Background of photograph is the element, which is considered as a negative space. Background must complement the main subject, and should be selected as per mood of the photograph.
As a part of photograph, background may contain other elements like pattern, texture and color. It can also have shape and form. When these elements play stronger role in composition, it creates a negative impact on the main subject of the photograph, which reduces the pictorial appeal.
This is the reason why commercial shoot for products and fashion is mostly done on plain backdrop. A plain backdrop will eliminate any texture or pattern and only color of the backdrop will remain as an element. It can have an element of shadow, if we want to add some dimensional punch and depth in the photograph.
However, in many case, we need to shoot a subject against available background. This background of photograph can be buildings, trees, busy street or interior of a room. All of them have additional 'built-in' elements like lines, shapes, form and colors. We must take care to avoid or minimize these disturbing elements, so that the main subject is in focus.
One way is to use widest aperture on the lens, so that shallow depth of field will blur the background. However, on a bright day, it may not be possible to use the widest aperture. In such case, we have two options. Option one is to use lowest ISO setting, on which the camera can be set. Other option is to use a neutral density filter to reduce the light.
Yes, we can use both options, but if we cannot, then?
Well, there are few precautions, we must take, so that even if the background of photograph is not smooth, it does not become a disturbing factor.
Easiest option is to change the camera shooting height and angle. By lowering the camera position, we can shoot at higher angle, and can have sky in the background. If we select a bit higher shooting position, we can shoot at lower angle, and then we can have ground or floor as backdrop. In most of case, all problems can be solved, as both, sky or ground are simple backdrop as compared to buildings and traffic. However, if the subject has to be shot at eye level, then take care, that the background is as simple as possible. Select a place, where the background or field has minimum colors. This is how 'riot of colors' can be avoided. Be sure that no dustbin or other dirt is coming in the frame. No pole, lamp post or tree is placed exactly behind the person, which looks like as if it is coming out of the person's head. No overhead wires are running across the composition. Find a spot where there is a plain wall or, a place where there is a uniform texture or pattern as a backdrop.