Tag Archives: Light intensity

Light intensity – estimating the light you need

Light intensity is about finding the natural look

• Computer user •
Get familiar with light intensity. Look for the right light intensity in every shot. It is not always easy – here’s how.

Aim for a light intensity that suites the subject.

When using artificial lights think about how light best suits the subject. Learners often use lights set too bright. We will explore the use of distance to reduce the light intensity.

What is light intensity

You might describe light intensity as the power that light has at a given place. A light is most powerful at its source. As it radiates away from the source it becomes less intense. Actually the light radiated still has the same total energy. As it gets further from the light source it is just spread out more.

At each point where you measure light travelling away from the source there will be less and less light. This is because the total light is more and more spread out. This relationship is called the Inverse Square Law. It is a bit of math which describes how light behaves. For our purposes we just need to know that as the distance from a light increases, the illuminated area also gets larger. The same amount of energy is spread out over a larger area. We can say this in a simple way…

As you move away from a light, the light intensity reduces by “distance squared”.

A camera only samples a small area of light. If the light is spreading out the amount of light it can gather is getting less. The light intensity it can capture reduces with distance. Less light is going to get into the camera.

So the light intensity gets less with distance?

At one meter from the light you can say light intensity is one unit. At two meters the light is spread out over four square meters (1 divided by four). If you take a photo you will get one quarter of the light entering your camera. Here is a table that shows how this goes…

1 M from source :: Light intensity per square meter = 1
2 M from source :: Light intensity per square meter = 1/4
3 M from source :: Light intensity per square meter = 1/9
4 M from source :: Light intensity per square meter = 1/16
and so on…
[M = Meter]

Here is a diagram showing how light intensity falls off according to the inverse square law.

How does this help?

When using artificial light of any kind you should remember light intensity. Good light should match the scene for a good image. It should look natural and the right sort of light (colour, intensity, etc). You also need to have enough illumination for the shot. Too little and the picture will be under exposed. Too much? The picture will be washed out, over exposed. All simple enough.

You need to know that light intensity falls off with the square of the distance for one reason. If you take a picture close to a light (1m) that may be bright enough to achieve what you need. If you move to three meters the light intensity will be reduced to one ninth of its previous amount. That is very different light to use. It changes your light levels in the scene. It will also affect your cameras ability to make an exposure. It may affect the colour of the light or other properties.

For someone using a flash on a camera it works the other way around. If you move to three meters from your subject the flash will light them at one ninth of the light intensity of a shot taken from one meter. They will appear much less bright.

Moving close to or away from a light source

The point is simple. Light intensity determines both the illumination and the brightness of a subject. You don’t need to move a lamp or flash very far for a significant loss (or gain) of light intensity. So guessing where to take your next shot is made easier. You can predict that fall-off now you know how the lighting behaves.

Now you can control your flash two ways. You can turn it down using the menus on your camera (check your manual). Alternatively you can move back. Even a short distance back will reduce the brightness of the shot by a lot.

Next time you are using a flash…

Why not test the theory. Put your camera in manual mode. Take a picture at one meter. Without changing the settings, move back. Try two meters, then three, and so on. Each picture will get dimmer. Quicker than you expect you will not be able to make an exposure. This is probably one of the most important lessons about the behaviour of light.

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Twelve Simple tips for atmospheric candlelight shots

Candles put out a wonderful light…

Everyone feels the atmospheric impact of candlelight. The colour and the low light seems to draw you in. Capturing that light is easy with a few simple hints. Lets look at what is needed…

Tripod…

There is nearly always low light associated with candle photography. That means working with longer exposures. A tripod is excellent for that. Indoors, beware of a wooden floor, any move you make can be transferred to the tripod. Floor vibrations can ruin a shot or make it soft. For sharpness remember to use the camera timer for the shot or a remote shutter release.

Lighting…

The best way to view candles is by their own light. Because they don’t use a tripod many people are tempted to use flash. Unfortunately flash will over-power the candlelight. It will take out the colour from the light and tend to create hard, sharp shadows. It will ruin the atmosphere of the candlelight. Make sure you switch off your flash. If you need more light the you can use as many candles as you need to raise light levels. They don’t need to be in the shot, but they will keep the light the same throughout the shot.

Composition…

First decide if your candle or candles are the subject or are props. This decision will affect your focus and how you lay out your scene. Candles can create a strong bright spot in the scene. If it is too bright the flame will form a burnt out white spot. Once you have arranged your scene, ensure that the candle will only draw the eye a small amount unless it is the subject. You should consider the placement of the candle in a way that might minimise the impact of the bright flame spot.

Positioning…

If all your candles are close together the light will tend to act as one light source. This will tend to act as a hard light creating more defined shadows. If you want the light to be softer and the shadows with less well defined edges set your candles further apart. If the light is to be cast on a face then soft light will be more flattering.

Movement…

One of the peculiarities of working with candles is that the flames are subject to the slightest air movement. Unfortunately candle flicker is attractive to the eye in real-time; but looks like a loss of sharpness in a still image. It is quite useful in close focus shots with a candle to use an air break of some kind nearby to stop air movement. In a table-top study use a large sheet of card to one side out of shot. That will help prevent air movements. If not, keep an eye on the flames when shooting. Try to capture the flame upright or, if using more than one flame, make sure they are all going the same way. They look more natural that way.

