DESIGN · FREE TOOL

Photography simulator

Move a setting. See the focus and framing change.

Set up your shot

Focal length50 mmAperture · f-number2.8 Focus distance · meters5.02 mPerson distance along path · meters5 mTree distance along path · meters15 mSensorComposition guides Keep the head in focus as the person moves

Move a slider or use its arrow keys. A smaller f-number gives a wider aperture. Focus distance changes the focus plane; person distance moves the subject along the path. Trees stay behind the person. The camera aims at the center of the head.

Hyperfocal focus is available when its calculated distance fits within 100 m. Auto-focus turns off when you choose it.

Your camera view

Head-tracking view · fixed ground plane · illustrated blur. Long lenses naturally crop the body; feet never move off the path.

—Near focus

—Far focus

—Depth of field

—Hyperfocal distance

Where the sharp zone falls

Blue band: acceptable sharpness. Dashed gold line: focus plane. Optical-axis distances are to scale; figure heights and view cone are schematic. Far focus may extend beyond the displayed scale.

Understand the shot before you take it.

Aperture

Opening from f/8 to f/2.8 makes the acceptable-focus zone thinner at the same lens, distance and sensor. Exposure is held constant in this illustration.

Lens and distance

A longer focal length narrows the view. Moving the person changes perspective and framing; the camera tilts to keep the head centered. Changing focal length zooms the entire scene around that same aim point.

Sensor size

A smaller sensor crops the view at the same lens and position. The acceptable-sharpness assumption also changes. This is not a statement that crop factor changes a lens’s physical focal length.

The model, with its assumptions visible

Distances use a paraxial thin-lens model in millimeters, converted to meters for display. H = f²/(N × c) + f. Near = s × (H − f)/(H + s − 2f). Far = s × (H − f)/(H − s), or infinity when s ≥ H. f is focal length, N the f-number, s focus distance and c the accepted circle of confusion. Blur at scene distance z = f² × |z − s| / (N × z × (s − f)).

Conventional circle-of-confusion assumptions: 0.030 mm full frame, 0.020 mm APS-C and 0.015 mm Micro Four Thirds. These depend on viewing conditions, not just pixels. The scene uses a shared 3D perspective projection: the camera is 1 meter above a level ground plane and tracks a head center 1.45 meters above the path. The person is 1.65 meters tall. Trees, path and person all follow the same projection. Sensor aspect ratio is preserved. Focusing and subject position are separate. Defocus is a Gaussian approximation to the calculated blur-circle diameter, capped for rendering performance; it is not a calibrated optical point-spread function. It does not model diffraction, lens aberrations, focus breathing, real bokeh shapes, exposure, ISO noise, motion or macro pupil magnification. Keep those limits in mind for real lens decisions.

Reference: Stanford CS178: lenses, apertures and depth of field. Original Toolfred code and illustration; no third-party simulator code or artwork is copied. No photo upload, account, camera permission or paid API.