The “observer effect” is a well known term used in several fields of study, including most notably physics and psychology. The basic concept refers to changes that the act of observation will trigger on the phenomenon being observed. In order to observe a subject, some form of interaction has to occur, and that interaction, even if minimal, will affect the state of the observed in some form or another.
My view is that within the field of photography, this effect is ever present in various forms, and can be explored at various levels. The most common examples include the change in attitude within people upon the realisation that a camera is being pointed towards them. Roland Barthes refers to it as the “act of posing” in Camera Lucida - the process where the subjects transform themselves into an image of themselves in advance of being photographed.
Throughout history, photographers have been trying to exploit this effect from one end, and eliminating it from another. This is clearly visible just by analysing the two styles of street photography - some photographers will use short lenses to become part of the action and clearly make their presence noted, while others will use longer lenses in order to avoid as much as possible any interference with the event being photographed.
The concept becomes even more interesting when analysed from different points of view, in different situations, and through the entire photographic process. Ansel Adams mentioned that there are three entities in each photograph - the subject, the photographer and the viewer. Each of these entities may be affected in one way or another by the act of photography. The subject may be affected by the consciousness of being photographed, or possibly even by the sheer presence of the photographer (a theory certainly worth exploring). The photographer is affected by the voyeuristic act, as is the viewer.
Any photographer will state that their attitude towards a subject changes dramatically during the act of photography. In fact, the entire perception of reality takes a different shape during that split second. Something is triggered, maybe it is the that primitive hunting instinct that is re-awakened. All the photographer cares about, at the moment reality becomes that restricted bounding box that is the viewfinder, is to capture the prey and lock them forever into the box. Or as Cartier-Bresson put it, "I'm not all that interested in the subject of photography. Once the picture is in the box, I'm not all that interested in what happens next. Hunters, after all, aren't cooks."
This duality between photography and its primitive counterpart is all too evident even through the most basic of photographic terms - aim, shoot, capture... Photographers are on a hunt for images, and as a hunter are purely focussed on the final goal, on the best timing and placement of the shot. The observation of a potential subject - and indeed reality in its entirety - is a totally different matter when seen through the camera's viewfinder. Some photographers will state that after a while, the "shooting mode" will also start permeating into "real life" and photographers will start looking at their surroundings as though there was a camera permanently attached to their eye. "One doesn't stop seeing. One doesn't stop framing. It doesn't turn off and turn on. It's on all the time," says Annie Leibovitz. In reality the change is still marked, although it becomes foggier with time. The fact remains that the photographer, the interpretation of the subject and reality itself change through the act of observation through a viewfinder.
When looking into the process of photographing conscious subjects, namely humans for the sake of this argument, the entire play of observation, self-consciousness and interaction - or the lack of it - provides a myriad of possibilities for analysis. We can compare different portraiture styles, for example, ranging from 'life captures', to carefully engineered portraits, and all the grey areas in between. It is interesting to compare, within each variety, the effect the photographer has on the subject, and eventually on the final photograph. For example, in Richard Avedon's 'the family' - a series of portraits of the rich and powerful in America - the photographer had no verbal contact with his subjects; only a very strong visual communication and the resulting enhancement of the subject's self-consciousness. The result is a total destruction of the subjects' confidence and power for those few minutes in the photographer's studio, which can be clearly observed in the final product.
One further point of view to be considered is how the subject of a photograph changes through a viewer's observation of the photograph. The act of photography has already changed the subject through decontextualisation, however this change is only complete when interpreted by the viewer.
Viewers observing a photograph will merge the 'truth' - if there ever was one - with their limited point of view, their baggage of experience, emotions, opinions and biases - together with a knowledge of the context within which the photograph was taken and the temporal difference - into their own interpretation of the image. What a viewer sees when observing a photograph inevitably differs somewhat from what the photographer saw at the time the image was captured, and is most certainly not a reflection of the truth. Observation brings interpretation, which in turn brings change.
In the end, individuals will manipulate reality in whichever way suits them best - both consciously and unconsciously. Photographers have the luxury of manipulating the image permanently. They will inevitably add a piece of themselves to the image, capture it and present the result to viewers, who will manipulate the image transitorily and personally, through the addition of a part of their own self into the mix.
The bottom line is that the entire photographic process is affected by observation, consciousness and self-consciousness. In the end, it is difficult to understand whether there is any truth left - although that is also dependent on one's definition of absolute truth, and whether such thing exists at all.