“Photography is more than a record of light – it is an illustration of vision, where the lens becomes the brush and light the ink that sketches emotion onto time.” – MJ Martin
Deeply understanding light in photography is quickly becoming a lost art. Most cameras today are so automated and overloaded with AI features that modern shooters rarely consider light. They no longer need to worry about it.
Yet, light is the essence of photography so commanding a solid comprehension of the physics of light is still as mission critical as it was in the film days….!
UNDERSTANDING LIGHT
Light is the foundational element in photography – both scientifically and artistically – because it directly determines exposure, contrast, colour rendition, and image detail.
Technically, photography is the recording of light reflected from a subject, captured by a photosensitive surface such as film or a digital sensor.
Analogy: Light in photography is like oxygen in fire – without it, the image cannot exist. Just as fire reveals its character through flame, photography reveals its story through light.
The intensity (illuminance), direction, quality (hard or soft), and colour temperature of light each influence how a subject appears.
Proper exposure requires balancing three interdependent variables – shutter speed, aperture, and ISO – based on available light.
High dynamic range lighting can create dramatic tonal contrasts, while diffused light minimizes shadows and flatters skin in portraiture.
In low-light situations, longer exposures or higher ISO levels may be necessary but can introduce motion blur or noise. Thus, understanding and manipulating light is essential for controlling mood, clarity, and realism in a photographic composition.
BEYOND THE TECHNICAL
Beyond foot-candles, nits, lumens, colour temperature, and several other technical aspects of light, these elements critically influence photographic outcomes.
Light direction determines the shape and dimensionality of the subject, with side lighting enhancing texture and form, while front lighting tends to flatten features.
Light quality, defined as hard or soft, affects the sharpness of shadows – hard light (from small or distant sources) creates crisp edges, whereas soft light (from large or diffused sources) produces gradual transitions and gentle highlights.
Light intensity distribution, or falloff, dictates how quickly light diminishes over distance, governed by the inverse square law.
Spectral distribution refers to the completeness of wavelengths emitted by a source, which affects how accurately colours are rendered; high-CRI (Colour Rendering Index) lighting is preferred for faithful reproduction.
Polarization and angle of incidence also influence reflectivity, glare, and surface details, especially in product or landscape photography.
Mastering these nuanced elements enables photographers to control tone, depth, mood, and realism with precision.
HOW DO WE MEASURE LIGHT?
The terms foot-candles and nits both measure light, but they do so in very different contexts and units. The change in usage from foot-candles to nits reflects a shift in technology and what we are measuring: illumination (light falling on a surface) vs. luminance (light emitted from a surface).
Foot-Candles (fc)
What it measures: Illuminance – the amount of light falling onto a surface Unit: 1 foot-candle = 1 lumen per square foot.
Use case: Lighting design for rooms, stages, factories, etc.
Legacy: Common in older building codes, photography exposure settings, and architectural lighting standards (especially in the U.S.)
Nits (cd/m²)
What it measures: Luminance – the amount of light emitted or reflected by a surface in a given direction.
Unit: 1 nit = 1 candela per square meter (cd/m²)
Use case: Display brightness (TVs, monitors, phones), HDR standards, visibility under daylight.
Modern use: Standard unit for electronic displays and outdoor readability.
Lumens and Lux
In short, lumens tell you how much light is produced, while lux tells you how much of it is useful where it matters.
Lumens (lm) – Total Light Output
- What it measures: The total amount of visible light emitted by a source, regardless of direction or distance.
- Use case: Used to rate light bulbs, LEDs, and flashlights.
- Analogy: Like saying how much water is coming out of a hose—without caring where it lands.
Lux (lx) – Illuminance on a Surface
- What it measures: How much light actually falls on a surface.
- Unit: 1 lux = 1 lumen per square meter.
- Use case: Used in lighting design to ensure proper brightness in workplaces, schools, studios, etc.
- Analogy: Like saying how wet a square meter of ground gets from the hose—depends on both water volume (lumens) and spread.
