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focal ratio::noun | Spocien Dictionary
| Type | Words |
|---|---|
| Synonyms | f number, speed, stop number |
| Type of | ratio |
Examples of focal ratio
focal ratio
A high focal ratio also means the field of view will be narrow.
From the en.wikipedia.org
The drawback is the system will have a high focal ratio, with a correspondingly dim image, and some vignetting.
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The lens aperture is usually specified as an f-number, the ratio of focal length to effective aperture diameter.
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For comparison, an ellipse has a constant sum of focal distances, a hyperbola has a constant difference of focal distances and a circle has a constant ratio of focal distances.
From the en.wikipedia.org
The effective f-number is proportional to the ratio between the lens focal length and aperture diameter, the diameter itself being proportional to the square root of the aperture area.
From the en.wikipedia.org
For a given subject framing and camera position, the DOF is controlled by the lens aperture diameter, which is usually specified as the f-number, the ratio of lens focal length to aperture diameter.
From the en.wikipedia.org
