focal plane


: a plane that is perpendicular to the axis of a lens or mirror and passes through the focus

Examples of focal plane in a Sentence

Recent Examples on the Web Cons of Iron Sights for Hunters Unlike optical sights, which put the reticle and the target in the same focal plane and require your eye to focus on only that plane, iron sights involve three focal planes: rear sight, front sight, and target. David E. Petzal, Field & Stream, 30 Jan. 2023 The focal plane took six months to assemble. Ashley Strickland, CNN, 8 Sep. 2020 That said, the a7R V sports a pro-grade mechanical focal plane shutter, with support for electronic first curtain, but those are long-running features in the series. PCMAG, 31 Oct. 2022 Focusing is fast and accurate, the focal plane seems bigger, there’s no discernible shutter lag, and most of all: the pictures look better. Dieter Bohn, The Verge, 21 Jan. 2021 Every night between December 2009 and March 2019 that the moon was not overly bright, the telescope tracked a patch of sky, and the fibers fed the light that fell onto the focal plane into two spectrographs. Kyle Dawson, Scientific American, 1 May 2021 One end of each cable was supported by an aluminum plate positioned at the focal plane of the telescope. Kyle Dawson, Scientific American, 1 May 2021 In confocal microscopy the focal plane is imaged with a single, intense point of light, centered between two cones of light that flood the rest of the sample. Jen Christiansen, Scientific American, 21 May 2013 The first-focal plane design lets the shooter take maximum advantage of the reference marks in the reticle. Will Brantley, Field & Stream, 21 Dec. 2020

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'focal plane.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1840, in the meaning defined above

Time Traveler
The first known use of focal plane was in 1840

Dictionary Entries Near focal plane

Cite this Entry

“Focal plane.” Dictionary, Merriam-Webster, Accessed 25 May. 2024.

Medical Definition

focal plane

: a plane that is perpendicular to the axis of a lens or mirror and passes through the focus
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