Pinhole Camera Design & Exposure Calculator
Enter the camera depth, actual pinhole, frame size, and a meter reading to see the theoretical diameter range, real f-number, field of view, corner falloff, and shutter time.
Calculated pinhole exposure0.76
- Readable shutter time
- 0.763 seconds
- Recommended pinhole diameter
- 0.3
- Recommended diameter range
- 0.265 mm to 0.332 mm
- Actual diameter difference
- 7.2%
- Actual f-number
- 156.25
- Horizontal angle of view
- 39.6
- Vertical angle of view
- 26.99
- Diagonal angle of view
- 46.79
- Corner illumination
- 70.95%
- Corner light loss
- 0.5
- Exposure increase
- 95.37
- Exposure increase in stops
- 6.58
Diameter recommendations use the Carlsson 1.6 to 2.0 coefficient range and the selected design wavelength.
Exposure assumes a linear recording medium and does not include film or paper reciprocity failure.
How to use this calculator
- Measure the distance from the pinhole plate to the film or sensor plane.
- Enter the actual pinhole diameter you plan to drill, buy, or test.
- Choose the diameter criterion and design wavelength for the sharpness estimate.
- Enter the active frame dimensions so the angle of view and corner falloff match your format.
- Enter a meter reading at the same ISO to convert it to a pinhole exposure.
How the pinhole numbers are calculated
A pinhole camera trades lens focus for a small aperture. The hole must be small enough to limit geometric blur, but not so small that diffraction spreads the image too much. This calculator uses the Carlsson-style diameter range, then applies ordinary perspective and exposure relationships to the camera you enter.
The selected recommended diameter is:
d = c * sqrt(lambda * b)
- d is the recommended pinhole diameter in millimeters.
- c is the selected coefficient: 1.6, 1.8, or 2.0.
- lambda is the design wavelength converted from nanometers to millimeters.
- b is the pinhole-to-film distance in millimeters.
The range shown beside it uses the same formula with 1.6 and 2.0 as the lower and upper coefficients. Your actual pinhole is allowed to differ because real cameras often use available laser-drilled sizes or holes made by hand. The actual f-number is simply N = b / dActual.
For field of view, the calculator treats the pinhole as the center of projection. Horizontal, vertical, and diagonal angles use 2 * atan(frameDimension / (2 * b)). Corner illumination uses the ideal cosine-fourth law at the diagonal half-field angle: R = cos(theta)^4. The light loss in stops is -log2(R).
How the exposure is converted
Once the real f-number is known, a light-meter reading at another aperture can be converted by the square of the f-number ratio:
multiplier = (N / Nmetered)^2
pinhole time = metered time * multiplier
Distance and actual hole size move the exposure most. A slightly smaller pinhole raises the f-number and lengthens the exposure quickly because exposure changes with the square of the aperture ratio. Frame size does not change the center exposure, but a wider frame raises diagonal angle of view and darkens the corners.
What this calculator leaves out
The model assumes a round, clean, centered pinhole in a negligibly thin plate over a flat image plane. It does not account for ragged holes, plate thickness, off-axis clipping, curved film, shutter timing error, processing choices, scanner response, or scene contrast. The exposure result also assumes linear film, paper, or sensor response. Many films and photographic papers need reciprocity correction once exposures get long, so treat the result as the starting exposure before medium-specific testing.
Worked example
Suppose the pinhole-to-film distance is 50 mm, the actual hole is 0.32 mm, the balanced 1.8 criterion is used at 550 nm, and the frame is 36 mm by 24 mm. The square-root term is sqrt(0.00055 * 50) = 0.165831, so the recommended diameter is 1.8 * 0.165831 = 0.298496 mm. The 1.6 to 2.0 range is 0.265 mm to 0.332 mm, so the 0.32 mm hole is within range and is 7.20% larger than the selected recommendation.
The actual f-number is 50 / 0.32 = f/156.25. A 36 mm by 24 mm frame gives 39.60 degrees horizontally, 26.99 degrees vertically, and 46.79 degrees diagonally. The ideal corner illumination is 70.95% of the center, a loss of 0.50 stops. If the meter reads f/16 at 0.008 seconds, the exposure multiplier is (156.25 / 16)^2 = 95.37, so the pinhole exposure is 0.763 seconds.
Common questions
What is the best pinhole diameter for my camera?
A practical starting point is the 1.6 to 2.0 coefficient range shown by the calculator. The smaller end favors less geometric blur and more diffraction, while the larger end favors less diffraction and more geometric blur. A clean, round hole near the range often matters more than a tiny difference in the computed diameter.
Why do different pinhole formulas give different diameters?
They choose different compromises between diffraction and geometric blur, and some assume a different wavelength of light. The Carlsson range makes that compromise visible instead of treating one coefficient as universal. Use the range as a design target, then test with your film, paper, or sensor.
How do I measure pinhole-to-film distance?
Measure from the plane of the pinhole plate to the film, paper, or sensor plane along the camera centerline. In a box camera this is usually the inside depth from the pinhole plate to the image surface. If the film curves, use the center distance for this calculator and expect the edges to vary slightly.
How do I calculate the f-stop of a pinhole camera?
Divide the pinhole-to-film distance by the actual pinhole diameter, using the same units for both. A 50 mm camera with a 0.32 mm pinhole is f/156.25. That real f-number is the value used to convert the light-meter reading.
Why are the corners of a wide pinhole image darker?
The corners see the pinhole at an angle, so less light reaches each unit of image area than at the center. The ideal cosine-fourth law estimates that falloff from the diagonal half-field angle. Thick pinhole plates can add extra clipping beyond the ideal calculation.
Do I need reciprocity-failure compensation for film or paper?
Often, yes, once the calculated exposure is longer than about one second. The amount depends on the exact film or paper, developer, temperature, and target contrast. Use the calculator result as the metered baseline, then apply the correction recommended for your medium or found by testing.