I Do binoculars change the distance which the eyeball focuses?

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When you look at an object, say, for example, 30 feet away, your eyeballs adapt to focus at that distance of 30 feet.

When you look at the same object through a pair of binoculars, at what distance do your eyeballs adapt to focus at?

Is it more or less than 30 feet?

This is not a question about human biology, but about geometric optics. In other words, what is the focal distance of an image seen through a pair of binoculars
 

Orodruin

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This depends on the lens configuration of the binoculars. Most binoculars will have the possibility to change this, placing the image at varying distances and allowing you to put what you want to have in focus in focus. This also allows people with myopia to use the same binoculars to see the same object, but with different lens distance.
 
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This depends on the lens configuration of the binoculars. Most binoculars will have the possibility to change this, placing the image at varying distances and allowing you to put what you want to have in focus in focus. This also allows people with myopia to use the same binoculars to see the same object, but with different lens distance.
Is the focal distance usually larger or smaller than the original focal distance?
 

Orodruin

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Is the focal distance usually larger or smaller than the original focal distance?
The typical thing for your eyes to relax is to place the virtual image at infinity (unless you suffer from myopia).
 

sophiecentaur

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When you look at the same object through a pair of binoculars, at what distance do your eyeballs adapt to focus at?
It's really up to the user. The 'focus' wheel can place the image anywhere from 'fairly close' (depending on the design), through a relaxed few metres and to 'infinity' (and beyond - to quote Buzz Lightyear).
If you want to experiment with your bios, you can set the binoculars to your preferred image distance, use just one tube and see if you can judge what other objects, viewed with the other eye, appear to be at the same distance. Some people find this exercise easy and others find it impossible. There is an alternative 'parallax method' which is complicated to describe but it's a common method used in School Optics experiments. Google it if you're interested.
 

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