Perhaps you have a business web site. Or you're considering to mail out a thousand postcards, announcing your latest sales offer. A great photo always helps. An appropriate image always increases the response and conversion rates.

But how are you going to find the right image?

In the past I've used the copyright-free public domain photos I found on Wikipedia. If you visit the Wikipedia Commons project you'll see that it's dedicated to images and some of them are in "public domain," i.e., they are copyright-free.

All photos taken and that belong to the U.S. government, for example, are free because (assuming you’re a U.S. citizen) you've already paid for it with your own tax dollars. (And if you’re not a U.S. citizen thank the American taxpayers for subsidizing that.)

That sounds good but does not work all the time. For one thing, your choices are limited.

I've for example found some great free photos regarding NASA and the Space Shuttle. But what if I need the photo of a family sharing some delicious pizza?

It's not easy to find the right free image for your business through such free sources. Since time also has a cost, what starts out as a free search may end up costing you a lot actually.

If you're on a tight budget and you've tried hiring a professional photographer you know that that's not the right solution either.

So enter royalty-free stock photography. These are the membership sites that offer excellent quality stock photos on every imaginable topic for a very reasonable fee. Some actually have a special section for totally free photos as well, offered as an enticer.

You basically purchase a number of credits, let’s say 100 credits for $100. Then you spend your credits to download any photo you like. The larger the photo and higher its resolution, the more credits you pay.

Roughly speaking, it more or less comes down to $1 for an average size photo of web quality (72 dpi).

If let's say you have a 20-page web site, paying $20 for 20 excellent photos is really a bargain you shouldn’t miss.

You can use and publish these photos for your business purposes as many times as you want without paying any royalties each time you use it. (With professional agency photos you pay a separate royalty for each use.)

But there are some restrictions that you should be aware of as well.

For example, you cannot use the photos in a web site template and then sell the template since that counts as "distribution" and not fair use. Again, you cannot re-sell the photos in any shape or form. There is a limit to the number of copies of a brochure or a book that you can print using the photo, etc.

Read carefully the terms and conditions of the stock photo service before you sign up.

Four such sites I can personally recommend are www.dreamstime.com, www.sxc.hu, www.shutterstock.com and www.istockphoto.com (the last two also offer vector drawings) but there are many others out there. Just make a search with keywords "royalty free stock photo".

Dr. Ugur Akinci is a writer and a small-business owner. Among the many web sites he owns is http://www.wonderfultea.com