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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesA lens conversion factor—usually called crop factor or focal length multiplier—describes how a camera sensor’s size affects the field of view captured by a lens, relative to a 35 mm full-frame camera. To find the full-frame-equivalent field of view, multiply the lens’s actual focal length by the camera’s crop factor.
What does lens conversion factor mean?
In photography, “lens conversion factor” generally means the crop factor: a ratio comparing a camera sensor with a reference format, most commonly 35 mm full frame. The smaller sensor records a narrower portion of the lens’s projected image, so the scene appears more tightly framed than it would on the reference format. Nikon also calls this ratio the “focal length multiplier.” Nikon’s glossary explains the multiplier and field-of-view comparison.
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The factor is based on the ratio of the sensor diagonals. It describes a framing comparison, not a physical alteration to the lens.
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →How do you calculate 35 mm-equivalent focal length?
Use this formula:
35 mm-equivalent focal length = actual lens focal length × crop factor
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For example, Nikon gives a DX crop factor of approximately 1.52×. Using the rounded 1.5× factor in its illustration, a 50 mm lens gives a field of view similar to a 75 mm lens on full frame: 50 × 1.5 = 75. The result is an equivalent for framing, not the lens’s new optical focal length. Nikon’s DX and FX explainer provides the example.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Does crop factor change the lens’s actual focal length?
No. Focal length is an optical property of the lens, expressed in millimeters; it is not the lens’s physical front-to-back length. A 50 mm lens remains a 50 mm lens when mounted on a camera with a different sensor size. The sensor changes how much of the projected image is recorded, which changes the framing compared with full frame. Nikon’s focal-length guide explains the relationship between focal length and angle of view, while Canon distinguishes marked focal length from conversion factor.
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What to remember
- Lens conversion factor usually refers to crop factor, compared with a reference sensor format.
- Multiply actual focal length by the crop factor to estimate the full-frame-equivalent field of view.
- The equivalent describes framing; it does not change the lens’s actual focal length.
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