Exposure and Light
Light has many benefits to our health n happiness. We get serotonin to aid in happiness from sunlight, we see glorious colors that would otherwise be grey, we can read books by lamp light in the winters evening, and light is essential for plant growth in our gardens.
Light is made up of rays of colour in different frequencies. In fact even radio, x-rays, and microwaves are part of that same spectrum. The different colours are most often produced by the reflection of light from the objects. But some things are colourful because the light is refracted, such as prisms, crystals, and other objects. Such is the hummingbirds, butterflies, and certain reptiles. The hummingbird has ‘scales’ that refract the light and produce wonderful colors. This means as the light changes in direction and intensity so does the colour of the hummingbird. Such are the wonders of God’s creation.
As you compose a picture think about the light.
- How is the subject lit?
- Where is the light coming from?
- How bright is the light?
- What is the light source? (the sun is a different color than flash)
- Will the colour or other aspects change with the light?
I took several pictures of humming
birds one summer afternoon
and discovered very different colours by adding fill flash, changing my angle, or changing exposure (how much light was let into the camera). The picture to the right was taken with the fill flash. This decreased the shutter speed and thus the background light that reached the film, so the background is dark. 
The picture on the left was taken a few seconds later, with no fill flash. As you can see you can get very different results when playing with light. When discussing light and photography, one must consider exposure. Exposure is how much light is let into the camera and recorded onto the film or memory card (if it is digital). Exposure is regulated by how long the shutter is open (shutter speed) and/or how open the lense is (aperture = f/stops) when taking the picture. How much exposure is needed is dependent on two factors: light and the sensitivity of the film or memory card (ISO rating).
Film (& digital cameras) can only ‘see’ a certain range of light, far less than our eye. If there are many shades of black and shades of white, such as charcoal on snow, the camera must choose to record either the black’s or the white’s or go in between. Most automatic cameras go in between (For technical readers cameras are set to expose for 18% grey. Scientists and mathematicians determined most scenes when the blacks are compared to the whites = 18% grey, hence the grey card is used for fine tuning pictures. White balance on a digital is a similar idea, but is designed to adjust colour balance, not exposure.)
So practically speaking. When exposing for the highlights of a subject (sunlight on golden hair), you may lose details in the shadows. And visa versa, when exposing for the shadows the highlights are can be washed out. How do you adjust for this? Well if you have a point and shoot camera you can see if you have any exposure compensation settings, as many do.
If you have an SLR you can adjust the f/stops or the exposure compensation setting. Remember to bracket! (take three to five of the same picture at settings just below and above the original). Most SLR cameras have a meter lock feature. So you can lock the meter on a “neutral” subject and recompose and shoot the subject you want. Check your camera’s directions.
Often we are like the film. We can only focus on a limited amount of things at the same time. This is to our benefit. If we are ‘exposing’ for the light, the ‘details’ in the shadows are lost. The light of course is God’s words and blessings. The shadows are the difficulties and trials. We need the trials for character growth, but the ‘details’ are unnecessary to lament. The ‘details’ are often recited for sympathy or excuse of behaviour. So focus on the light and let the details be lost!