Exposure Triangle Calculator
Calculate correct exposure settings balancing aperture, shutter speed, and ISO. Enter values for instant results with step-by-step formulas.
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Exposure Value (EV) is calculated from the f-number (aperture), shutter speed in seconds, and ISO sensitivity. Equivalent exposures have the same EV value. Changing one parameter by one stop requires compensating with another parameter by one stop in the opposite direction.
Last reviewed: December 2025
Worked Examples
Example 1: Portrait: Switching from Sharp to Blurry Background
Example 2: Indoor Event: Compensating for Low Light
Background & Theory
The Exposure Triangle Calculator applies the following established principles and formulas. Hobbies and crafts encompass an extraordinarily diverse range of practical skills, each with its own embedded mathematics. In knitting and crochet, yarn weight classification (lace, fingering, sport, worsted, bulky) determines gauge, typically expressed as stitches per 10 cm or per 4 inches. Yardage calculation requires knowing the area to be covered, the stitch pattern's yarn consumption rate, and a swatch-verified gauge, making it essential to buy sufficient yarn before a dye lot is exhausted. Fabric requirement calculation for sewing projects involves scaling a pattern to the correct size, accounting for seam allowances, fabric grain direction, and pattern repeat in printed textiles. Wood measurement in the United States commonly uses board feet, a volume unit defined as 1 inch × 12 inches × 12 inches. A board 2 inches thick, 6 inches wide, and 8 feet long contains (2 × 6 × 96) / 144 = 8 board feet. This unit allows lumber to be priced by volume regardless of dimensional format. Photography's exposure triangle describes the interdependence of aperture (f-stop), shutter speed, and ISO sensitivity in determining correct exposure. Each stop of change in any one variable doubles or halves the light reaching the sensor; maintaining correct exposure requires compensating with equal and opposite stops in one or more of the other variables. Music tempo is measured in beats per minute (BPM), and the mathematical relationship between BPM and note duration is precise: at 120 BPM, a quarter note lasts exactly 500 milliseconds, an eighth note 250 milliseconds, and a dotted quarter note 750 milliseconds. This relationship is fundamental to sequencing software, metronome use, and synchronising audio with video. Colour mixing in paint or pigment follows subtractive colour theory, where mixing primaries in specific ratios produces predictable secondary and tertiary colours, though the exact outcome depends on the pigment density and medium. Origami design relies on the consistent proportionality of square paper, with base fold ratios governing the proportions of the finished model.
History
The history behind the Exposure Triangle Calculator traces back through the following developments. Craft production has been central to human culture for millennia, but the social organisation of skilled making underwent a decisive transformation in medieval Europe with the formation of craft guilds. These associations regulated training through apprenticeship, maintained quality standards, and controlled access to trade in specific goods such as textiles, metalwork, and woodworking. The guild system began to decline with industrialisation in the 18th and 19th centuries, as machine production displaced artisan labour. A cultural reaction to industrialisation emerged in Britain in the 1880s through the Arts and Crafts Movement, led by designer and theorist William Morris. Morris advocated for the intrinsic value of handmade objects and sought to restore dignity to craft labour, influencing architecture, textile design, book arts, and furniture making across Britain and the United States. The Victorian era also saw a broad expansion of middle-class hobby culture, with pursuits such as watercolour painting, embroidery, botanical illustration, and amateur natural history becoming markers of respectable leisure. The post-World War II period brought mass commercialisation of hobby supplies, as rising consumer incomes and the growth of the suburban lifestyle created demand for craft kits, model making, and DIY home improvement. Specialty retailers and hobby magazines proliferated through the 1950s and 1960s. The maker culture revival of the early 21st century represented a second wave of reaction to mass production, this time catalysed by digital fabrication technologies. Make magazine, launched in 2005, became the flagship publication for a community combining traditional craft skills with electronics, 3D printing, laser cutting, and open-source software. The democratisation of 3D printing through affordable desktop machines from around 2010 allowed hobbyists to design and produce custom parts, figurines, and tools at home. Online craft communities including Etsy, launched in 2005 as a marketplace for handmade goods, and Ravelry, founded in 2007 as a social network for knitters and crocheters, created global infrastructure for craft sharing, pattern distribution, and materials exchange.
Key Features
- Solve the photography exposure triangle by entering any two of aperture, shutter speed, and ISO to calculate the third value needed for a correct exposure, including equivalent exposure combinations.
- Transpose a piece of music from one key to any other key by a specified number of semitones, and calculate the beats-per-minute tempo needed to match a target feel or metronome marking.
- Calculate Elo chess rating changes after any game result using the standard expected score formula and the appropriate K-factor for the player's rating band and tournament type.
- Convert real-world measurements to model kit dimensions at any common scale such as 1:72, 1:48, 1:35, or 1:24, and convert between scales when adapting plans or parts from a different kit.
- Estimate the total yarn required for a knitting or crochet project by entering gauge, stitch pattern, and finished dimensions, with adjustments for yarn weight and fibre type.
- Calculate optimal plant spacing for any rectangular or raised garden bed, determine how many plants fit in the available area, and generate a row-and-column layout grid.
- Compute aquarium water volume in gallons or litres from tank dimensions, factor in substrate and decoration displacement, and calculate the maximum fish stocking level using standard bioload guidelines.
