There is an old saying that a photograph is worth 1000 words. I suggest that photographs are probably worth much more than 1000 words but that does not mean that the information is accurate or correct. I have put up notice that most genealogists accept photographs on their face totally and uncritically. A photograph is a source, just like any other source, and is subject to the same requirements of evaluation concerning reliability as any other source.
Let me give a hypothetical situation. Suppose that family members who have been bitterly fighting with each other throughout their lives all all come to the same funeral. A photograph taken at the funeral may show a happily smiling family group but would be utterly misleading as to the relationships between the parties. Further, the backgrounds and style of the photographs may be entirely misleading. Some of the very old photographs required long exposures and those photographs seldom, if ever, showed that individuals smiling. In one series of photos I found in an old collection, the women in different photos shared the same dress. Without seeing the related photographs, it would be impossible to know this fact. You may consider some of these examples to be trivial but we all have a tendency to identify our ancestors with their photographs.
I am not arguing that photographs are not useful in contributing historic information concerning ancestors. What I am saying is that photographs can be just as inaccurate or misleading as any other documentary source. The first important fact to realize is that the photographer chooses the subject matter, place and timing of the photograph. It is entirely possible for the photographer to frame the photo so as to cut it out what to the photographer are undesirable background objects or other people. To the extent that the photograph is controlled by the photographer it is a personal statement taken from the photographer's point of view rather than an objective historical document.
I recently discussed the ethics of altering existing historical photographs when making copies. There is a more serious issue about the process the photographer goes through in selecting and creating a photograph. One of the most famous photographers of our time is Ansell Adams. You might be surprised to know that he spent a great deal of time in the darkroom altering his original photographs. Today, we would call this photoshopping the image. If you have the opportunity to stand next to a gifted photographer and watch that person take photographs and then later, have the opportunity to view the same printed photographs, you may wonder whether or not you were actually present when the photographs were taken.
For this reason, most photographs are notable for what they do not show rather than what they do show. Sometimes photographs suggest relationships and activities that are entirely inconsistent with the traditional family story about the individual ancestor. For example, there may be photographs showing the ancestor enjoying the companionship of someone who was obviously not their spouse or in other situations showing activities that the ancestor would not normally be associated with. In some instances, these types of photographs were destroyed either by the ancestor or by close relatives who did not wish to show the ancestor in a negative light. Occasionally, some of these photos survive to create interesting historical issues.
At one point in the past a photograph could be used as conclusive evidence in a court case. However, that day has long since passed. Today, even with substantial supporting testimony photographs are always subject to a measure of skepticism.
In our modern age, I would guess that there is not one photograph that you can presently see in an advertisement that has not been altered in some way from the original. We are so used to seeing altered photographs that we do not even realize that some of them are so altered as to be totally imaginary.
As genealogists, we may make the mistake to believe that this process of altering photos originated with computers. In fact, since the first photo was taken the photographer has always been in control of the photograph both at the time was taken and during the developing and printing process.
It is always a good idea to take the time to critically evaluate each and every historical photograph. Not only may there be interesting information you may have missed with a superficial examination, there may also be inaccurate or incorrect traditional assumptions about the subjects of the photos that are questioned by the examination.