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A lens' internal haze can be a boon or a bust

David Lyga

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Buying cheap zooms, especially the 80 - 200 variety, can be exciting when cheap enough and if you think that cleaning it will be quite easy. However, sometimes one's greed and shortsightedness overcome such positiveness.

Warning: the Pentax FA 28 - 80, f 3.5 - f 4.7, autofocus, has a special allure when it is sold for $5 (recent KEH transaction). Of course, the condition was 'as is', so I have no complaints.

I am used to removing that rear element set in order to make the glass so clean and bright. But one cannot do this if that rear element set is factory sealed, thus impenetrable. It is very frustrating to look at what I have: Pristine body, pristine glass ... except for this problem. What to do? Haze, so easy to clean, but impossible to reach!!!

For the record, I tested it against a lens with 'clean' glass, throughout. The sharpness was equivalent but the contrast was a grade lower with the haze lens. So, I can still use it, albeit at an aperture that is one step larger than designated. Doing that will compromise matters and build up the contrast so that the lens now performs almost, but not quite, as handsomely as it should. Comments? - David Lyga
 
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I've bought quite a few lenses with haze with the intention of cleaning them up and getting a great lens at a bargain. My experience tells me this works great with primes, but don't attempt it on zoom lenses. Zoom lenses can be a bear to get back together. And sometimes what looks like haze that's easy to reach, is actually haze throughout.

My advice, find out how it's factory sealed. Sometimes it's just a hidden set screw. Sometimes it's adhesive. Both can be dealt with. Open it up from the other end if you have to. Maybe you'll get lucky and fix it. Or maybe you'll get lucky, break the lens beyond repair, and take one of the elements out and build a simple positive meniscus lens to take interesting photos with. In any case, $5 doesn't buy much these days, and I bet you've already gotten $5 worth of entertainment out of it (when compared to the price and quality of today's movies).
 
How brave and creative are you feeling?

- If something was put together, it can be taken apart, and while many will say that you can't un-bake a cake, I've known a few chemists and physicists who got bored and made a damn good try of it anyway...
- If something was set and sealed in a factory, then that suggests that there exists some way to set and seal it in a different environment...

Besides your time, tools, and yourself, what do you really stand to possibly lose by digging into a $5 lens if it doesn't really work the way you want it to in the first place?
 
A few years ago I "found" an image on a proof sheet from 1979. My Spiratone 28mm bleed grease on the rear element of the front cell in the heat of Venice. The image is fantastic, don't know how I missed printing it back then.


 
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I've dismantled quite a few lenses, including various zooms, for a variety of reasons, most often to remove fungus or to free up stuck aperture iris blades. One thing I discovered about internal haze is that, in some cases, even when I was able to reach the affected element, I couldn't remove the haze. It had actually affected the coating. So there is little that can be done in these situations.

I've found that some zooms come apart quite easily, where others tend to be a real bear. It seems that the 80-200 class of zooms usually is the easiest, where the most challenging I've found are the wide-to-short-tele zooms, like a 28-85, for example. And some, you have to be very careful with when you dismantle them -- I'm thinking specifically the Vivitar Series 1 28-90 and 28-105. Unless you're careful, it is quite easy to strip out a series of nylon followers that run in channels in the zoom tubes, that control the spacing of the lens groups as the lens is zoomed in and out. These followers are located by screws that are threaded into thin tubes and it is very easy to strip out these screw holes. If that happens, the lens is junk. I've ruined a couple of these lenses by being a bit too ham fisted when I was dismantling them. Well, one possible repair might can be made, but I've never tried it. Using JB Weld to glue the followers' screws down might work.

I've found Tamron zooms of the short tele to moderate tele class to be fairly easy to disassemble. I've taken apart a few different ones (SP 80-200/2.8, SP 60-300/3.8-5.4, and SP 70-210/3.5 specifically) and successfully reassembled them.
 
Embrace the imperfection, treat it as a gift. A general panacea against the corrosive myths of sharpness, contrast and definition. And keep the sun at your back.
 

I have lots of experience dealing with zooms and let me tell you that the difficulty ranges from 'not so hard' to 'why, why was this constructed in this manner?' I just trashed a cheap Quantaray (28-80) that was so impossible to access that I finally gave up, even though the glass was truly pristine (the aperture needed a simple removal of oil but I could not, for the life of me, access it.)
 

Well and accurately said, The 80-200 are usually the easiest. One thing to note, especially on those long zooms: there are usually three or four large screws surrounding the midpoint of these lenses and, if you remove them (sometimes they are even GLUED IN THOUGH!) you will be able to separate the lens in half and can thus gain easy access to the elements and aperture blades. But, as you rightly said, those damn medium zooms, like the 28-80 or 35-80 can be next to impossible.

Factory sealed rear element sets cannot be unsealed unless you cut through the metal. But when the element is accessible, yes, some haze might not be able to be removed but I will give some advice about that: For some reason skin lotion, left on the elements for about 10 minutes does attenuate the haze a bit. Why, I do not know, but it is worth trying. I have invented new profanity when working on these beasts. My reward is then to work on a prime and come back down to earth. - David Lyga
 
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blockend said:
Embrace the imperfection, treat it as a gift. A general panacea against the corrosive myths of sharpness, contrast and definition. And keep the sun at your back.
Click to expand...
I find what you said both interesting and ameliorative, blockend. Just recently I acquired a Pentax FA 28-80 autofocus and that damn hazy rear element set is factory sealed, thus the haze remains forever intact. However, I tested it and found, to no real surprise, that sharpness is not really affected, but the contrast is one full stop lower and the lens requires one half stop more exposure in order to match the density of a perfect lens.

Your "corrosive myths of sharpness, contrast and definition" I am intuitively tempted to embrace, but can't quite yet, due to my love affair with perfection and precision. But it is, indeed, interesting. I really don't want to use the lens but maybe sometime I will, for your poignant reason.
 
Most autofocus lenses (special the cheap 90th Pentax zooms)are made from too much platistic.
I got a 28mm mechanical Nikon at about 35,- (bought to the right time).
But for such a small price (5 USD) one can be glad that the lens still focus!
I found last week an old pool filter which has the same problem inside (between the glasses)...!

with regards
 
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