eli5: Why do cameras and other devices use more lenses and not just one more versatile lens?
In: 19
There are versatile lenses – but they become prohibitively expensive. It’s cheaper and more efficient to have specific lenses for specific purposes.
Some types of photography require certain lenses – and some types of photography cannot be obtained with certain types of lenses.
A close up macro lens is built very differently than a traditional wide angle because they require light to enter the lens and hit the sensor in different ways and the glass and mechanics need to be placed in the lens in certain ways.
Then you have aperture – which is the setting of how much light you let into the camera. Cheaper lenses have simpler mechanics, so as you zoom in, the aperture might need to close up (so the image gets darker as you zoom in).
More expensive lenses can have a constant aperture as you zoom in – but that requires more complicated mechanics – so the aperture is kept open using different mechanical offsets as the lens zooms in.
I’m on a video shoot right now where we have cinema-quality zooms (Angenieux brand) – each one is about $13,000 retail value. They’re about a foot and a half long each. It’s not very practical to carry around.
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