Since candle light is low intensity, make sure you also prevent other sources of movement in the shot. They will inevitably be blurred as the shot will be using a long exposure. This will look like a distraction against still flames.

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Light intensity…

The light from a candle can be made much more intense if you use something to catch the light from the candle. A face, hand or other objects bring alive the picture and complements the candle. The presence of the object acts to reflect the candlelight. Light flesh tones are particularly good in this respect since the flesh colour is tonally close to the candlelight hues and they act as a reflector to bring out the light.

From

From “Candle Series” by Spicedfish
From “Candle Series” by Spicedfish on Flickr External link - opens new tab/page

Using reflectors in a candle scene is a great way to raise the light intensity. You can find other types of surface than the one in this picture in most scenes. Walls, ceilings and even off-shot reflectors are all good. Be careful to use neutral colours. Colour reflectors will affect the colour of the scene. If you are using a big card out-of-shot make it white. This will reflect the same colour light back into the scene, filling in the light.

Shadows…

The other side of light intensity is the shadows. The darker tones and strong contrasts of candle shots create most of the atmosphere. Spend time studying the shadows created in your scene. Strong contrasts are great subjects. If you create shadows that fall badly across your scene it will impact on the overall effect. The best use of shadows is often to the edges of the shot. If the light fades out to edges this holds the scene into the shot – naturally focusing the eye. Work with shadows to ensure the mood is harmonious.

Additional lights…

If you want to use fill light in the scene try to match the quality of light from your candles. Use soft light sources and natural light with hues matching the candles. Natural light will fill the scene well but tend to neutralise the colour of the candle light. The warm glow of candles is a great mix with evening, low-intensity light.

Some people use light with gels to give a warm glow. Warming gels can also be used with a flash. However, beware the power of flash. The candles will lose their soothing effect if all the shadows are taken away around the base of the candle and harsh shadows are introduced from one side. Typically use a diffused flash on the lowest setting – it also helps to be a distance away from the candles as well.

Multiple candles…

When working with one candle as subject the main focus of the shot is clear. However, there is a lot of scope for creativity. Consider two main issues. How to layout your candles and how to use the overall light with the layout. Using candles for making patterns is great fun and can produce excellent shots.

Patterns with candles

Making patterns with candles
Click to view Google Images “Candle Light” search

Try to keep the scene simple. Overlapping candles or indistinct objects in the pattern are confusing. Work with the sharp contrasts and keep your pattern well defined.

Exposure…

How long should you make your exposure? This depends, like any scene, on your light levels. To get more light in the exposure a long shutter speed is suitable for most candle shots. A range of 1/15 second down to 2 seconds is a good starting range with an ISO of 100. Camera settings vary significantly with reflectors, multiple candles or fill lights. Experiment to get it right. Aim to make the shot moody or atmospheric while providing detail for the eye to look at around the candle flame(s).

The main exposure concern with dark or shadowy shots is digital noise. If ISO is too high you will get more noise. It is better to use a low ISO, say 100 and have longer shutter opening. This reduces noise and means more detail is visible.

Lenses…

A fast lens allows a wider aperture. Faster lenses will allow a quicker exposure than a smaller aperture. Nevertheless, when experimenting check the depth of field. With big candle patterns, or larger subjects, a very wide aperture will give a very shallow depth of field. Too shallow and you will lose a lot of detail. On the other hand, lots of candles in the background with a shallow depth of field will produce pleasing bokeh. For choosing your lens, more than other aspects of your set-up, you need to have a clear vision of what you want your final shot to look like. Then do some “Chimping” to check results.

Prime lenses, especially the 50mm, will give an approximation to the human eyes. To capture the mood of a scene a 50mm will help. A wide angle lens close-up can provide great exaggerations of candle tallness or broadness – depending on lens orientation. There is great scope for artistic interpretation. Also remember that zoom lenses tend to foreshorten, reducing the apparent depth of the shot. With a zoom lens place your candles to give an impression of depth.

White balance…

The warm glow of candles is attractive. If you change the white balance you will change the characteristics of the warm glow. Candlelight shots are about moodiness and atmosphere. It is worth playing with the white balance to influence the shot and increase moodiness, but be careful you don’t remove it. You only need to adjust white balance when shooting in *.jpg as it will be fixed once the shot is taken. If you are shooting in RAW you have more flexibility with settings in post processing to control colours and the final exposure. If you cannot shoot in RAW then, again, make sure you do some “chimping” to get the colours right.

Being safe…

Although fun, candles are naked flames. It is all too easy in low light to leave something close to the candle. Fires start quickly and spread fast too. Feel free to experiment but make sure you don’t accidentally knock over candles, touch wall paper with one or do something else to set off a fire. Never leave candles alight and unattended. Always blow them out and wait for the smoke stop raising before leaving.

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By Damon Guy (author and Photokonnexion editor)

Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photogs.
See also: Editors ‘Bio’.
By Damon Guy see his profile on Google+.