Used Cooke 10.4-52mm T2.8 S16 - damages or cleaning residues?

July 2, 2013

Dear community,

it would be very kind of you, if you could give me a short advice concerning a used Cooke 10.4-52mm T2.8 S16 lens which has been bought by a friend of mine recently. This friend isn't a member of this forum and asked me for my opinion - but I'm stumped.

He noticed two unusual things:

1. A thin line on (or in) an inner optical element which is clearly visible only at a certain light incidence/when the sunlight shines on it. Therefore I don't think it is fungus, but maybe a separation of the coating or even a thin crack. The vendor said it is a cleaning residue and there's no need to worry - is he right? What do you think?

Please take a look at the linked pictures:

http://s1.directupload.net/file/d/3304/zqsz5g79_jpg.htm

http://s14.directupload.net/file/d/3304/956f7p6r_jpg.htm

2. He also noticed some tiny spots on the rear optical element which get visible under light as well. The vendor said once again this is nothing but a cleaning residue, nothing to worry about. Is this the case? Did maybe some cleaning agent slightly damage the coating or is this fungus?

Please take a look at the linked pictures:

http://s1.directupload.net/file/d/3304/g5tz9jwo_jpg.htm

I'm wondering whether these phenomenons are totally normal for an old lens or whether my friend should seriously consider to return the lens because of possible flaws to the image caused by the two mentioned peculiarities.

Unfortunately, my friend couldn't make any test shots yet because his camera doesn't work :P

I would be glad if you could post your opinion in terms of these pictures. This would really be a great help which my friend and I would appreciate a lot. Thank you very much in advance!

Greetings from Germany,

Robert

Robert Rif · July 18, 2013

1. This could be glue or something stuck on the lens. It's not easy to get a crack looking like that.

2. This could be cleaning residue, or it could be some light damage to the coating. I've got a Taylor-Hobson with quite a lot of damage to the coating, both front and rear lens. The rear lens look similar to this but much worse. I don't think it will affect the image in your case.