Eli5: How can there be ‘noise’ in an image?
In: Technology
To expand on some other answers here, there’s 3 main ways of adjusting the amount of light that is captured in an image, both in traditional film as well as digital photography.
The one you’re looking for is ISO:
ISO – Basically light sensitivity of the film or image sensor. A higher ISO means more sensitivity to light and a lighter image, however a higher risk of the sensor producing noise which can appear as miscolored speckles on the image. If you’ve ever noticed similar “noise” when you’re in a very poorly lit environment, that’s more or less the biological equivalent.
Aperture – how wide the opening between the lens and the camera opens. The wider the aperture, the more light gets in but also the shallower the depth of field – essentially, objects more quickly become out of focus from your point of focus as compared to a smaller aperture
Shutter speed – How long the shutter stays open to expose the film/sensor to light. The longer it’s open, the more light hits the film/sensor but the more risk of motion blur from an unsteady hand/motion/etc
Phone cameras and any point and shoot or DSLR in automatic mode will try to adjust all of these parameters as best as it can for the situation to try to capture a properly lit image with the best settings possible, however the less actual light available, the less likely it is to capture a flawless image. Setting things manually requires knowledge and practice but can help you make the best of a less than perfect lighting situation and capture what you want and minimize what you don’t want.
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