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Can I eliminate fungus with a money detector?


mr._scolari

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<p>Fungus can grow between cemented lens elements. Camera lenses are constructed using numerous individual lenses (elements). Some separated by an air space, others cemented together. The cement used until just after World War II was prepared from a natural resin created by the Canada Basam Fur Tree. Being an organic cement it is subject to supporting the growth of microorganism. In modern times Canada Balsam has been replaced by polyester and urethane and epoxy adhesives that likely will not support a culture of microorganisms.</p>

<p>Most times the lens ageing we see is actually a crazing of the cement used. The only remedy is to disable and re-cement. UV rays are energetic and kill microorganisms however sunlight is likely 1000 times more powerful than an artificial sources especially ones that generate UV using power derived from a low voltage battery.</p>

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<p>Money detectors usually emit long wave UV which won't do much to fend off fungi.</p>

<p>Germicidal lamps are shortwave.</p>

<p>Really, really, overdoing strong UV exposure will harm many elastomers/rubbers by inducing further cross-linking and making them essentially brittle.</p>

<p>I've replaced many insulators and cables from inside such exposure equipment zones.</p>

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<p>I think what Gert means is that if the iris of a lens is closed down while the lens is pointing towards the sun for a substantial length of time, the blades can be heated sufficiently to make the lubricants outgas, become more liquid-like and creep, etc. These processes may contaminate nearby glass surfaces, make the lubrication less effective, etc. </p>

<p>The same holds for non-SLR/dSLR lenses with built-in shutters, and you absolutely don't want to focus the image of the sun on a focal plane shutter for any length of time. </p>

<p>Tom M. </p>

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<p>Surely the focal plane shutter blinds are only exposed to the sun for a short time before and after the shot and the rest of the time the sun's rays are redirected away from the shutter through the viewfinder system, its mirror? This is not the case with some modern equipment?</p>

<p><strong>The danger of pointing the camera at the sun is to the human eye </strong>and possibly the electronics measuring the scene for exposure purposes. A freind was off-work with eye damage after he tracked a solar eclipse with his film camera for TV, a better system is to use a projected image behind the camera or perhaps a Wratten 87 incorporated into the viewfinder system for the occasion. That is based on my experience of shooting an eclipse with a Wratten 87 to reduce the strength of the light, cutting all visible light, the camera still used 1/4000 at f/8, 100 ISO. But the image in the viewfinder was extremely bright and worrying until the EVF adjusted itself to cope. My experience was some years after my freinds mishap. Though the image through the EVF was not the sun but rather an image generated by the camera ... still bright though.</p>

<p>You never focus the sun on the focal plane shutter blinds becuase they are in front of the film/sensor which is the actual focal plane?</p>

<p>The danger used to be of light bouncing around inside the camera and finding little gaps to fog the film sitting in the gate ... not a problem with a sensor which is only energised [etc] for the moment of exposure?</p>

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<p>JK, you are absolutely correct to emphasize the danger to the human eye and your other related comments.</p>

<p>The reason I ended my previous post with the comment, <em>"...you absolutely don't want to focus the image of the sun on a focal plane shutter for any length of time.."</em> was because of the brief diversion into using the sun to kill fungi, bleach lens yellowing, etc. I then started to imagine someone putting their camera on a tripod, and, leaving it pointed it at the sun because of some perceived benefit (eg, minimizing vibration with a long telephoto). I just wanted to be sure folks realized that this *really* isn't a good idea.</p>

<p>Tom M</p>

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