Pinhole Size Calculator
Enter the distance from the pinhole to the film or sensor and, if you like, a light meter reading at f/16. The calculator gives the best pinhole diameter, the f-number and the exposure time to use.
- Pinhole diameter
- f-number
- Exposure time
Focal length is the distance from the pinhole to the film or sensor.
The sharpest pinhole balances blur from the hole size against blur from diffraction. The best diameter is 1.9 × √(focal length × wavelength). For a 50 mm camera in green light that is about 0.31 mm, giving f/159. A meter reading of 1/125 s at f/16 becomes about 0.8 s.
Pinhole size chart
Green light, 550 nm. Search for a focal length.
| Focal length (mm) | Pinhole (mm) | f-number |
|---|---|---|
| 20 | 0.199 | 100 |
| 25 | 0.223 | 112 |
| 35 | 0.264 | 133 |
| 50 | 0.315 | 159 |
| 75 | 0.386 | 194 |
| 100 | 0.446 | 224 |
| 150 | 0.546 | 275 |
| 200 | 0.63 | 317 |
| 300 | 0.772 | 389 |
Best diameter.
Focal length and pinhole
Green light. Slide the focal length.
Light crosses at the pinhole and forms an image on the back.
How to make a pinhole
Size to exposure. Step through it.
Focal length
Measure.
Drill or pierce thin brass shim, then sand the burr off both sides for a clean edge.
Short, normal or long pinhole
Focal lengths. Compare them.
Under 30 mm.
About 50 mm.
Over 100 mm.
Wide pinholes cameras give a strong vignette at the corners.
Before you shoot
Pinhole checks. Tick each item.
Tick each item as you go.
Use a tripod. Pinhole exposures are long.
What you get
Pinhole sizing. Each tile explains one result.
mm.
Ratio.
Time.
Of view.
Inches.
A pinhole that is too small blurs from diffraction. Too large blurs from the size of the hole.
Frequently Asked Questions
No question matches that search.
What size pinhole is best?
About one point nine times the square root of the focal length times the light wavelength.
What is the f-number of a pinhole camera?
The focal length divided by the pinhole diameter, often around f/150 to f/250.
How do I work out pinhole exposure?
Take a meter reading at f/16 and multiply by the f-number over sixteen, squared.
Does the pinhole size change sharpness?
Yes. Too small and too large both blur the image.
How do I measure a pinhole?
Scan it at high resolution or look through a magnifier with a scale.
Why are my pinhole photos dark at the edges?
Light reaches the corners at a slant and travels further, which vignettes the image.
Do I need to allow for reciprocity?
For film exposures over about a second, usually yes.
Sharp through a pinhole
Make the hole the right size for your camera, and the soft magic of pinhole photography comes out crisp.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.