Why Did the Change Happen?
Technology Shift: With the rise of digital screens, we care more about how much light a screen emits, not how much hits a surface. That requires luminance, not illuminance.
Metric Standardization: The nit (candela/m²) is part of the SI (metric) system, while the foot-candle is imperial and increasingly phased out globally.
Precision for Displays: Modern HDR displays are rated in nits because it is the best way to convey how visibly bright an image will appear to the human eye.
Analogy: Imagine a flashlight: Foot-candles tell you how much light lands on the wall. Nits tell you how bright the flashlight lens itself looks when you stare at it.
COLOUR TEMPERATURE OF LIGHT
Colour temperature is a physical measurement of the spectral composition of light, expressed in Kelvin (K), which describes whether a light source appears warm (reddish) or cool (bluish).
It is based on the concept of a black-body radiator – an idealized object that emits light when heated. As the black-body’s temperature increases, it glows red, then orange, white, and eventually blue.
Light sources with lower colour temperatures (e.g., 2700K–3000K, like incandescent bulbs or sunrise) emit more red and yellow wavelengths, producing a “warm” appearance. Higher colour temperatures (e.g., 5500K–6500K, like midday sunlight or daylight-balanced LEDs) shift toward blue, creating a “cool” look.
In photography and videography, accurate colour temperature control is critical for proper white balance; mismatched lighting can cause colour casts that distort skin tones or material colours.
Modern digital cameras often use auto white balance (AWB) algorithms or allow manual Kelvin adjustments to compensate for different lighting environments and maintain colour fidelity.
CONCLUSION
Light is not merely a tool in photography – it is the essence of the craft. From its measurable properties like intensity, colour temperature, and luminance, to its more subtle characteristics like direction, quality, and spectral fidelity, light shapes every visual narrative.
A photograph is ultimately a record of how light interacts with a subject at a specific moment in time.
Mastery of lighting transforms an image from a simple capture into a compelling visual story, making technical understanding of light as critical as artistic vision in achieving powerful and expressive photography.
About the Author:
Michael Martin is the Vice President of Technology with Metercor Inc., a Smart Meter, IoT, and Smart City systems integrator based in Canada. He has more than 40 years of experience in systems design for applications that use broadband networks, optical fibre, wireless, and digital communications technologies. He is a business and technology consultant. He was a senior executive consultant for 15 years with IBM, where he worked in the GBS Global Center of Competency for Energy and Utilities and the GTS Global Center of Excellence for Energy and Utilities. He is a founding partner and President of MICAN Communications and before that was President of Comlink Systems Limited and Ensat Broadcast Services, Inc., both divisions of Cygnal Technologies Corporation (CYN: TSX).
Martin served on the Board of Directors for TeraGo Inc (TGO: TSX) and on the Board of Directors for Avante Logixx Inc. (XX: TSX.V). He has served as a Member, SCC ISO-IEC JTC 1/SC-41 – Internet of Things and related technologies, ISO – International Organization for Standardization, and as a member of the NIST SP 500-325 Fog Computing Conceptual Model, National Institute of Standards and Technology. He served on the Board of Governors of the University of Ontario Institute of Technology (UOIT) [now Ontario Tech University] and on the Board of Advisers of five different Colleges in Ontario – Centennial College, Humber College, George Brown College, Durham College, Ryerson Polytechnic University [now Toronto Metropolitan University]. For 16 years he served on the Board of the Society of Motion Picture and Television Engineers (SMPTE), Toronto Section.
He holds three master’s degrees, in business (MBA), communication (MA), and education (MEd). As well, he has three undergraduate diplomas and seven certifications in business, computer programming, internetworking, project management, media, photography, and communication technology. He has completed over 50 next generation MOOC (Massive Open Online Courses) continuous education in a wide variety of topics, including: Economics, Python Programming, Internet of Things, Cloud, Artificial Intelligence and Cognitive systems, Blockchain, Agile, Big Data, Design Thinking, Security, Indigenous Canada awareness, and more.
Very well said!