Field of View Visualizer
Choose your sensor, dial in a focal length and a subject distance, and see the angle of view plus exactly how much of the scene fits in the frame at that distance — drawn from above, and again as five focal lengths cropping one scene. Instant, in your browser, no sign-up.
On full frame, a 50 mm lens at 10 m covers about 7.20 m × 4.80 m of the scene.
| Horizontal angle of view | 39.6° |
| Vertical angle of view | 27.0° |
| Diagonal angle of view | 46.8° |
| Frame width at your subject | 7.20 m |
| Frame height at your subject | 4.80 m |
Top-down view of the horizontal field of view; the drawing keeps the true angle, distances are schematic.
The scene is the 24 mm view on the selected sensor from a fixed spot; every tighter frame is a crop of the same scene — sensor choice scales all frames together.
How to read this
Two formulas do all the work. Angle of view = 2 × arctan(sensor dimension ÷ (2 × focal length)). Use the sensor width for the horizontal angle, the height for the vertical, and the diagonal for the figure lens makers like to quote. Frame width at the subject = distance × sensor width ÷ focal length — and the same shape with the sensor height gives the frame height. Nothing here is an estimate or a rule of thumb: it is plain geometry, so the numbers hold for any lens that honestly carries its marked focal length.
The crop factor is the same geometry seen from the other side. Put a 50 mm lens on full frame and it frames like a 50 mm lens. Put the very same lens on APS-C and the smaller sensor records only the middle of its image — the framing of a 75 mm lens on full frame. On Micro Four Thirds it frames like a 100 mm. That is the equivalent field of view: focal length × crop factor, with crop factors of 1, 1.5 and 2 for the three sensors above. The lens has not changed at all; the sensor is simply cropping its picture tighter.
One warning this visualiser cannot show you, because it is not about focal length at all: perspective. Perspective — how large things look relative to each other, how stretched or compressed a scene feels — is set by where you stand, and only by where you stand. Focal length merely crops the view from that spot. Step closer with a wide lens and faces stretch; step back with a long lens and backgrounds loom. In both cases it was the step, not the lens, that did it. Choose your position for the perspective you want, then choose the focal length that crops that view to the framing you want.
Focal length is a cropping decision
Lens marketing talks about focal length as reach and power, as if the number on the barrel were a measure of zoom. The geometry is plainer and more useful than that. A focal length, paired with a sensor, decides one thing: how wide a slice of the world lands on the sensor. A 24 mm lens on full frame takes in about 74 degrees horizontally — a generous slice that swallows rooms, streets and landscapes whole. A 200 mm lens takes in about 10 degrees, a narrow wedge that lifts one face, one bird or one doorway out of the scene and discards everything around it. Nothing in between those two extremes is a different kind of photography; it is the same slice, cut wider or narrower. That is what the second diagram above is showing you: the camera never moves, the scene never changes, and each tighter frame is simply a smaller crop of the widest one. Once you see focal length as cropping, a lot of lens advice falls into place — you are not buying magnification, you are choosing how much of the world each photograph is allowed to contain.
Sensor size changes what a lens “is”
The other half of the pairing is the sensor, and it is why the same lens can be a wide, a standard or a telephoto depending on the body it is mounted on. A 50 mm lens projects the same image circle whatever it sits in front of; a full frame sensor records most of that circle, an APS-C sensor records the middle of it, and a Micro Four Thirds sensor records a smaller middle still. Smaller record, narrower slice, tighter framing. So the 50 mm that behaves as a mild, honest standard lens on full frame frames like a 75 mm portrait lens on APS-C and like a 100 mm telephoto on Micro Four Thirds. Photographers call the conversion the crop factor, and it cuts both ways: crop shooters get free reach for sport and wildlife, and pay for it at the wide end, where a 16 mm lens is needed to do the job a 24 mm does on full frame. The maths is closely related to the sharpness maths — the same sensor sizes drive our depth of field calculator, which shows how sensor size also changes what stays sharp at a given aperture, and if you are planning a night shoot instead, the sharp stars calculator uses the same focal lengths to work out how long you can expose before the sky starts to move.
Planning with the numbers, not by feel
The coverage figures are where this stops being theory. Shooting an interior and wondering whether 24 mm is wide enough? Stand where the back wall forces you to stand, measure that distance, and read the frame width: at 4 metres a full frame 24 mm covers about 6 metres across, so a room narrower than that fits and a wider one does not — better to know before the shoot than during it. Arranging a group shot? At 5 metres, a 35 mm lens on full frame covers about 5.1 metres of width, enough for a row of eight to ten people standing comfortably; the same lens on APS-C covers only about 3.4 metres at that distance, which is a row of five or an argument. Working out wildlife distances runs the same calculation backwards: if you want a subject roughly a metre tall to fill the frame height with a 200 mm lens on full frame, the frame height reaches one metre at about 8 metres away — that is your working distance, and any hide, path or fence line can be judged against it. Planning gets the subject in the frame; keeping it sharp once it is there is technique, and our guide to taking sharp photos every time covers that side of the job.
Frequently asked questions
Is 50 mm what the eye sees?
Roughly, but not exactly — it is a useful approximation, not a match. A 50 mm lens on full frame has a diagonal angle of view of about 46 degrees, which is close to the central zone of human vision where we actually pay attention and see detail. But your full visual field is far wider than that — well over 100 degrees including peripheral vision, most of it vague and devoted to noticing movement rather than detail. So a 50 mm photograph feels natural because its proportions and perspective relationships resemble attentive looking, not because it reproduces the whole of seeing. Lenses from about 40 mm to 55 mm on full frame all sit in that natural-feeling zone, which is why the class is called “normal”.
Do I use the lens's marked focal length on APS-C?
Yes — always enter and think in the marked number first. The focal length printed on the lens is a physical property of the lens and it does not change when you mount it on a smaller sensor; a lens marked 35 mm is a 35 mm lens on any body. What changes is how much of its image the sensor records. This calculator handles that honestly: pick the APS-C sensor and enter 35 mm, and it shows the field of view the sensor actually gets. The “equivalent” figure — about 52 mm in that case — is only a translation for comparing framing across formats: it tells a full frame shooter what lens they would need for the same framing. Equivalents are for comparison, not a correction you apply to your lens.
What does a phone's “26 mm equivalent” claim mean?
Exactly the comparison above, run in the opposite direction. A phone sensor is tiny, so its actual lens is only a few millimetres long — but a few millimetres in front of a tiny sensor sees the same slice of the world as 26 mm in front of a full frame sensor. The equivalent number is the honest, comparable figure, and it is the one worth using: when a phone says 26 mm, you can open this visualiser, select full frame, enter 26 mm, and the angles and coverage it shows are the angles and coverage the phone delivers. Where equivalents stop applying is everything that depends on the physical sensor and lens rather than the framing — depth of field above all. The phone frames like a 26 mm full frame lens but keeps far more in focus, because its real focal length and sensor are so small.
Does a zoom behave differently from a prime at the same focal length?
Not for field of view — the maths is identical at every marked focal length. A zoom set to 35 mm and a 35 mm prime frame the same slice of the world on the same sensor, to within the small honesty tolerances of how manufacturers round and measure their numbers. One real-world caveat is worth knowing: many lenses, zooms especially, effectively shorten at close focus distances — a lens marked 200 mm may frame noticeably wider than 200 mm when focused on something a metre away. Photographers call it focus breathing. It does not change anything at landscape or portrait distances, but if your close-up framing looks a little wider than this calculator promises, that is the reason.