wideopeniris
Newbie
Having now obtained a second copy of the Canon S Series 100mm F3.5 Lens with milky fog on the middle negative element, I was inspired to finally work out why they are foggy.
My first lens, someone had attacked the element and it had fairly deep scrtaches on as well as the speckely fog. For those unfamiliar, you will see plenty of these lenses advertised for sale with 'fog' or 'haze'. You may be tempted to think 'Oil Haze - an easy clean' but this is not the case. Having tried all solvents and other normal cleaning techniques, the Haze is stubbornly unaltered. The surface appears covered is milky blobs on both faces.
So I took the trouble to put the lens element under a proper microscope to see what was going on.
The dark spots are in fact the original (single) coated surface which has degraded is a fairly disastrous manner. Unlike fungus which starts at a dust spot and then has filaments of surface damage, this effect is everywhere across the lens surface. The coating has degraded due to some chemical attack, possibly from the glass itself or from something trapped in the lens body. A shot nearer the edge of the lens makes this clear:
What we see here is a ring that was underneath the metal mount ring. Here the coating is uniform and largely unaffected. Also you can see clearly that all the marks are formed of a sheet of uniform thickness which is crazed and damaged, probably from chemical attack or failure to adhere correctly in the first place.
Needless to say that this is unrecoverable without (probably very difficult) re-polishing and recoating of the element. Therefore I would advise against picking up these fogged lenses cheap, hoping they will clean up, as the promblem is not reversible, as it might be if it was oil haze. I have two of these - the earlier one is chrome and black, and the later is all black - both have the same basic trouble, although the older one was exacerbated by someone elses less gentle approach.
Anyone think they have a workable and cost effective solution to fixing this problem?
Opions welcomed.. anyone else seen this with other lenses?
My first lens, someone had attacked the element and it had fairly deep scrtaches on as well as the speckely fog. For those unfamiliar, you will see plenty of these lenses advertised for sale with 'fog' or 'haze'. You may be tempted to think 'Oil Haze - an easy clean' but this is not the case. Having tried all solvents and other normal cleaning techniques, the Haze is stubbornly unaltered. The surface appears covered is milky blobs on both faces.
So I took the trouble to put the lens element under a proper microscope to see what was going on.
The dark spots are in fact the original (single) coated surface which has degraded is a fairly disastrous manner. Unlike fungus which starts at a dust spot and then has filaments of surface damage, this effect is everywhere across the lens surface. The coating has degraded due to some chemical attack, possibly from the glass itself or from something trapped in the lens body. A shot nearer the edge of the lens makes this clear:
What we see here is a ring that was underneath the metal mount ring. Here the coating is uniform and largely unaffected. Also you can see clearly that all the marks are formed of a sheet of uniform thickness which is crazed and damaged, probably from chemical attack or failure to adhere correctly in the first place.
Needless to say that this is unrecoverable without (probably very difficult) re-polishing and recoating of the element. Therefore I would advise against picking up these fogged lenses cheap, hoping they will clean up, as the promblem is not reversible, as it might be if it was oil haze. I have two of these - the earlier one is chrome and black, and the later is all black - both have the same basic trouble, although the older one was exacerbated by someone elses less gentle approach.
Anyone think they have a workable and cost effective solution to fixing this problem?
Opions welcomed.. anyone else seen this with other lenses?
ferider
Veteran
Thank you very much for this. Lot's of Canon lenses have this, I've seen it in 100/3.5, 50/1.8, 50/1.5 and 50/1.2, and in more than one sample each.
The 50/1.4, 85/1.8 and 35/2 samples I have seen seem immune to this.
Must be either from lubricant or from the glass itself.
Roland.
The 50/1.4, 85/1.8 and 35/2 samples I have seen seem immune to this.
Must be either from lubricant or from the glass itself.
Roland.
charjohncarter
Veteran
Thanks for this essay. I have a Canon Serenar 35mm f3.5, that has haze (fog). I have been cleaning the elements between uses thinking that it is oil. But maybe I have something like yours as my lens has never been that good.
wideopeniris
Newbie
I guess it goes without saying that if anyone has a damaged 100mm F3.5 where the middle element is OK then I'd be really interested (hoping for the hopeless, I suspect 
)
)
WHICH Canon 100/3.5?
I've only seen this problem on the black versions.
I've only seen this problem on the black versions.
wideopeniris
Newbie
As I said in the OP, I have 2 with the same problem. One is the All Black (Serial 86xxx) and the other is the chrome and black type (serial 65xxx)
The Chrome and black looks identical to Mk II on the Canon Museum site. The All black matches all the other later black lenses with the partly knurled focus ring and all black body and has a more sensible filter size (!)
The Chrome and black looks identical to Mk II on the Canon Museum site. The All black matches all the other later black lenses with the partly knurled focus ring and all black body and has a more sensible filter size (!)
02Pilot
Malcontent
My early chrome-and-black 100/3.5 (#57xxx) is absolutely free of fog. In fact, it was one of the only lenses I've ever purchased that didn't require some sort of cleaning, however minor. Perhaps Canon changed lubricants at some point and the later stuff is the cause of the problem.
hanskerensky
Well-known
Very enlightening !
Thanks for your efforts to publish this !
Thanks for your efforts to publish this !
kuuan
loves old lenses
very interesting, thank you for showing this!
Not giving up I collected 3 all black and one chrome / black version. All of them have at least some haze, even the chrome / black, that can't be just wiped off, though the chrome / black has the least.
I agree that this haze hardly, if at all, can be repaired, and that therefore better to stay away from these lenses. I did polish the most badly effected element, the one of the worst copy, and since anything else hardly had any effect in the end with a tremel tool and Cerium Oxide. That did leave it quite clear, after hours of work. - That it seems to be the coating 'only' that has gone bad is the only good news here, one can remove that, but the performance won't be the same as of a clean copy.
Not giving up I collected 3 all black and one chrome / black version. All of them have at least some haze, even the chrome / black, that can't be just wiped off, though the chrome / black has the least.
I agree that this haze hardly, if at all, can be repaired, and that therefore better to stay away from these lenses. I did polish the most badly effected element, the one of the worst copy, and since anything else hardly had any effect in the end with a tremel tool and Cerium Oxide. That did leave it quite clear, after hours of work. - That it seems to be the coating 'only' that has gone bad is the only good news here, one can remove that, but the performance won't be the same as of a clean copy.