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Killing a lens for experimental purposes?
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PostPosted: Sun Oct 18, 2009 8:13 pm    Post subject: Killing a lens for experimental purposes? Reply with quote

Like many of you I have more than my fair share of unsellable Prakticas with Pentacon 50/1.8 lenses. So I thought it would be a nice test to see how the picture quality degrades when the lens will be gradually more mutilated. Let's start with, say, a large coating mark right through the front element, after that a large, deep scratch, ending with a totally smashed front element. After this exercise I will do the same, but this time with the back element. Maybe this will help assuring buyers that not only the minty lenses are worth buying. Wink

Or... will I be banned forever now? Laughing


PostPosted: Sun Oct 18, 2009 8:21 pm    Post subject: Reply with quote

Make sure you capture all of this on video, too. YouTube needs you!


PostPosted: Sun Oct 18, 2009 8:26 pm    Post subject: Reply with quote

ChrisLilley wrote:
Make sure you capture all of this on video, too. YouTube needs you!


LOL, yes, I forgot that we live in the Youtube age now Smile


PostPosted: Sun Oct 18, 2009 8:38 pm    Post subject: Reply with quote

this could be interesting
I found degradation appear with a sample UV filter
Maybe I should try a scratched UV filter
or even better, a UV filter without front element


PostPosted: Sun Oct 18, 2009 8:46 pm    Post subject: Re: Killing a lens for experimental purposes? Reply with quote

Spotmatic wrote:
Or... will I be banned forever now? Laughing

You just want to be hated more than the guy curing his yellowing takumar with a sledgehammer Laughing


PostPosted: Sun Oct 18, 2009 8:49 pm    Post subject: Reply with quote

Lens flaws and image quality decline vari so much it will be impossible to perform a truly meaningful test.

It would be better to offer the lens fir free to someone who needs him.

Poor little orphan lens. You were going to kill him Sad

Wink


PostPosted: Sun Oct 18, 2009 8:52 pm    Post subject: Reply with quote

poilu wrote:
this could be interesting
I found degradation appear with a sample UV filter
Maybe I should try a scratched UV filter
or even better, a UV filter without front element


or even better, a UV filter without front element

Thanks poilu! I just about choked on my vegetable soup.... Laughing


PostPosted: Sun Oct 18, 2009 8:53 pm    Post subject: Reply with quote

Don't do it.


PostPosted: Sun Oct 18, 2009 8:57 pm    Post subject: Reply with quote

Keep it original. Attila needs the lens for his forthcoming lens museum Wink


PostPosted: Sun Oct 18, 2009 8:59 pm    Post subject: Reply with quote

you can even try out whether removing the grease from the screw channel has an effect on IQ!?

or even better:
paste a new caption over the old lens caption! try to name the pentacon "planar" and see how IQ is changing! perhaps you can also change the aperture number from "1.8" to "1.2" and watch if the lens is getting faster!?

btw: nice idea, spotmatic!


PostPosted: Sun Oct 18, 2009 9:58 pm    Post subject: Reply with quote

I submit a suitable candidate:

http://tinyurl.com/yjsn24b

-


PostPosted: Sun Oct 18, 2009 10:10 pm    Post subject: Reply with quote

I submit a suitable candidate:

Laughing Laughing Laughing


PostPosted: Mon Oct 19, 2009 12:07 am    Post subject: Reply with quote



PostPosted: Mon Oct 19, 2009 12:10 am    Post subject: Reply with quote

Mike Deep wrote:


impressive "shot"...


PostPosted: Mon Oct 19, 2009 12:11 am    Post subject: Reply with quote

Wow, that's one way to do it. So what was the victim?

Last edited by cooltouch on Mon Oct 19, 2009 12:12 am; edited 1 time in total


PostPosted: Mon Oct 19, 2009 12:11 am    Post subject: Reply with quote

Arse In All can sell it ! Rare prototype lens used to test dispersion of lens fragments. Only used once ! IQ will not suffer !


PostPosted: Mon Oct 19, 2009 12:20 am    Post subject: Reply with quote

Mike Deep wrote:


broken glass can be repaired using superglue.


PostPosted: Mon Oct 19, 2009 6:33 am    Post subject: Reply with quote

NO!

You bastards


PostPosted: Mon Oct 19, 2009 10:29 am    Post subject: Reply with quote

siriusdogstar wrote:
Mike Deep wrote:


broken glass can be repaired using superglue.


Glass has some small scratches, but will not affect image quality at all!

I found this lens on a log in my father's estate and know nothing about cameras. No returns, sold as is, MINT condition. Rare.


PostPosted: Mon Oct 19, 2009 11:29 am    Post subject: Reply with quote

Dust speckles, a few dents and cleaning marks don't mean the lens is unusable. Check this out:

http://www.lensrentals.com/news/2008.10.30/front-element-scratches


PostPosted: Mon Oct 19, 2009 11:37 am    Post subject: Reply with quote

Front element scratches are easy going - real element makes trouble!


PostPosted: Mon Oct 19, 2009 12:45 pm    Post subject: Reply with quote

Why don't you take a really worn lens for this experiment?
You can find lenses that have clean glass but suffer from really bad mechanics, stiff focus and the like. If you take a cheapo (such as a Pentaflex Auto-Color 1.8/50 or an on Helios-44 in such a poor condition you still can test on the detrioration of the optical performance.

mflex-on wrote:
Front element scratches are easy going - real element makes trouble!


Even then some lense are perfectly usable. I have got some lenses with clear cleaning marks at the rear element and they still perform excellently.


PostPosted: Mon Oct 19, 2009 8:33 pm    Post subject: Killing a lens for experimental purposes Reply with quote

This method is described as being for repair, but the protocol looks just right for achieving this experimenter's scientific goals:

http://www.hermes.net.au/bayling/repair.html


PostPosted: Mon Oct 19, 2009 8:40 pm    Post subject: Reply with quote

More seriously (?), we need to determine what level of rear element damage causes practical problems. Rear element paranoia may not be based too much in fact, even though it's plausible.


PostPosted: Mon Oct 19, 2009 8:54 pm    Post subject: Reply with quote

ramiller500 wrote:
More seriously (?), we need to determine what level of rear element damage causes practical problems. Rear element paranoia may not be based too much in fact, even though it's plausible.


I did test deep scratch on rare element was visible above F8.

Deep scratch on front element invisible at every aperture.