First Thing First, Understanding Light

Every time we take a photograph, we write a diary, a story, a comic or what have you. We do our writing with light, which what the word photography means, writing with light.
If we like to pursue photography as a profession, or as a hobby, the first thing we must do, is to try to understand light. Understanding light will enable us to capture and produce creative, dynamic and spectacular images. There are three properties of light, which as photographers, are important to us, Light Temperature, Light Intensity and Light Direction.

Light Temperature
First, we need to think of light, in terms of having a color temperature, and Forget about it’s other chracteristics such as softness or intensity. This temperature is measured in Kelvin degrees. (Kelvin is similar to the Celsius scale but uses absolute zero, -273 C, as the starting point rather than the freezing temperature of water) Also it is important to know, that light with a lower color temperature is a warmer light and a light with a higher temperature, is a cooler light.
Now, thinking of light color temperature, Tungsten light, regular household electrical bulb, has a temperature of about 3,200 Kelvin or lower. A florescent light has a higher temperature of about 4,000 degree. (In recent years, manufacturers have been making florescent bulbs which give you warmer light, near or, at incandescent light temperature). It's also important to know that, as you dim a light, the temperature drops. The light of a dimmed incandescent Tungsten light for instance, would be less than 3,200 and all the way down to less than 2,000, when dimmed. A candle light is about 1,400-1,900 Kelvin.
Day light temperature varies from about 2,000 K at sunrise and sunsets to about 20,000 in late evening (blue shades!). A flash temperature is to mimic a neutral high noon temperature of about 5,500K. And yes, again, the warmer light has a lower temperature and colder light has a higher temperature!
Now, why is it important to know all this? These are some of the reasons why::

First, let’s have a quick understanding of what camera White Balance is. When you set your camera white balance, you are essentially giving your camera, the temperature of the light that hits the sensor of the camera. According to this information, the camera tries to render all the detail and the colors in the frame, faithfully. Now let’s consider these examples::

In the following photograph, there were 2 sources of light. One source coming from the ceiling light with a temperature of about 3,200 and the second source of light comes from a nearby window, with a temperature range of about 6,000 Degrees K. By setting the white balance to expose for incandescent light or around 3000-3,500 K, we have this chameleon exposed for the warm ceiling light. This exposes the head and shoulders of this already colorful chameleon more correctly, with a warm glow coming from the warm ceiling light. On the right however, we have a light with a 3000 degrees difference, shifting to the blue side which is producing the intense blue tones as seen in the photo.
This is all done with camera and playing with light and not in post processing and playing with software:



Almost everyone would tell you to stay away from mixed lighting and they are generally correct. But when you understand light better, you can actually produce some spectacular colors, just by mixing light of different temperature. In the photo below, 4 different light sources have been used. On the camera right, there was a big screen monitor producing a light of about 5000 degree K. On the top, there was a ceiling lamp of about 3000K. On the left, there was a black light, with a light of about 10,000 K and in the background, the light source was about 3000K. The Photograph was exposed for the light coming from the Monitor. This is why the blue colors on the neck of this Water Dragon exposed more correctly. But on the top of the head and body, we have intensified the warmer colors with about 2,000 degrees shifting to the warmer side. In the back, the temperature difference due to Light fall off, is even more than 2,000 degrees and this is why it is even more exaggerated. On the left however, we have a temperature difference of about 5,000, shifting to the blue side, coming from the black light. I like the results and again, all done with no photoshop tricks::



While we are on the subject, we better briefly discuss Scattered light as well and how we can use that, to our advantage when we take a photograph.
The light from the sun, consists of all colors of rainbow. As it enters Earth’s atmosphere, the air molecules scatter light and they scatter the blue light more than they do the red light. This is why the sky is blue. This blue scattered light exists in the form of Skylight, even on a sunny day but we don’t normally see it with naked eye. But it can be seen in shaded areas and specially with our camera sensors, in form of Blue Shades. For the same reason, in a clear day, the colors of a sunset Is yellow. This is so because at sunsets and sunrises, there is more atmosphere between us and the sun and more of the blue light have been scattered away. If the air is polluted with more particles or with salt water vapors, such as over the seas, the colors of sunset and sunrises will be shifted more to the reds and oranges. The following photograph shows the yellow sunset on a clear cool day with the blue scattered or skylight which can clearly be seen in the shaded areas::




