Why do different types of lenses have different effects on image size and focus?

In summary, there are two demos that demonstrate the behavior of lenses and their effect on image size and focus. For BiConvex Lenses, increasing the lens radius results in a smaller image and a closer focus, while for the eye, contracting the ciliary muscles to fatten the lens leads to a larger image and closer focus. This may seem conflicting, but it is due to the differences in the lenses being used. Increasing the refractive index of a lens does indeed cause the image to focus closer to the lens. It is important to note that in the first demo, increasing the lens radius refers to the radius that is always double the focal length, not the radius of the glass lens itself. This explains the difference in behavior between the
  • #1
Hereformore
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So for BiConvex Lenses, increasing the lens radius (by making the lens fatter) brings the image and focus closer to the lens, thus making it smaller given constant object position. As demonstrated in this demo
http://micro.magnet.fsu.edu/primer/java/lenses/lensvariations/index.htmlYet for the eye, when we want to focus on closer objects, the ciliary muscles contract to fatten the lens and that makes the image larger, not smaller? As demonstrated in this demo: http://micro.magnet.fsu.edu/primer/java/humanvision/accommodation/index.html

Why are they conflicting? Are they different lenses?

And while we're on the subject, increasing the refractive index of a lens definitely causes the image to focus closer to the lens right?
 
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  • #2
I don't know what you are seeing, but when I increase the lens radius in the first link, the focus moves further away from the lens. This would make it consistent with the second demo.
 
  • #3
TheDemx27 said:
I don't know what you are seeing, but when I increase the lens radius in the first link, the focus moves further away from the lens. This would make it consistent with the second demo.
Sorry i wasnt clear! When i said radiuss i meant the radiuss that is always double the focal length, not the radius of the glass lens itself.
 

1. What is the relationship between lens radius and image size?

The lens radius determines the curvature of the lens, which in turn affects the size of the image produced. A larger lens radius will result in a larger image, while a smaller lens radius will produce a smaller image.

2. How does changing the lens radius affect the quality of the image?

Changing the lens radius can greatly impact the quality of the image. A larger lens radius can result in a sharper and more detailed image, while a smaller lens radius may cause distortion and decrease image quality.

3. Can the lens radius be adjusted on a camera?

Yes, most cameras allow for adjusting the lens radius. This can be done manually by changing the lens or using zoom functionality on the camera.

4. How does the distance between the lens and the subject affect the lens radius?

The distance between the lens and the subject does not directly affect the lens radius. However, it can impact the size of the image produced and may require adjusting the lens radius to achieve the desired image size.

5. Is there an ideal lens radius for all types of photography?

There is no one-size-fits-all ideal lens radius for photography. The best lens radius will depend on the type of photography and the desired outcome. For example, a larger lens radius may be preferred for landscape photography to capture more detail, while a smaller lens radius may be preferred for portrait photography to avoid distortion.

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