Royalty-free stock photography offers a photo buyer the ability to use an image in an unlimited number of ways for a single license fee. The client may, however, request "exclusive" rights, preventing other customers from using the same image for a specified length of time or in the same industry. Such sales can command many thousands of dollars, both because they tend to be high-exposure and because the agency is gambling that the image would not have made more money had it remained in circulation. However, with royalty free licensing there is no option for getting exclusive usage rights.
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Roba Al-Assi , Brand and Communications Director , Bayt.com
From my experience as a designer, aside from the large corporations, most companies in the Middle East don't have a large budget to spend on photography. Yet, there is also a huge dearth of culture- and region- relevant stock photography. So, when I am looking for stock photos of a Middle Eastern-looking person, I have a very hard time finding one, so there is definitely need. Maybe something similar to iStockPhoto but with local flavour?
From a financal point of view, it seems like you need to do a feasibility study. Here's a good link about that: http://www.umanitoba.ca/afs/agric_economics/MRAC/feasibility.html
A few years ago, there were a tonne of stock-photo libraries. Then a man by the name of Getty who happened to have a bajillion dollars, thought he'd buy out everyone else and consolidate the business under one name. If he was hoping for a monopoly, then he sure didn't get it. Not long after, new stock-photo libraries started coming out of the woodwork, presumably the old ones under a new name. If that fact has any bearing on your question, then I would say stock-photo-libraries are very commercially viable.
If you're a lone photographer, you may want to consign with established outfits first to multiply your feasible income. If you're the one thinking of starting a library, then by all means, go for it. And best of luck to you.
