Lens Cleaning

[Enbee]

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I have a voigtlander 15mm version 3 lens. I bought it new sometime back but there seem to be some visible marks in my photographs. I was wondering how or what should be done to clean the lens.

[Peter Kilmister]

In my experience, visible marks are usually caused by dust on the sensor of the camera. Check that your lens has no fungus or dust by opening the lens aperture and looking through it against a blank white background such as a fridge door. If it looks clear then use the sensor detection option on your camera, in the menu.

 

You will have to take a test shot against a plain white background using the lens aperture fully closed. If dust spots show up then get your rocket blower out or send the camera to a specialist to get the sensor cleaned. You can do it yourself if you know what you are doing. Good luck.

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[jaapv]

The lens will only show visible marks, if any, from considerable dirt on the rear element. The sensor is far more likely.

[Enbee]

Thank You. Will check. The other lenses seem to be ok.

[Exodies]

Why does the visibility of sensor dust depend on the aperture?

[jmahto]

Why does the visibility of sensor dust depend on the aperture?

Sensor dust is close to the sensing elements, but not on the sensing elements (separated by glass thickness). Distant light coming from a wide area (wide aperture) spreads the dust shadow (imagine shadows forming from different angle, making blurry shaded area underneath each dust spot). For narrow light source, the dust shadow becomes more well defined with sharper shadow edges.

 

Another analogy is blurry shadow inside room from window light (wide light source) whereas outside in the Sun, shadows have more well defined edges.

Edited July 15, 2018 by jmahto

[Exodies]

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Thanks. Sensor glass thickness is what I forgot to think about.