Now, knowing about scattered light, will allow us to take more interesting photographs. In the following example the Frog was sitting in a window with a glass top. From the right, comes the yellow light from the setting sun, From the top however, comes the blue scattered light or skylight which has given us the interesting blue highlights::



Light Intensity
Understanding light intensity is very important In capturing better exposed photographs. To understand light intensity better, we should first discuss Contrast and Contrast Ratio and Dynamic Range (DR). Light contrast is defined as the brightness range in a scene and scenes with high contrast, have higher range of brightness.
Now, Contrast ratio, is the difference between the brightest point and the darkest point in a scene. The scenes with more intense lighting, have higher contrast ratio. So what, you may ask! What does the contrast ratio, have to do with taking a photograph. Well, this is how it goes::
Any device will record and reproduce a certain range of data. Anything far and beyond this range, will simply either not be recorded, or not be reproduced. Human ear for instance will hear sound frequencies between 20HZ and 20,000 HZ. If your home speakers have a frequency response of let’s say 100 HZ to 12,000 Hertz, any possible deep base below 100 HZ and any treble sound above 12,000 HZ will be lost in the playback of your favorite music. Our digital cameras and the human eyes for that matter, work in the same way.
The Human eye, after about 30 minutes of adjusting to a lighting condition, can comfortably see a dynamic range of 20 stops of light, or a contrast ratio of 1,000,000:1(one stop of light is a light intensity that gives a scene a contrast ratio of 2:1. 2 stops of lights is a light intensity that gives a scene a contrast ratio of 4:1, 3 stops of light, is a light intensity that gives a scene a contrast ratio of 8:1…20 stops of light gives a contrast ratio of 2 to the power of 20, which is about 1,000,000). Best digital cameras on the other hand, can record up to 10 stops of light, or a contrast ratio of 1000:1.
So as you can see, there is a big difference between the dynamic range, and shades of light that the human eye can see, and the range of light that a digital camera can record. SO, when we point our cameras to a certain direction and compose our shot, we MUST remember that, what we see is not necessarily what the camera can, and will record. So, if we would like to better expose our photographs, we must move to a certain position, point our cameras in a certain direction, and frame a certain portion of the scene, where there is a range of lights, which our cameras can comfortably handle. And remember, this range of light is about 10 stops, or a contrast ratio of 1000:1. this is what best D-SLR cameras can handle and even less for the Point-and-Shoot cameras. ANYTIME THERE IS MORE DYNAMIC RANGE IN THE SCENE THAN OUR CAMERAS CAN HANDLE, THE EXTRA SHADES OF LIGHT WILL BE LOST IN FORMS OF CLIPPED SHADOWS (SHDOWS WITH NO DETAIL) AND BLOWN OUT HIGHLIGHTS (BRIGHT SPOTS WITH NO DETAIL).
While clipped shadows and blown highlights are both considered to be technical flaws in a photograph, blown highlights are most noticeable and should be avoided as much as possible. One way to reduce loss of data in our photograph, is to shoot in Camera Raw format ( you can start reading about it HERE). When we shoot in JPEG, the tonal curve applied to our photograph, by the camera, will make us further loose data and Dynamic Range. Shooting in Camera Raw format, will preserve more of the Dynamic Range of the original scene and we can also make different exposures of the same file and blend them in photoshop for even more Dynamic Range in our final photograph.

There was more dynamic range in the following scene than any camera could handle. So, it was shot in raw and 2 conversions were made, one for highlights and one for shadows and then, blended in Photoshop::