- Estimate calories burned on a hike based on distance, total elevation gain, body weight, and pack weight, using a metabolic equivalent model that accounts for gradient intensity.
Frequently Asked Questions
Formula
EV = log2(f-number^2 / shutter speed) - log2(ISO / 100)
Exposure Value (EV) is calculated from the f-number (aperture), shutter speed in seconds, and ISO sensitivity. Equivalent exposures have the same EV value. Changing one parameter by one stop requires compensating with another parameter by one stop in the opposite direction.
Worked Examples
Example 1: Portrait: Switching from Sharp to Blurry Background
Problem: Current settings: f/5.6, 1/125s, ISO 100. You want to shoot at f/2.8 for background blur. What shutter speed is needed?
Solution: Aperture change: f/5.6 to f/2.8 = +2 stops of light\nTo compensate, increase shutter speed by 2 stops\n1/125s + 2 stops = 1/500s\nCalculation: new SS = (2.8^2 x (1/125) x 100) / (5.6^2 x 100)\n= (7.84 x 0.008) / 31.36 = 0.002 = 1/500s
Result: New settings: f/2.8, 1/500s, ISO 100 (equivalent exposure)
Example 2: Indoor Event: Compensating for Low Light
Problem: Current settings: f/4, 1/125s, ISO 100. Image is 3 stops underexposed. What ISO is needed to keep the same aperture and shutter speed?
Solution: Need 3 stops more light via ISO\nISO 100 + 1 stop = ISO 200\nISO 200 + 1 stop = ISO 400\nISO 400 + 1 stop = ISO 800\nEach doubling of ISO adds one stop of sensitivity
Result: New settings: f/4, 1/125s, ISO 800 (3 stops brighter)
Frequently Asked Questions
What is the exposure triangle in photography?
The exposure triangle is a fundamental photography concept describing the relationship between three camera settings that control how much light reaches the sensor: aperture, shutter speed, and ISO. These three elements work together to determine the overall exposure (brightness) of an image. Changing one setting requires compensating with one or both of the others to maintain the same exposure level. For example, opening the aperture by one stop lets in twice as much light, which can be compensated by doubling the shutter speed or halving the ISO. Mastering this triangle is essential for creative control over depth of field, motion blur, and image noise.
How does aperture affect exposure and depth of field?
Aperture is the size of the lens opening, measured in f-stops (f/1.4, f/2.8, f/5.6, etc.). A lower f-number means a wider opening that lets in more light and produces a shallower depth of field (blurry background). A higher f-number means a narrower opening with less light but greater depth of field (more of the scene in focus). Each full f-stop change doubles or halves the light. The common full-stop aperture sequence is f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16. Portrait photographers typically use wide apertures (f/1.4 to f/2.8) for background blur, while landscape photographers use narrow apertures (f/8 to f/16) for front-to-back sharpness.
What is an EV (Exposure Value) stop and how are stops counted?
An EV stop is a standardized unit representing a doubling or halving of the amount of light reaching the camera sensor. One stop brighter means twice the light; one stop darker means half the light. Each of the three triangle elements uses stops: aperture changes by one stop when the f-number is multiplied or divided by the square root of 2 (approximately 1.414). Shutter speed changes by one stop when doubled or halved. ISO changes by one stop when doubled or halved. Most modern cameras allow adjustments in 1/3 stop increments for finer control. Understanding stops makes it easy to compensate between settings while maintaining equivalent exposure.
What are the best exposure settings for common photography scenarios?
For portraits, use f/1.4 to f/2.8 for background blur, 1/125s or faster to avoid motion blur, and ISO 100-400. For landscapes, use f/8 to f/11 for maximum sharpness, any shutter speed with a tripod, and ISO 100. For sports and action, use the widest aperture available, 1/500s or faster, and increase ISO as needed. For night photography, use f/2.8 or wider, 15-30 seconds on a tripod, and ISO 1600-6400. For indoor events, use f/2.8 or wider, 1/60s minimum, and ISO 800-3200. These are starting points that you should adjust based on your specific conditions, creative intent, and equipment capabilities.
How do I maintain equivalent exposure when changing one setting?
Equivalent exposure means adjusting other settings to compensate when you change one, keeping the overall image brightness the same. The rule is simple: for every stop of light you add with one setting, remove one stop with another. If you open the aperture from f/8 to f/5.6 (one stop more light), compensate by changing shutter speed from 1/125s to 1/250s (one stop less light) or dropping ISO from 400 to 200. Exposure Triangle Calculator automates this process by computing the required compensation. The creative difference is that while exposure stays the same, depth of field, motion blur, and noise characteristics all change based on which settings you adjust.
What is the 500 rule for astrophotography exposure?
The 500 Rule is a guideline for astrophotography that helps determine the maximum shutter speed before stars start to trail due to Earth rotation. Divide 500 by your effective focal length to get the maximum exposure time in seconds. For example, with a 24mm lens: 500 divided by 24 equals approximately 20 seconds. With a 50mm lens: 500 divided by 50 equals 10 seconds. For crop sensor cameras, multiply the focal length by the crop factor first (typically 1.5x or 1.6x). Some photographers prefer the more conservative NPF rule or the 300 rule for sharper stars. Beyond this time limit, stars will appear as short streaks rather than sharp points of light.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy