Light quality is an important factor in photography, essential for creating well balanced and visually impressive images. The winter months tend to produce days where the dark overcast sky and winter light can hinder taking photographs but there are a few ways of getting around the problems caused by poor light.
The first is to simply use a higher speed of ISO(ASA) in the camera. The higher the ISO, the higher the level of contrast and it's image contrast that's needed in any poorly lit situation. The trade off is in grain/noise that can be distracting for some people and in many cases even a fast speed will not produce the results required.
The second solution is the most popular one; to use a flashgun to illuminate a scene. I've used this technique along with the natural lit source in a fill-in flash role - quite simply the flashgun helps light the subject but it is balanced against the natural light source. This is most obviously used by press and PR photographers who use flash to create well illuminated image - essential for photographing people or events and for good quality reproduction in print. Sports photographers also use the fill-in flash technique to freeze the action, using the high speed flash of light to freeze any fast movement.
I've used lots of fill-in flash for two projects; the first was the Rally of Britain ( see top image) and the second can be seen in the speedway gallery. Both required a flashgun as a light source due to fading light caused by poor weather. These projects were done using film but digital now offers a preview facility to check out all shot images and adjust to changing lighting conditions. The photography is only limited by the output power of your flashgun which is usually around the 35 metres/ISO100 mark depending on the make and model.
Part II of this post will look at what sort of flashgun you need, how to use it for fill-in flash and how flash can be used to produce images like the rally photo above.