Can a dirty or scratched lens cause grainy-looking photos?
Asked 5/24/2016
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My point-and-shoot camera looks fine when photos are viewed fit-to-screen, but at 100% zoom the images look grainy, even in full daylight with auto ISO. Could dirt, smudges, or scratches on the lens cause this kind of graininess without causing obvious blur or visible marks in the whole image? Or is this more likely to be image noise from the camera itself?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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Yes, it's possible — but it's more likely that that's just how it is. You can't expect miracles from a point and shoot camera, and fine detail with no noise when "pixel peeping" would be a miracle. You say that the results are satisfactory for viewing as a whole on a computer screen. They'll also be fine when printed at reasonable sizes.
In any case, it's unlikely that the result of this would be something you'd describe as grainy. Instead, there might be a slight loss of sharpness and contrast, and (especially if it's grease and smudges rather than just dirt) glare/flare/ghosting. If you're seeing noise, that's probably just the natural result of a lot of pixels in a tiny sensor.
There may be some changes you can make to get somewhat better results, but I bet the pixel-level detail will still disappoint. See How can I make a very sharp photograph with a point & shoot camera? for more — but, mostly, don't set your expectations too high.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
10y ago
0
Generated from our catalog & community — verify before relying on it.
A dirty or scratched lens is very unlikely to cause what you’d describe as graininess. Dirt, dust, smudges, and minor lens contamination are so out of focus that they usually cause reduced contrast, softness, flare, ghosting, or a slight loss of brightness—not fine grain-like texture.
What you’re probably seeing is digital noise, especially when viewing a small-sensor point-and-shoot image at 100%. That’s normal: compact cameras pack many pixels onto a tiny sensor, and auto ISO may raise sensitivity even in daylight. At pixel level, noise can become obvious even if the image looks perfectly fine at normal screen size or in typical prints.
If you want to reduce it, try using the lowest ISO available, give the camera as much light as possible, and avoid judging compact-camera files too harshly at 100% zoom. If the photos look good at normal viewing sizes, the camera may be performing as expected.
Cleaning the lens exterior is fine if it’s visibly smudged, but don’t expect that to remove graininess.
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