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Kinoptic 2/25mm vs. Kinoptic 2/25mm
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PostPosted: Tue Jan 19, 2010 4:15 pm    Post subject: Kinoptic 2/25mm vs. Kinoptic 2/25mm Reply with quote

"Pardon me?" you may think, but it is about the effect of age/condition of lenses and the effect on image quality.

I have a c-mount Kinoptik 2/25mm and just got for test a Cameflex (CF for short) version of the very same optic.

Left the results using the CF version, right the c-mount version, both shot under identical conditions just seconds in between using my GH1.





First the full image, then as a second pic a 1:1 zoom into the center of it. Reasons for that massive difference?
The CF version has a scratched rear element and some fogging on the rear element only visible in strong light against a dark background.

So be careful what you buy esp. on ebay and/or ask the right questions early enough!


PostPosted: Thu Jan 21, 2010 4:31 am    Post subject: Reply with quote

Thanks for the post, Klaus.

For me, a scratched or damaged rear element is a no go. A network of tiny scratches (the so called "cleaning marks") on the front is also bad, even if they are barely visible to the naked eye. On the other hand, a big scratch on the front element is usually nothing to worry about, as long as the rest of the lens is fine. A few more links with nice pictures taken through damaged lenses:

http://www.deansphotographica.com/deans_of_idaho/old_stuff_pages/dirtylenstest/dirtylenstest.html

http://www.certo6.com/gallery/planar.html

Cheers!

Abbazz


PostPosted: Thu Jan 21, 2010 9:19 am    Post subject: Reply with quote

Abbazz wrote:
Thanks for the post, Klaus.

For me, a scratched or damaged rear element is a no go. A network of tiny scratches (the so called "cleaning marks") on the front is also bad, even if they are barely visible to the naked eye. On the other hand, a big scratch on the front element is usually nothing to worry about, as long as the rest of the lens is fine. A few more links with nice pictures taken through damaged lenses:

http://www.deansphotographica.com/deans_of_idaho/old_stuff_pages/dirtylenstest/dirtylenstest.html

http://www.certo6.com/gallery/planar.html

Cheers!

Abbazz


Well Sebastien, I am well aware of these rules, but was just curious to see how different that lens would perform, so I got it for testing (since it was also very affordable). It did turn out as I had suspected and wanted to share these results here, before it went back to its owner.

As you say, front lens is rather uncritical (but funny that most people seem to be so funny about that, maybe because it is so easy to see) and forget about the most important part closest to sensor/film, that is the rear element - often exposed mechanically since it protrudes the barrel (depending on lens design) and users sit lenses down to their back end most of the time making damage highly likely. Most wide angle retro designs suffer from that. Then there is the lens inside and fungus webs (often invisible to the unaided eye) [this example here looks crystal clear under normal viewing conditions and needs a strong back light against dark ground to make these fungus traces visible]



or other stuff on the lens surfaces such as fine grease mist condensation (lens kept in a hot place like a car back window) causes massive loss of contrast. The latter can often be professionally cleaned, if it is not "baked" to the lens surface. Lens element separation (of cemented lens elements, which looks like a rainbow developing) is also often seen as massive degradation of lens quality, but it is not in my experience and hardly noticeable in the results.



[faulty rear element with scratches from sitting lens down and debris inside baked on lens surface. Obviously it has been tried to open and clean the lens]