I was always wondering about this because I don’t understand why I can see random colorful pixels when shooting something in the dark…why is that?
In: 3
Okay, so there’s three main elements involved with creating a digital image (or even film). Overall, you have light passing through a lens which focuses the light onto a light-sensitive sensor/film which records the image.
Aperture: How big the hole is behind the lens that allows light past – bigger hole = more light. The tradeoff is that the larger the aperture, the narrower the field of focus is (basically, the range of distance that is in-focus to the camera)
Shutter Speed: How long the image sensor is exposed to the “image”. In traditional film and DSLR cameras, there is a physical shutter that opens to allow light in then closes again. This is done in software with smartphone cameras. Slower shutter speed = more light passing through = brighter image. The tradeoff is you’re more prone to blurry images with a slower shutter speed.
ISO: Sensitivity of the sensor/film – **This is what causes the “noise”**. Basically, the more you crank up the sensitivity, the more light is registered on a particular photosensitive cell, but the more prone to random errors you are.
So, let’s say you’re taking a picture in low light. In order for the image to look just right, you have to balance the tradeoffs between aperture, shutter speed, and ISO. You could open the aperture all the way, but then if you wanted a person and the wall behind them fully in focus that wouldn’t do. You could leave the shutter open for longer, but if you don’t have a perfectly steady hand or if anything you’re taking a picture of moves, the image might get some motion blur. You could crank the ISO up to max, however then you start getting more noise.
In reality, you’re balancing all three based on the situation at hand. Smartphones try to do this automatically but at the end of the day, the more light you have for a photo the better.
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