sunny16

sunny16 provides low-level calculations for the photographic units ExposureValue and LightValue. It is written in Typescript, well-tested and based on the underlying math detailed here.

Install

Run yarn add sunny16 or npm install sunny16

Constants & Terminology

The module comes with a set of data located in /constants/. Each data type can be accessed via a getter that supports clipping the data to different camera configurations.

shutterSpeeds

ShutterSpeeds are stored as objects that map a stopNumber to a nominal value. The exact value is derived from the stopNumber during calculations.

  { stop: -14, nominal:'1/16000' }

To retrieve and customize shutterSpeeds, the getter getShutterSpeeds(min?, max?) can be used. min/max are optional and can be set by passing a nominal value.

import { getShutterSpeeds } from 'sunny16';

const allShutterSpeeds = getShutterSpeeds();
const leicaShutterSpeeds = getShutterSpeeds('1/1000', '1');

fNumbers

fNumbers (commonly referred to as Apertures) are stored as objects that map a stopNumber to a nominal value. The exact value is derived from the stopNumber during calculations.

{ stop: -1, nominal: 0.7 },

To retrieve and customize shutterSpeeds, the getter getFNumbers(min?, max?) can be used. min/max are optional and can be set by passing a nominal value.

import { getFNumbers } from 'sunny16';

const allFNumbers = getFNumbers();
const summicronFNumbers = getShutterSpeeds(2, 16);

filmSpeeds

filmSpeeds are stored as numbers. To retrieve filmSpeeds, the getter getFilmSpeeds(min?, max?) can be used. min/max are optional and can be set by passing a number.

import { getFilmSpeeds } from 'sunny16';

const allFNumbers = getFilmSpeeds();
const summicronFNumbers = getFilmSpeeds(100, 400);

exposureValues / lightValues

ExposureValues describe the sensitivity to light. When related to a given filmSpeed, it can be used to determine correct camera settings for given lighting situations (the sunny16-rule works this way).

To retrieve exposureValues, the getter getExposureValues(min?, max?) can be used. min/max are optional and can be set by passing a number.

import { getExposureValues } from 'sunny16';

const allFNumbers = getExposureValues();
const summicronFNumbers = getExposureValues(-6, 21);

CameraSetting

A single camera setting (returned by cameraSettings()) has the shape:

  {
    fNumber: 5.6
    shutterSpeed: '1/200'
  }

config

A config object can be passed to cameraSettings() to pass camera-configuration. It has the shape:

  {
    fNumbers: getFNumbers(),
    shutterSpeeds: getShutterSpeeds(),
  }

Calculations

Get cameraSettings for a lightValue/filmSpeed combination

cameraSettings(lightValue, filmSpeed, config?)

• lightValue number: target lightValue
• filmSpeed number: target filmSpeed
• config object: configuration object, defaults to shutterSpeeds '1/1000'–'1' and apertures 2–16
• returns:

    {
      lightValue: number,
      filmSpeed: number,
      cameraSettings: cameraSetting[],
    }
  

import {
  cameraSettings,
  getFNumbers,
  getShutterSpeeds,
} from 'sunny16';

const config = {
  fNumbers: getFNumbers(2, 16),
  shutterSpeeds: getShutterSpeeds('1/1000', '1'),
};

const sunny16Settings = cameraSettings(15, 200, config);

Returned settings that are outside of config range will be filtered.

Get a lightValue for a given cameraSetting and filmSpeed

lightValue(nominalFNumber, nominalShutterSpeed, filmSpeed)

• nominalFNumber number: fNumber (in nominal representation)
• nominalShutterSpeed string: shutterSpeed (in nominal representation)
• filmSpeed number: filmSpeed
• returns: number

import { lightValue } from 'sunny16';

const lightValue = cameraSettings(2, '1/1000', 200);

Get an exposureValue for a given cameraSetting

exposureValue(nominalFNumber, nominalShutterSpeed)

• nominalFNumber number: fNumber (in nominal representation)
• nominalShutterSpeed string: shutterSpeed (in nominal representation)
• returns: number

import { lightValue } from 'sunny16';

const lightValue = cameraSettings(2, '1/2000');

Errors

The module will warn when passed invalid data. It throws a Sunny16Exception in that case that needs to be catch'ed.'