Recently a number of lenses have been presented here for overhaul. After they had been cleaned a large number of surface defects became evident which were not present when they were purchased by the owner. Upon researching the matter on the Internet several sources of information which completely described the processes being used by unscrupulous people to “improve” lenses for sale were found. These are being presented here for you to study without having to spend time searching for them.
I believe that the the owner of a lens has every right to do whatever he wants to do with it. But when it comes time to sell the lens it is necessary to completely disclose everything that has been done to it which a typical prospective owner cannot see with his own eyes and this definitely included lens oiling, repolishing or the use of “scratch removal” paint or wax. Oiling is a temporary solution to a permanent problem which changes the lens so that only the most expensive and difficult solution is available. Painting the front element of a scratched lens with lens scratch removal paint is pure fraud. It is fraud because it doesn’t work. All that is accomplished with the application of lens surface paint is to make the lens look better. The actual effect of transparent lens paint in most cases is to make the lens perform badly when a couple of small scratches would actually have no photographic effect.
Repolishing ruins a lens and is about the same kind of fraud as the use of scratch removal paint.
My advice is that before anyone purchases a Zeiss-Opton or Carl Zeiss marked 50mm 1.5 Sonnar lens a lifetime refund agreement should be obtained from the seller which certifies the lens not been repolished, oiled or scratch minimized with lens paint.
A: Yes, they are.
This is a link to an Internet chat group discussing the use of penetrating oil WD-40 to correct separated Sonnars in 2005: Lens Oiling
The Sonnar lens is uniquely susceptible to lens oiling. The reason for this is that in the late 1960’s and up until the end of Contarex lens production in 1974 Zeiss used an experimental epoxy lens adhesive to cement multiple lens elements together. The problem with using epoxy as a lens cement is that it just continues to harden with time and to shrink very slightly. As it hardens and shrinks it will separate from the part of the lens assembly where the curvature is greatest. This is why a separated Sonnar will always show separation from the edges. The problem is there is no solvent for fully cured expoxy. Epoxy essentially becomes one single molecule with time, and it contains no fillers or other weak points a solvent can attack. The only chemicals I have found that are capable of dissolving the epoxy also attack the lens glass, and this renders them useless. High temperatures above 300oC will melt the epoxy and allow lenses to be separated. But the coatings evaporate from the lenses at this temperature with the result that lenses separated at high temperature must be re polished and recoated which is very expensive and for the 50mm f1.5 Sonnar, the cost greatly exceeds the current market price of an un separated Sonnar.
Oiling a separated lens element is a temporary solution that makes the original problem much more difficult to correct. All petroleum based oils have the property of spreading from where they are originally applied. The oil which is applied to a separated lens will inevitably spread out from the very thin area of separation and will cover the entire lens. The oil that was pulled into the area of separation by capillary action will always remain as a thin film inside the area of separation even when most of it has spread out to cover the entire lens surface. This residual oil cannot ever be completely removed and it will interfere with any other method of permanent separation correction leaving only high temperature separation as the only remaining alternative. The problem with high temperature separation is that it is not clean or complete. Expoxy residue remains on the lens surfaces and this residue must be removed by abrasive which necessitates the lens be “repolished” so that it will look good enough to sell when it has been re cemented.
When a lens is “re polished” it is not the same as Zeiss intended. One of the greatest parts of the lens makers art is the final polishing. Every lens element was taken through a process of abrasive surface removal, starting with the final raw blank of optical glass. With each step the abrasive used became progressively finer. This entire process was calibrated so that when the final polish step was finished the lens would be at the optimum dimensions for the design within a few millionths of an inch. Just how fine was the final polish Zeiss used? Zeiss had, and probably still has, large underground tanks which were isolated from even the slightest vibration. These tanks contained absolutely pure water containing rouge (iron oxide), that had been ground to the final possible fineness. After a period of years the liquid in the tank would be carefully removed from the top. When this liquid was evaporated an incredibly fine abrasive would remain and this is what was used to apply the final polish to Zeiss lenses. This is how very fine the surface of a Zeiss lens is. It is fine within a millionth of an inch. When a lens is “re polished” in a repair shop the degee of fineness of the lens surface that results from re polishing there, when compared to the original Zeiss surface is like comparing a bolder strewn field to the surface of a mirror. Basically, a Zeiss lens that has been re polished is no longer a Zeiss lens; it has been turned into ordinary junk.
A: Yes, they are
This is a link to a web site where lens scratch removal paint was tested under professional laboratory conditions: Lens Paint Testing
The essential thing to understand about liquid lens scratch removal products is that all they are is transparent paint. The proposition that the application of transparent paint to a scratched lens will improve its performance can easily be tested by applying some clear plastic varnish to a window pane. Once the paint dries you will see for yourself just how improved the window is. The same applies to lenses that are painted. The conclusion is that there can be only one reason to apply scratch removal paint to a lens and this is to make it look better so that it will sell at a higher price than its actual condition deserves.
The fact that a lens without visible surface scratches is far more valuable than one with some scratches is undisputed. No one wants a pitted or scratched up lens. The tremendous variety of lens scratch fixers available on the market make it certain that they are used by fix up artists on lenses that have been sold on Ebay and elsewhere. I have had lenses presented here for overhaul which have very fine looking front surfaces which immediately become disclosed to be pitted and scratched once a drop or two of acetone is applied to the front surface with a cotton swab.