focal length in a sentence

Examples

1. Astronomers such as Johannes Hevelius were constructing telescopes with focal lengths as long as.
2. What is its focal length range for the zoom feature?
3. It also removes the need to have separate viewfinders for different lens focal lengths.
4. You need the focal length of the lens in use.
5. It had a diameter, focal length speculum metal objective mirror.
6. Optical zoom is actual magnification that shows true focal length.
7. This becomes more problematic with short focal length telescopes which require larger secondary mirrors.
8. Both the and Newtonian reflectors were F5 in focal length.
9. The focal length f is considered negative for concave lenses.
10. The distance from the mirror to the focal plane is called the focal length.