Lens and Mirrors?

Question

A) A photographer moves closer to his subject and then refocuses. Does the camera move farther or nearer to the film?

B) Compare the mirror equation to the lens equation. What are some similarities and differences, especially the sign conventions afor the quantities involved.

Thanks

Answer 1

Answer to question A

The camera lense also moves nearer to the film.

As for your other question, right now I just dont have time to think about it, lol.

Cheers

Answer 2

Mirror equation and lens equation:

do^-1 + di^-1 = f^-1

Reciprocal of object distance plus reciprocal of image distance equals reciprical of focal distance.

Sign conventions are very complicated...

For MIRRORS, object distance is normally positive (only negative in multiple mirror/lens systems.)  It is the side where, well, the object is.

Image distance is positive if it is on the same side of the mirror as the object.

Focal distance is positive if it is on the same side of the mirror as the object.

For LENSES, object distance is normally positive (if the object is on the same side of the lens that the light is coming from, then it is positive (only a factor is complex multiple lens/mirror systems).

Image distance is positive if it is on the opposite side of the lens as the object.

Focal distance is positive for convex lenses and negative for concave lenses.  If the focal point is on the opposite side of the lens than the object, it is positive.

This is good information to have; you should print and keep this as reference until you are done with physics.

Answer 3

A camera lens is not a single lens, it is a lens system. In many systems, the lens closest to the film is fixed and does not move at all.

A camera lens reduces the effects of aberrations by replacing a simple lens with a group of lenses called lens elements, which are lenses of different shapes and distances of separation. The lens becomes more complex as greater correction of vision is achieved. The lens will also be more complex depending on the size of the aperture—the opening that allows light to pass