Monday, August 25, 2008

Image Half Life

Quite often I am asked how long a stock image will live. I have always had difficulty answering this question because, while sales from some images diminish rapidly, other images continue to generate sales for over twenty plus years. After some analysis, I came up with a concept of “image half life” to explain the rate at which stock photo income declines over time.

The term “image half life” is borrowed from physics where it refers to the unpredictable life span of a decaying atom. Similarly, in stock photography a body of work will not just stop earning at one point in time. Instead it will probably follow a course whereby it produces steady income for several years and then gradually begins to diminish over time. The rate of diminishing return varies with a number of circumstances – longevity factor of the individual image subject, the agency where the image is placed, changing photographic styles, changes within the stock marketplace, and numerous other factors.

Simply put, image half life in stock photography refers to the period of time over which the sales from a body of stock images will diminish to half of what it was in its first year of marketing. As an example, let’s say we have a body of newly produced images earning $10,000 annually. If in five years the same body of work is earning only $5,000, and five years after that (ten years from initial marketing) earning $2500, then the image half life is 5, for five years.

Why is image half life important? Stock photographers derive income from royalty payments over time. In order to predict income from a body of work in years to come, it is important to factor in image half life. For purposes of planning retirement income, for instance, you need to know how much income can be expected from a body of work receiving diminishing returns over time.

Once you do the calculations, you will find that it only takes a small percentage of new images added annually to the existing portfolio to maintain its consistent income over time.

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