A 50mm lens doesn’t frame the same shot on every camera, this works out exactly what it’s equivalent to on the sensor size you actually care about.
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Crop Factor & Equivalent Focal Length Calculator
See what a lens actually looks like on a different sensor, between any two formats, not just "vs full frame."
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"Equivalent aperture" doesn't mean your exposure changes
This is the detail that trips people up: f/2.8 is f/2.8 on any camera, it lets in the same light per unit of sensor area and needs the same shutter speed and ISO for a correctly exposed shot regardless of sensor size. What DOES change with sensor size, for the same framing and f-number, is depth of field and how much total light hits the whole sensor, which affects noise. The "equivalent aperture" above answers a different, narrower question: what f-number on the comparison sensor would give roughly the same depth of field and total light-gathering as your lens does on your sensor. It's a useful way to compare systems, not a claim about how your camera meters a shot.
Crop factor calculator FAQ
What is a crop factor?
It's how much smaller a sensor is than a full-frame (35mm) sensor, expressed as a multiplier of the diagonal. An APS-C sensor with a 1.5x crop factor has a diagonal 1.5 times smaller than full frame, which is why a lens on it frames tighter than the same lens would on full frame.
How do I convert a focal length between two sensor sizes?
Multiply the focal length by the ratio of the two sensors' crop factors (or equivalently, the ratio of their diagonals). This calculator does that automatically for any two formats, not just "vs full frame," since the same math works between any pair of sensor sizes.
Does a smaller sensor really give a lens more "reach"?
It gives you a tighter crop of the same scene, which looks like more reach, but the lens itself hasn't changed, it's still gathering light and rendering perspective exactly as it would on any sensor. What changed is how much of that image circle the smaller sensor captures.
Does the "equivalent aperture" change my actual exposure settings?
No. An f-number is an f-number on any camera, it needs the same shutter speed and ISO for a correct exposure regardless of sensor size. The equivalent aperture shown here answers a different question, what f-number on the comparison sensor gives roughly the same depth of field and total light-gathering, useful for comparing systems, not for metering a shot.
What are the crop factors of common sensor sizes?
Roughly: full frame is 1.0x, Canon APS-C is 1.6x, Nikon/Sony/Fuji APS-C is 1.5x, Micro Four Thirds is 2.0x, and 1-inch sensors are about 2.7x. Medium format sensors are actually larger than full frame, so their crop factor is below 1.0x, this calculator computes the exact figure from real sensor dimensions rather than rounding to these commonly quoted numbers.
Free crop factor calculator by ANUPRESS
The lens never changes, only how much of it you’re using
A 50mm lens projects the exact same image circle regardless of what body it’s mounted on, what changes is how much of that circle a given sensor captures. A smaller sensor crops in tighter, which looks like more reach or a longer effective focal length, but the lens’s actual optics, its perspective and light-gathering, never moved. That distinction matters the moment you’re comparing gear across different sensor sizes rather than staying within one system.
“Equivalent aperture” answers a narrower question than it sounds like
f/2.8 needs the same shutter speed and ISO for a correct exposure on any camera, full frame or otherwise, that part never changes with sensor size. What the equivalent aperture figure actually answers is a comparison question: what f-number on a different sensor would produce roughly the same depth of field and total light-gathering as this lens does here. Useful for comparing systems side by side, not a claim about how any single camera meters a shot.
Angle of view is the number that actually stays constant
Convert a focal length correctly between two sensor sizes and the angle of view comes out nearly identical on both, which is the whole point, it’s the actual definition of “equivalent.” If the angle of view doesn’t match after a conversion, something in the sensor dimensions used was off, a useful sanity check when working out an equivalence by hand.