Understanding Light Source
The Flash head depicted above is called a SpeedLight. It can be attached to the camera directly or use off camera to add additional light to a dark environment.
A flash is a device used in photography producing a flash of Artificial Light to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light. Flash refers either to the flash of light itself or to the electronic flash unit discharging the light. Most current flash units are electronic, having evolved from single-use flashbulbs and flammable powders. Flash units are commonly built directly into a camera. Some cameras allow separate flash units to be mounted via a standardized "accessory mount" bracket (Hot Shoe). In professional studio equipment, flashes may be large, standalone units, or studio strobes, powered by special battery packs or connected to power outlet. They are either synchronized (typically 1/200 of a second) with the camera using a flash synchronization cable or radio signal, or are light-triggered, meaning that only one flash unit needs to be synchronized with the camera, and in turn triggers the other units, referred to as slaves.
As photographers we’re always looking for perfect light. And yet, the quality of available light isn’t always ideal. It is rarely perfect. But in using flash wisely, photographer's are able to enhance or over-ride the available light. With careful use of flash, you are more in control of light, and hence the way the photos will look – than if you had just accepted the existing ambient light. Instead of waiting for perfect light, use what you have available, and add flash to make the best of the situation.
To Understand Flash we need to study Light
The study of light will improve your photography faster than the study of photography will improve your photography. You see, working with light is what makes you a photographer–ANYONE can learn to use a camera.
Quantity of light, of course, is how much light is present in a given scene. But what is quality of light?
Quality of Light
In addition to the amount of light, it’s important to consider the quality of light. The worst-kept secret of landscape photographers is the timing when the best light occurs. Often known as the Golden Hour, this is the hour enveloping sunrise and sunset, when the light is diffused, gentle, and vivid. In comparison, afternoon light is harsh and often leaves subjects looking flat. Light can also differ in color and tone. Early morning light tends to take on a cool blue tint, compared to the warm golden glow of a sunset. Weather changes may also bring about different lighting conditions. Overcast skies, for example, can soften and diffuse harsh afternoon light. This is excellent for foliage or street photography, which often benefits from even lighting conditions. Using the best light requires planning and sacrifices on the photographer’s part.
The Qualities of Light are Hardness, Color, & Direction
Hard Light / Soft Light
The concept of softness in lighting is difficult for most self-taught photographers to grasp because it is entirely counter-intuitive; however, with a little explanation, you will see that an understanding of this principle will dramatically change how you use light.
Simply put, the softness of light is the measure of how abruptly the transition is from highlight to shadow on a subject.
A more gradual gradation from bright to dark is soft light.
A more abrupt transition from highlight to shadow is hard light.
Always remember that the power or brightness of the light source has absolutely nothing to do with the softness of the light.
In more scientific terms, this principle is described using the words “umbra” and “penumbra.” You may have heard these words used to describe the lighting conditions during an eclipse or to describe a person’s rights metaphorically, but the same terms apply to photography lighting. The “umbra” denotes an area fully eclipsed by an opaque object. It is the deepest part of a shadow. The “penumbra” is the area of semi-shadow that is only partially blocked by an opaque object and is therefore a lighter shade of gray than the deepest part of the shadow.
Direction of Light
Regardless of their quality, all light sources have a direction, and subjects will look very different depending on whether they are front-lit, side-lit or back-lit.
Front-lit subjects are those that face the light source, and tend to be evenly illuminated without complicated shadows. Because of this, front-lit subjects tend to be the simplest to photograph, especially for landscape, urban, and simple portrait photography. On the flip side, such lighting isn’t as dramatic, and photos can often turn out flat.
Side-lit subjects offer a lot more depth and complexity than front-lit ones, because the combination of light and shadow often creates a sense of three-dimensionality that viewers experience through their own eyes. This is very useful in producing storytelling portraits and landscapes.
Back-lit subjects have their back to the light source, so as the photographer, you’re shooting while facing the light. Backlighting is frequently used by landscape photographers to achieve a wide range of effects. Two of these are silhouettes and flares. Objects become silhouettes when they are thrown into sharp contrast with the light source, usually so that viewer attention is on the light itself.
On the other hand, flares occur when the photographer conscientiously lets part of the light source shine past an object, which would otherwise block its path. This requires careful positioning on the photographer’s part, because without using edges to block the light source, these would-be flares will simply appear as a bright region of light most of the time.
Shadows and Highlights
Last but not least, we come to shadows and highlights. These are regions on your photo that are so dark or bright that they lack any discernible details. In the image below of the Vatican Museum Spiral Ramp, the blue zones represent the shadows, and the red zones represent the highlights. You can compare the two images side-by-side to see the effects of each.
Most photographers avoid too many shadows and highlights, as they can be distracting. But an appropriate amount of shadows and highlights can enhance a photo when employed correctly, so it’s ultimately up to you to make the call.
When evaluating a shot, ask yourself if your attention is inadvertently drawn toward the shadows or highlights. If your answer is yes and this effect is not intentional, then the clipping is an issue and you should readjust your exposure accordingly.
Finally, never let shadows and highlights stop you from attempting a shot — you may be surprised at how it finally turns out!
Color of Light
Color temperature has been described most simply as a method of describing the color characteristics of light, usually either warm (yellowish) or cool (bluish), and measuring it in degrees of Kelvin (°K).
Color temperatures over 5000 K are called cool colors (bluish white), while lower color temperatures (2700–3000 K) are called warm colors (yellowish white through red).
When you are out taking photos, be it outside under the sun and clouds, or inside using lamps or strobes, the light emitted from every light source casts its own hue on the scene. Fluorescent light has a different hue than tungsten, which has a different hue than candlelight, which has a different hue than quartz, which has a different hue than sodium vapor, etc. Many modern LED lights for video and photography feature adjustable hues, or they might be daylight or tungsten balanced out of the box. These hues can either be captured by your camera’s sensor or film, or it can be neutralized with filters or electronics so that the white interior of the cereal bowl, photographed beneath a “warm” incandescent light bulb, still looks white instead of beige.
So the important note here is Color Temperature and White Balance work together to make sure that white is white.
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