parfocal
/pɑrˈfoʊkəl/
adjective
- Describing a lens or set of lenses (such as on a microscope or camera) that stay in focus when the magnification is changed.
- The microscope has parfocal lenses, so you can switch from low to high power without refocusing.
- When using a parfocal telescope eyepiece, you can change magnification quickly and easily.
- Parfocal zoom lenses are popular among photographers because they maintain focus while zooming.