 Elijah J. Kihlstadius |
Weird spots in picture.
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Alan N. Marcus |
Hi Elijah, The spots that look like rings or concentric rings are “Newton Rings” These are formed when a thin film of oil sit on a surface like oil on a wet road (oil on water. Likely this is the cover glass of your camera’s light sensitive chip. Likely an oily fingerprint or the like, the other spots seem to be dust or like also on the cover glass. Maybe oil film over all somehow maybe high heat in an automobile etc.. You can clean with care. I use I advise ethyl alcohol (100 proof or better grain alcohol i.e. vodka ) I often use EverClear from the lacquer store cut 50% distilled water on a clean well washed T-shirt. Remember I am happy-go-lucky so in a pinch I use injection grade alcohol from the drug store (methyl alcohol) but I truly (no joke) prefer vodka. You might choose to have your camera professionally cleaned or choose expense kits that contain methyl alcohol. Best of luck, Alan Marcus
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Elijah J. Kihlstadius |
Both my lens elements appear to be in pristine condition. I think you are right it is my camera sensor. Am I going to have to pay an arm and a leg to get it cleaned? Where would be the best place to do it? I have a ritz camera right near where I live...
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Alan N. Marcus |
Hi again Elijah, This is not rocket science; you can do it yourself. Look on the web for advice and/or purchase a cleaning kit. Again I use an old well-washed clean T-shirt with a drop of vodka on it. Start in the middle and work outward in a circular motion. You can do it if you spend the night in a Holiday Inn Express. Alan Marcus
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- Dennis Flanagan Contact Dennis Flanagan Dennis Flanagan's Gallery |
The company visible dust (www.visibledust.com) has sensor cleaning kits. It is a fairly easy to do. My advice is be careful about using too much cleaning solution. If used to liberally, you will end up with streaks when it dries.
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Elijah J. Kihlstadius |
Thanks guys! I think I will first try cleaning my lens, then after that if ti still happens I will see about cleaning my sensor (er, the high-pass filter in front of it ;-)
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Alan N. Marcus |
Spots and dirt on the lens are reproduced out of focus. These spots are on the protective cover glass of the sensor. On your lens and on your sensor too much liquid can harm. On your sensor too much pressure will harm. However the sensor cover glass is easly cleaned. Just use light pressure. Alan Marcus
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Elijah J. Kihlstadius |
Well I was using a reversed lens and it was at F32 remember?
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Christopher A. Walrath |
Elijah, Alan is spot on on this one. If you choose to follow his advice you would be in good shape.. Alan is the king of gobbledygook round these here parts. Besides, you'll already have the vodka for the celebratin'. Keep on rolling
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Alan N. Marcus |
Hi agin Elijah, Foreign objects on the sensor cover glass obstruct light rays. These besprinkles are always present however they are most likely to be revealed under two conditions. A. When imaging a mundane view (large expanse of sameness). B. When tiny apertures like f/22 or f/32 are employed. Why? B. Light is bent inward by the lens. Converging rays take on the shape of a cone. When correctly focused the apex of this cone of light just kisses the surface of the sensor chip. The spot of light produced is a tiny, almost immeasurable circle, known as the circle of confusion. Now the chip is protected by a cover glass that hovers over its surface. Imaging light rays must transverse this protector. At the elevation of the cover glass, the light rays have not yet converged, i.e. their shape is a tiny but still measurable circle. Should this circle of light fall on a foreign object a shadow is formed on the surface of the imaging chip below. This shadow is the artifact we are talking about. The shadow will be deep and dark at its center (umbra). The edges of the shadow are diffused and muted (penumbra). At large apertures the larger size of the out-of-focus circle of confusion, at the elevation of the cover glass, will likely be larger than the artifact. Thus at large apertures a high percentage of image forming rays will pass by the artifact unaltered. This condition scatters light into the umbra. Now the distinction between umbra and penumbra becomes even more hazy. Thus the effect of artifacts when using large apertures is minimized, may even go unnoticed. At tiny apertures like f/22 or f/32 the converging circle of confusion, at the elevation of the cover glass, is tiny indeed. Often it will be completely eclipse by the foreign object. Thus tiny apertures amplify the effect of dirt on the cover glass. Remember: The countermeasure is -- keep the cover glass clean and neat. Alan Marcus, Anaheim, CA (marginal technical gobbledygook) But four young Oysters hurried up,
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