What is haze and what causes it?

I've been looking at lenses on eBay from sellers in Japan and I notice a lot of lenses are described with slight haze and sometimes fungus in them, the ones listed with fungus is quite obvious because you can see spiderwebs inside the lens. I know about fungus (I think) but I'm uncertain about the haze. Will haze have an impact on a picture? Will the picture look cloudy? eBay sellers in Japan describe haze as balsam separation. My wife has a friend in Kyoto until the end of September and I can have the seller mail it to her and let her bring it to me when she comes back to Tennessee. I did this a few years ago and purchased a beautiful NIB Sigma 300 f2.8 EX HSM, 1.4EX TC and a lightly Sigma 150 f2.8 EX HSM Macro and imo the lenses are stunning! This time I'm looking at Ultra wide angle fast primes for landscapes and the heavens. I would greatly appreciate your comments.

Why buy bad equipment? You get what you pay for.

Balsam separation is when cemented lens elements, which were held together by balsam, begin to separate due to balsam either drying out or due to melting from heat. In general it causes the lens elements to defocus, lose contrast, and in extreme cases to decenter from each other. Haze has multiple causes and may or may not be cleanable, depending on the cause and extent of damage. Often caused by lunbrcants outgassing onto the interior surface of the lenses, but also sometimes from contaminants in the air or high humidity getting onto the interior surfaces of the lenses and micro water droplets condensing on those surfaces. Haze is usually cleanable, at a high cost, and does cause a loss of contrast. Very minor haze has slight impact on contrast. Some lenses with haze can be self cleaned by knowledgable amateurs with the appropriate tools to open the lenses up. Don't waste your money on items like this unless you also factor in the cost of cleaning and repair.

I have successfully cleaned haze off a few lens elements, but only where the lenses were easy to open up, and few are nowadays. For example it's sometimes possible to unscrew the rear group in one piece, giving access to more surfaces. I had a Nikon AF 35-70 F/2.8 which looked fine, until I noticed that the images lacked contrast. Shining an LED torch through it revealed patches of haze deep inside the lens. I believe this to be between cemented elements, due to some kind of deterioration in the cement, with no chance of removing it. So yes, avoid any lens so described.

 

Balsam separation usually manifests itself differently, with rainbow patterns often around the edge.

Yes haze will affect the results:

"Leica" glow if you like-a it

caused by oil (re)deposit on lenses, and many other causes.

Primes can usually be serviced without too much trouble. Zooms, not so much. I won't work on them at all. Haze can be many things, but it seems like any time I open a lens with some kind of haze, it turns out to have a fungus problem as well. Caught soon enough, fungus can be cleaned, but it rapidly causes permanent damage. IMO, lenses with fungus are worth about $10, because it's such a crap shoot as to whether then can be cleaned up.

I reckon haze is worse than fungus. A few "spiderwebs" are unlikely to affect the image, but an overall haze probably will.

Don't buy any lens that has some problem with haze or fungus. It won't get better, only worse. A small mark on the front element will not affect IQ but a similar mark or chip on the rear element may cause problems at high f stops on wide angle lenses.

Haze has the extremely annoying tendency to develop in inaccessible area of a lens (often between elements in a sealed optical group). This makes many professional repair techs refuse such cleaning jobs, because messing around with sealed optical cells can affect performance after re-assembly, so they can't guarantee their work.

 

If a particular lens isn't rare or expensive, DIY haze cleaning is an option (and sometimes necessary). The all-black Mamiya TLR 55mm/105mm/135mm/180mm lenses have an infuriating magical ability to manifest chalky haze year after year, cleaning after cleaning: if I didn't learn how to carefully separate and re-assemble the cells, I'd never get more than six months use out of them. Its a PITA, but I live with it, and if I screw up most can be replaced for under $100. But I wouldn't attempt DIY with most modern AF lenses, or pricey manual glass like Leica RF.

 

The highly-humid Japanese climate exacerbates issues that might be more minor in other regions: unless the lens is offered at an incredible bargain price, avoid Japan-offered glass with ANY form of internal defect in the description (haze, fungus, etc). It is likely to be a more severe case than you'd find in UK, Canada, Germany. Optics from Japanese resellers described as excellent with no internal flaws noted are usually a safe bet, but any mention of fungus, haze, separation or coating should be considered a huge red flag.