Film-Tech Forum ARCHIVE: Question abuot the quality of older lenses.

This is topic Question abuot the quality of older lenses. in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=006033

Posted by Erick Akers (Member # 875) on 04-06-2004, 05:54 AM:

Hi Guys and Gals,

Iknow that this subject has been touched upon on occasion,
but because of a conversation I had with Robert at RFS; and the fact that my mother is an optician, I have been tinkering around with older lenses lately!

I am starting to learn that some of those older yellowing paperweights known as B&L as well as the newer, cheaper,
and easier to burn, Skank Whore lenses may not be
as bad as I first thought.

Upon closer examination using lens testing equipment, once unlaminated and cleaned up I am finding that the B&L lenses are performing astonishingly well. I was surprised to find them to be almost comperable to my new ISCO lenses.

Of course; when lab testing, you need to have a control subject, so I purchased a couple of Super Skank Whore lenses on ebay, one good the other bad.

When I say bad,I mean BAD!!! This baby was toast,
we had one Major Halo Burn here.

Even after delaminating the damaged Sankor lens, and removal of the glue a major improvement was made over the untouched sankor!

So what I am asking is,

Is the glue the major objective to overcome when it comes to having a quality image from an older or a newer, cheaper laminated lens?

In all cases so far under examination, I am finding that the actual lens coatings have not been damaged by removal of the glue, but they can be removed by the dip used to re dye glasses.

BTW: The sankor lenses still have a slightly green tint to them, but not as bad after glue removal.

All opinions are welcome!

For all who were curious, I was able to remove the glue by using a vegetable steamer. I tried the freezer method but ended up cracking an element.

Have fun!!!

Erick

Posted by Mark Gulbrandsen (Member # 72) on 04-06-2004, 08:05 AM:

Erik,
A good quality lens cement of the Balsam type is VERY good optically speaking but is heat sensitive. Many of the finest lenses in the world were made with this type of cement including your B&L's and many photographic lenses of extremely high quality. What matters formost in lens making is top notch quality control in all aspects of producing the elements. This is why your B&L's all look good and the Sankors are touch and go. What you will find is that the B&L's while sharp just do not have the contrast ratio ability that some of the Sankors do. The later Sanks have multicoating. But the things I've noticed about the Sanks is that the trade off for good contrast is resolution and flatness of focus. They suck on that department and are VERY inconsistant. We have had an old Kolmorgens elements multicoated and you would probably be amazed at how good it can look! The disadvantages of cemented elements still remains though vs. new designs that are air spaced.

Also if you are wanting to have meaningful disscussions with very knowledgable optical folk you should go to the next years Showest where you can talk to people like Glenn Bergren, and other engineers that are there from ISCO, and Schneider optics. I also ran into the President of Optiform and had some very interesting conversations with him regarding reflectors......

Mark

Posted by Gordon McLeod (Member # 33) on 04-06-2004, 09:37 AM:

I blieve that the slight green tint in lens is from Boron that is used to make the glass heat resistant (Boro-Silicate Glass)