Having derived from the Greek word Phot-Light & graphos-drawing, light drawing should it be called for the significance of radiance in the art of photography.
The Available light source, before moving much into the varieties of Ambient light, it becomes necessary to give a general introduction on how the brilliant use of ambient(available) light can enhance your photography. Here the brightness or the direction of light is almost impossible to adjust and it becomes the role of the photographer to adjust himself according to the orientation of lighting. Most often, Photographers find it difficult to shoot with the available light, they wish to shoot against the light and to achieve this using reflectors or shades whenever necessary.
For studio setups, ambient light is often considered relative to the additional fill light, hence ambiance light is assumed to behave like a key light. To enhance your chances of producing good results, it is advisable to calculate the lighting ratio, which is the relative intensity of available light and the fill light in determining the contrast of your final image.
It should be a rare occurrence when ambient light can produce point light sources. Tight sealed rooms with light windows could produce magnificent point lights to create a stirring drama in the concept of photograph. Moving away from natural light, vehicle lights are beautiful example of point light, it produces interesting circumstances adding more surprises in a photograph when shot against a right subject.
A Cloudy day is the right example for diffused light. Any light which is very soft and is not a direct source from the light source is a diffused one. To explain better, clouds acts as a soft box in diffusing the original light source. Diffused light is fantastic for any kind of photography, no harsh shadows nor deep contrasts, makes this an ideal lighting display for travel and street photography.
I don't think it can be stated enough, how much your light source could change the whole precieved idea; about what you want you photo to come across as or say. Luckly this has a guide for you about ambient, Point, Diffused, back lit and rim, even down to the positioning of light. Go ahead and test them out.