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honeypot.JPG
15-Nov-2013

honeypot.JPG


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Lensrentals16-Nov-2013 01:42
first some history about the lens (before the contest started)
the lens is an old sigma 70-300 DL whith a nikon mount. I bought it on the flea market. when i wanted to take it home i put it on the back of my bike secured by some rubber staps. i stepped on the bike and went over a curb. i heard a strange sound behind m, when i looked ,i saw the lens i just bought bouncing on the road. i quickly pulled over a grabbed the lens. optics looked fine, no broken glass fortunately. i didnt want to risk the lens hitting the floor again so i had the lens in my coat pocket all the time (i wondered why i didn't thought about that earlier) when i arrived home i tested the lens.
there was something strange about the lens. at 70mm i could get the lens in focus, but when zooming i could not achieve focus, even manually. i noticed that the rear element was kind of loose. when i hold the lens upside down the whole element shifted to the other side. The lens appeared broken, it could get worse so i tried to fix it. i dissembled the whole lens.almost every part had to be removed before i could get into the core.

when i finally could remove the element that shifted. i noticed what caused the problem.
the knobs the would slide in the slot element were broken.i measured the knobs, made a 3d model in solidworks and exported as a stl file.that file was send to a 3d printing service, and a week later a had the replacement parts in my mailbox.i put the lens together again and it worked.

so for this contest i knew how easy this lens is for disassembly. i can remove the front element(inc its casing) without using a screwdriver. i placed the honey pot inside and put the lens element back.

i set the focal length as low as posible (front element hit the honey pot) and placed a object on the optimal distace (eg where the subject would appear sharpest)

the subject is my mobile phone and in the background are some lamps. the lens was wide open, the hexagon shape is because of the shape of the honey pot ;)
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