ate into (corroded) the glass. And the two rear elements were installed as a single factory-sealed unit. So IF they got haze, there is no way to remove it or repair it except by replacing the "unit" as a whole - and Leica no longer has any replacement units. > Paperweight.

 

In that line of thought, there are some airborne things that can actually react with the glass chemically and "fog" it - ot may have been (in a less knowledgable era) built right into the lens or glass because they were not recognized as a threat. I don't know if anyone has ever definitively found out what (if anything) was particular to the chemistry of the 90TE to cause its haze problems (only in very early copies). Canadian balsam? Whale-Oil? I've seen them all mentioned.

Share this post


Link to post
Share on other sites

Salt deposit?

 

No - happens with fresh water too - its oxidation. Oxidation of some glass types has been known for a very long time and some glass types have been avoided for optical use as a result.

Share this post


Link to post
Share on other sites

And then there is something calle 'Schneideritis'. It could be described as being like a white powder on the lens inside. Maybe the coating reacts with moisture and forms small islands of residue. 

These Schneiderized hazed lenses still can be very nice. When used in low-contrast situations (overcast sky).

And they give a vintage look when used against a clear sky.

But it can be annoying too when you get a whitish or even blue glare.

 

Photographically I find my M-Rokkor 28  a very interesting lens, even though it has that Schneider-sickness. It is amazing sharp, & does not need coating on the M240 and gives no noticeable fringing. Three examoples from this [hazed] lens with my preferred camera for that lens.

 

example 1 (forum member pete), the lens wide open. No haze to be seen anywhere. 

Pete with his nice hat with a hunter's feather by Albert K., on Flickr

 

example 2

Raise high, the roofbeam by Albert K., on Flickr

 

example 3/4, with blooming high keys

 

 

Share this post


Link to post
Share on other sites

White dots on the Rokkor 28/2.8's innards are not on the lens elements themselves, only on the black coating AFAIK so they should not do haze effect normally. Now my copy is almost free from those dots fortunately. Great little lens indeed, even smaller than the Elmarit 28/2.8 asph. Too bad it triggers 35/135 instead of 28/90 framelines on my M bodies. I wonder if it is possible to mount a Rokkor 90/4's flange on it. I dare not try with my copies as i like much this Rokkor 90/4.

 

 

Share this post


Link to post
Share on other sites

I have an f/3.4 Super-Angulon-M with mild Schneideritis. Its another oddity as it seems to be the internal paint which turns white in specks. I don't think that it has much optical effect. It doesn't seem to be the paint actually flaking off as there are no visible particles, but it is relatively common so I'm sure that someone mush have looked into it and know the cause.

Share this post


Link to post
Share on other sites

IIRC, Schneideritis is the separation of very small particles of paint from the glue on the edges of the affected lens elements.

The particles falling off are really tiny, but the white spots due to the paint loss appear much larger from the outside due to the magnifying effect of the glass.

Therefore, unless you see a lot of white dots or large white areas, it is mostly a cosmetic issue and the effect on IQ is comparable to that of regular dust specks - ie, negligible in practice.

But yes, it does make the lens look unhealthy...

Repainting the edges of the element(s) is a fairly straightforward job for a competent technician, but it involves dismantling the lens, so it really makes sense in conjunction with a full CLA. I have had this done once (on a Prominent Nokton) and the lens does indeed look much better.

Share this post


Link to post
Share on other sites

I had my 28mm ZM lens fall in the water several years back. There was a bit of fog for a few days, that disappeared again and I never noticed any degradation, no haze. I gave it a CLA this spring.

The funny thing is I like the 'signature' of the M-Rokkor more. Fits into a world where you find the SEM. 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...