# Camera Optics Calculator - Depth of Field, Hyperfocal, Field of View, Exposure, Diffraction, Bokeh

> Photography optics calculator: depth of field, hyperfocal distance, field of view, exposure triangle, motion blur, NPF star rule, diffraction limit and bokeh.

- URL: https://qilingtools.com/en/physics/camera-optics
- Category: Physics Tools (https://qilingtools.com/en/physics)
- Tags: [Physics](https://qilingtools.com/en/tags/physics), [Education](https://qilingtools.com/en/tags/education)
- Last updated: 2026-10-29
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

A photography optics calculator built on exact thin-lens formulas. Set the sensor format, focal length and aperture, then see a depth-of-field diagram with the blur circle plotted against distance, compare framings with field-of-view overlays, solve for shutter, aperture or ISO and estimate motion blur and the longest star exposure without trails, check the Airy disk against the pixel size, and compare background blur across lens and sensor combinations.

## How to use

1. At the top pick a sensor format (full frame, APS-C, Micro Four Thirds, phone and more) and set the focal length, aperture and pixel count
2. In "Depth of field" drag the focus distance or click the diagram, and read the near and far limits, hyperfocal distance and background blur
3. In "Field of view" read the horizontal, vertical and diagonal angles and compare the frame with common equivalent focal lengths
4. In "Exposure" choose a scene brightness, solve for shutter, aperture or ISO, and estimate motion blur and star exposure times
5. Use "Diffraction limit" and "Background blur" for the diffraction-limited aperture, the best aperture for a near-to-far range and a blur comparison of several setups

## Features

- Exact depth-of-field and hyperfocal formulas with a log-distance diagram and blur curve; drag to focus
- Eight common sensor formats with crop factor, equivalent focal length, equivalent aperture and pixel pitch
- Field-of-view angles with framing overlays and the area covered at the subject distance
- Exposure triangle solver with equivalent exposures, sunny 16 and motion blur in pixels
- Astrophotography: 500 rule, simple and full NPF rule with declination, and star-trail length
- Airy disk drawn to scale on the pixel grid, diffraction-limited aperture and the optimal near–far aperture

## FAQ

### What circle of confusion should I use?

The circle of confusion is the largest blur that still looks sharp. The traditional value assumes an 8×10 inch print viewed at 25 cm and is about the sensor diagonal / 1500: roughly 0.029 mm for full frame and 0.019 mm for APS-C. If you judge images at 100% on screen, use something smaller, such as one or two pixel pitches, and the depth of field becomes much shallower. You can override the value in the tool.

### What is the hyperfocal distance good for?

Focusing at the hyperfocal distance H puts everything from H/2 to infinity inside the depth of field, the classic way to maximise depth in landscapes. H ≈ f²/(Nc), so shorter lenses and smaller apertures bring it closer. A 24 mm lens on full frame at f/8 has H of about 2.5 m, so focusing there keeps roughly 1.25 m to infinity sharp.

### Do smaller sensors really give more depth of field?

For the same framing and the same f-number, yes, because they use a shorter focal length and a smaller entrance pupil. Multiplying the f-number by the crop factor gives the equivalent aperture: an APS-C 56 mm f/1.4 behaves almost exactly like a full-frame 85 mm f/2.1 for depth of field and blur. The background blur tab computes everything at the same framing so you can check this directly.

### Does stopping down always make images sharper?

No. Smaller apertures increase depth of field, but diffraction spreads each point into an Airy disk 2.44λN wide. Once the disk spans about two pixels, pixel-level detail softens; that f-number is the diffraction-limited aperture. Smaller pixels reach it sooner: about f/9 on a 24 MP full-frame sensor and around f/2 on phone sensors. When you need both near and far sharp, the tool finds the aperture that minimises defocus plus diffraction.

### How long can I expose the Milky Way without star trails?

Earth's rotation moves the stars across the frame, so long exposures turn them into short lines. The old 500 rule (500 ÷ equivalent focal length) is too generous for today's high-resolution sensors. The NPF rule also accounts for aperture and pixel pitch, and its full form includes the star's declination, since stars near the celestial pole move more slowly. The tool shows each rule and the trail length in pixels at your shutter speed.

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