I´ve tracked down a Canon Macro Photo Lens 35 mm 1:2.8. This is the lens with an RMS thread, mainly thought to be used with a bellows.
Got it from a dealer whom, in advance, I had asked my elaborate standard questionnaire about glass surfaces, coatings, separation/delamination, aperture blades etc. that I always ask before buying a used lens, at least trying to assure that it is described truthfully.
The answer I got from the dealer in this case was: "The lens is like new".
It came in its original plastic bubble container where it is safely locked in an RMS to FD adapter. Came with an original Canon instruction sheet that seems to be printed in 05/1979. Hence, provided that this is the sheet the lens was delivered with when new, the lens should have been manufactured around that time. The serial-no. engraved on the lens reads 12754.
On first glance the lens looks quite clean and in good condition, but on closer inspection a little "heap" of fine dust can be seen right in the center on an inner element. And on even closer inspection dust and some fibres on different elements inside the lens are visible all over. Let alone when having a look at the lens under my stereomicroscope
: At once my ablutomania arises 
, and I wish to grab for my hoover. (But maybe one should not look at one´s lenses through a stereomicroscope, right?!) 
The following photos may give you some impression of the dust inside. Though, it´s tricky as more or less dust specks ´n fibres flash up depending on the angle of the light and how many surfaces come halfway in focus.
Here the little dust heap OOF in the center
Dust inside shows up under "oblique illumination"
Even more dust shows up depending on the angle of illumination
Now boys, how would you proceed with that lens in such a condition?
From your experience, would you say this is too much dust, and that accordingly it will deteriorate image quality, and hence I should give the lens back and try to find one in better condition?
Or do you think that this amount of dust won´t matter, and that I should keep this lens? The price was 107.- Euro (incl. VAT and shipping).
Do you have any experience what a professional disassembling, cleaning and re-assembling of such a lens would cost? (It´s a 6 element 4 group design.) Or would that be too costly, anyway?
The Canon service that I had sent an e-mail to wasn´t of much help in this respect: They responded that I have to send the lens in first, and then they would tell me how much they are going to charge.
Hoping for your answers that will help me with decision making and thanking you in advance
--Betty
, I should better not try executing such an "operation" myself.
)
