Haze... What is it?

Jamie Pillers

Jamie Pillers

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For years now I've been reading about lens haze. I just realized that I don't really know what it is. Is it fairy dust? Remains of the big bang? What is it?

And, seriously, can it easily be removed by a lens repair person? If so, how is that done?

When I look through a lens I'm considering buying, is "some" haze acceptable (i.e.: won't really affect image quality)?
 
I always understood it was caused by evaporation of lubricants leaving a coating on the glass and is fairly easily removed with cleaning. I prefer zero haze in a lens whatever it may be ... the difference in the performance of my 35mm Summaron after I had it cleaned was amazing! 🙂
 
On a sunny day when I wash my windshield when driving, it can be impossible to see when the fluid covers the glass in an even film before the wipers finally clear it off. It's most obnoxious when the sun is directly overhead, causing the entire windshield to flare in a blinding panel of light. At other times, it merely reduces my ability to see details through the glass. The reason I'm cleaning the glass in the first place is the bugs and dirt make it hard to see.

The famed "Leica glow" is a result of such haze, as well as "cleaning marks." I think most would say that image quality *is* affected. It induces flare that otherwise wouldn't occur. The lenses are sharp when clean and clear, which is why the "glow" is kind of appealing - it's a sharp image surrounded by a slight flare. A blurry image surrounded by haze is not so appealing 🙂

I'd avoid a hazy lens unless the price plus a professional cleaning is acceptable. Or you just like the look in pictures. You can easily find another lens that has been serviced. The attractive price will account for the haze. There's nothing wrong with picking up a hazy lens just for fun, but i wouldn't pay top dollar for it.

JMHO.
 
I was told years ago that haze in Canon R/F lenses was caused by a phosphorous compound in the focusing mount grease, as Keith says, evaporating and settling on the glass. In severe cases this compound can attack the coating and the glass, although I have only seen this happen (twice) on 3.5/100 lenses that I happen to own. Makes them work like an ultra-Thambar.
And this haze in Canon lenses only seems to settle on the forward facing surface of the element just behind the aperture. Can anyone explain this?
I had to polish this coating off a 2.8/28 Canon before I could use it, and colour rendition, especially red, is not as good as my other Canon wides.
 
For the root-cause, like Charles and Keith said, Jamie. Sometimes haze can also be caused by defects in the cement that keeps elements together (this last one is expensive to fix).

Generally the more forward in the lens defects are (coating marks, scratches, very slight haze, etc) the less optical impact it has.

Haze can be cleaned in most cases, unless the coating/glass have been attacked, or the coating is so soft, that cleaning an element might destroy it (like in old Leitz lenses).

One thing that puzzled me in the past, is that when you look from behind through a lens with a light source in front of it, the longer the lens, the more "visible" even the slightest haze on the rear elements will be. In a wide angle lens, haze is more difficult to detect.

Along those lines, Charles, I think the two surfaces behind and in front of the aperture are most easily affected, since lubricant enters the optics via the aperture, typically. But I think they are more "visible" on the element behind the aperture.

Best,

Roland.
 
Fogging

Mr. Horst Braun, the Manager of the Leica repair department states:
"the special glasses with high refractive index which were used, where unfortunately prone to corrosive damage due to the glass components absorption of moisture. Only later with the availability of new anti-reflective coatings was it possible to eliminate this problem. I still do not believe, that lubricants should be the cause for fogging, because also some internal lenses where affected which never could possibly come into contact with lubricants. I suspect, that the reason why Nikon and Canon did not have this problem at the time was probably due to the fact that they used less sensitive glasses in their objectives."
(C)Stephen Gandy/CameraQuest
​
http://www.cameraquest.com/mlenses.htm
 
Jamie, you might contact ICT camera and see if they clean lenses. I haven't had anything done by them, but they worked on the M3 I picked up locally.
 
Jamie Pillers said:
And, seriously, can it easily be removed by a lens repair person?

When I look through a lens I'm considering buying, is "some" haze acceptable (i.e.: won't really affect image quality)?
Click to expand...
Dear Jamie,

Para 1: Almost invariably, yes.

Para 2: Haze will ALWAYS affect image quality (lower contrast = lower resolution in real terms).

Cheers,

R.
 
I have seen some Canon lenses with a type of "haze" which cannot be cleaned, at least without badly scratching the glass. Many camera shop owners who sell something or ebay sellers will continue to tell that "the haze can be cleaned" and some buyers will keep believing, though. If it's easy, why, as professional camera shops, they don't clean it before selling??

IMHO Mr.Braun of Leica is right in his explanation for hazing. It would explain why so many later (black) series Canon 50/1.8 are badly hazed and the older, chrome ones (designed with older glass) are clear as a bell. He is, however, not right that Nikon or Canon lenses don't made use of high-refractive glass types. Their patent writings of the late 50's show clearly the opposite.
 
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I've had very old lenses with haze that probably had no lubricants to evaporate, and the haze was most likely caused by decades of exposure to environmental pollutants, dust, and such, though evaporated lubricants may indeed be a cause of haze where they are present. The lenses just needed to be disassembled and given an ordinary cleaning and were fine afterward. This is just normal repair work.
 
I'd like a clarification of the difference between haze and fog. Could it be that haze is a deposit that can be cleaned, as Keith wrote about; while fog might be a permanent change in the glass, as suggested in the Stephen gandy quote above? That's what I'm getting as I read these posts.
 
If you live in a cold climate, it likely that repeated cold to warm changes may eventually cause a film to build up on the inner elements, since dust, dirt, and particulate matter in the air may be attracted and held in the condensate.
 
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