eli5: Why do cameras and other devices use more lenses and not just one more versatile lens?
In: 19
The main reason is to fight chromatic aberrations.
You can prevent this problem by “balancing the lenses” to cancel the aberration one with another. But this works at a fix focal lenght.
A movable set of lenses will eventually have aberrations on each end. The more variable lenght, the more aberration you will get.
So, for a perfect photo you need a good lens with fix lenght. Aka fix 35, fix 50, fix 200. But you have to carry all the different sets and stop in a clean place to swap them. If you are in a studio, you can easily have 30kg bags of lenses to swap, to always have the one that fits the picture.
for practicality is doable to carry short ranged zooms, like 35-60, 70-150. That’s the most commonly carried.
A extreme zoom like a 25-200 is gonna totally suck at both ends. Will suck at 25, be decent between 45 and 100, and suck again toward 200. But it’s a thing I used to have, if I have to stay in a dirty place, I don’t want to open the camera to change lenses. I’ll take slightly worse pictures, in favor of being able to zoom onto unexpected things. Like if I hike, I want to take a picture of a landscape but if a deer appears, I want to have a zoom. That’s where the broad range sets are good. You can still do pictures without aberration at the very center of the zoom range.
As you see it’s a trade off, between practicality and quality.
Google Chromatic aberration to see what type of distortion is.
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