Three things to consider when it comes to lighting: The light source, the type of light, and the fixture holding the bulb. The effects and the results of combining these three things can vary immensely. An overview.

1.   Point light vs. linear light

The light sources can be divided into point light and linear light. A point light gives contrast and creates helpful shadows where it enhances structures. A linear light gives diffuse lighting which can be helpful for certain tasks as it eliminates shadows. The difference between the two would be best explained by imagining an indoor brick wall, which comes to live with a grazing halogen spot light, and becomes dull under a set of fluorescent tubes.

The sun is a point light source, and an overcast sky a diffuse light source. On a sunny day, the point light component of the sun accounts for 20% of the total light level, and the rest is made up of diffused lighting. A city’s architecture looks nicer on a sunny day. On a ski slope, direct sunlight gives contrast on the piste, whereas an overcast sky obliterates all contrast, making little hills and mounds all but unnoticeable.

A halogen spot is a point light source, and a fluorescent tube or a compact fluorescent bulb is a linear light source. Only stage lighting is almost exclusively point lighting and is primarily intended to create illusions. Architectural lighting sometimes adopts stage lighting methods such as stark contrasts: Spot lights to enhance objects. A standard incandescent bulb is somewhere between the two since the fixture holding the bulb is often a decorative light fixture, creating soft diffuse lighting. Also, all lit surfaces reflect light, and that adds to the diffuse component.

2.   Types of light
The types of light have an effect on color temperature (such as warm, reddish light, or cold, white light), color rendering index, or CRI, which is the ability to see true colors under the light source, and the level of brightness.

Human beings are affected by the color temperature. There are office lighting systems that are whiter during day time, and become warmer in the late afternoon, thus resembling the sunset which matches the biological clock.

3.   The fixture
Divided into decorative, architectural, outdoor, and specialty lighting. Decorative lighting is where the lighting fixture is an object of art, a well-designed piece of furniture that provides illumination and enhances the decoration. The Artemide Tizio self-balancing desk lamp earned itself a spot in the New York Museum of Modern Art and is one of the most practical desk lamps available.

Architectural lighting provides light, but you should not be able see the source under normal circumstances. Oftentimes, with cheaper light fixtures, the light source or the reflector causes glare. There is an enormous variety and a great many brands and manufacturers when it comes to architectural lighting, and so selecting the right product for your project is something best done by specialists. There’s a great difference between a professionally designed space and a lighting design by a layman.

Outdoor lighting leaves no room for compromises regarding quality. Good outdoor lighting is expensive, and will last a very long time. Anything less, will last for a few months, after which there is algae on the inside of the glass of the spotlight, the in-ground uplight sucked up water and fails, or the painting of the bollard peels off under the sun.

About lamps

Color temperature - general
The color of the light is important. It varies from warm to cool; whereas warm is a reddish-yellowish color, and cool is very white. Photographers like to take pictures just before sunset (referred to as the “magical hours”) as the color temperature becomes warmer and colors are more enhanced. Candle light is reddish and called very warm, incandescent lamps are warm white, and fluorescent lamps vary from cool daylight to daylight to warm. Color temperature has a strong effect on indoor ambience and the biological clock of people.

Color temperature - technical
A characteristic of visible light. Expressed in Kelvin (K), whereas Kelvin equals degrees Celsius + 273. A theoretical black body radiator heated up to 1200K emits a light similar to candle light, heated up to 3000K it emits light comparable with halogen, and heated up to 6000K its color temperature is similar to that of an overcast sky. Note that the expressions “warm” and “cool” are merely indicative; in fact the higher the color temperature, the greater the heat of the black body radiator.

Color temperature - an overview

Color Rendering Index - general
Almost every light source emits white light, which is made up of the full spectrum, or all the colors of the rainbow. Fluorescent lighting is more bluish, because it emits very little red light. Incandescent lighting is more yellowish/reddish, because it emits less blue light. Hence, a blue shirt will look different at home under normal lighting (viz. less blue), compared with in the store under fluorescent lamps (viz. deeper, richer blue). It is the opposite for a red color shirt: That would look almost grey under fluorescent lamps.

Color Rendering Index - technical
A measure of how closely a light source renders colors accurately on a scale of 0-100. CRI is an indicator of the relative color rendering ability of a source and should only be used as such.

Color Rendering Index - an overview

Software

DIALux is the most widely used software for lighting planning and is use the world over by lighting designers. The indoor and outdoor areas can be recreated on a computer and lighting fixtures can be added or moved to different locations. By importing data such as the light output of the fixtures (so-called IES files, comprising of the power, the intensity and luminous flow, luminance diagrams, and isolux photometric curves of the fixture), and entering the reflective properties of the surfaces, a certain lux or brightness level will be calculated. DIALux can be used for different environments to calculate the components of ambient, accent, and task lighting.