Stock photography can potentially be a good way to make some extra money off of your images. It's not for everyone, and it's definitely not going to make you rich (unless you're Yuri Arcurs.) But some photographers with a big portfolio and lack of a market can benefit from it. Be aware that there are many controversies behind stock photography, mostly about how they devalue the worth of photographers. So you may want to do a little research before diving in. To get you started, here are four of the biggest stock photography sites and how they work:

Fotolia

This is a quickly growing microstock photography agency that has gone from 4 million images and 800,000 members in 2008 to over 17 million images and 3 million members in 2012. Photos and illustrations are purchased with credits which have a different exchange rate depending on how many credits you buy, but it hovers around the $1=1 credit mark. Subscriptions can also be purchased giving buyers 25 downloads per day. Buying bulk subscription packages means they can purchase an image for as low as $0.19.

They pay rate to the contributor ranges from 20%-63% of the buyer's cost, based on your rank. The more downloads you get, the higher your rank is. For the majority of the plans 1 download=1 download towards you rank, but when buyers are using a subscription plan, 1 download=1/4 download toward your rank. Fotolia also has an exclusivity option where you can receive a larger percentage of the fees for only selling photos on their site, that is, as far as stock photo agencies go. You can still sell images through your own site and do work for clients.

Unlike some other stock agencies, Fotolia also lets your set your own prices for your images within certain parameters. At $50, they also have the lowest payout threshold, meaning the amount you have to make in order to get your money. This site is one of the best for photographers looking to get into stock photography.

iStockphoto

In case you're wondering, iStockphoto is not an agency that only accepts iPhone pictures. It is, however, another well-know microstock agency that sells photos, illustrations, video, audio, and flash files and uses the credit system. Credits costs from $0.95 to $1.50 and the number of credits it costs to buy a photo depends on the size of the image. This can range from 1 to 28 credits. iStockphoto also has pay-as-you-go or monthly plans.

To get in, you must pass a short quiz about general photography knowledge and submit three of your best images. Once the three images are screened and passed, you can upload more photos. Contributors receive 15% starting off which can be bumped up to a maximum of 45% depending on the number of downloads the contributor has and if he/she has opted into the exclusivity option. Unlike Fotolia, being exclusive to iStockphoto has requirements. You must have 250 downloads and a 50% photo approval rating to be eligible.

While the pay split is lower than other stock photo sites, iStockphoto has the advantage of size and reputation. It is one of the most well-known stock agencies and has one of the best search engines which can even translate keywords into other languages. Payout threshold is $100.

Getty Images

Getty is the stock photo monster. Check the Yahoo front page. Chances are that at least one of the photos there is from Getty. Their main business is in celebrity, sports, and photojournalism images. They're the big players and are more selective about who they work with. This is probably not the best place to start if you're thinking of entering the stock photography world.

But, if you want to try, the easiest way to get in is to submit your 12 best images in Getty Images Call for Artists Group on Flickr and wait for response. Don't expect for them to get back to you in the next few days though. They have a lot of photographers to screen, so it will take some time.

Unlike Fotolia and iStockphoto, Getty is not a microstock agency. They have royalty-free images ranging from $26-$600 of which contributors receive 20%, and rights-managed photos around $500-$600 of which you get 30-40%. Again, the percentages are lower, but you are being paid in bigger chunks.

Shutterstock

Shutterstock is the largest subscription-based stock photo agency in the world. In June of 2012, they surpassed the 20 million mark in terms of downloadable images. Their most popular plan is the 25-a-day download subscription which costs $249 a month.

To get in, you need to fill out an application, pass identification using a government issued ID, and submit 10 images for screening. Seven of the ten images must be approved to gain contributor status. If you fail, you must wait 30 days to resubmit. Don't be put down if you don't make it. Shutterstock has one of the most rigid screening processes and many have complained about their low acceptance rate. But this goes to insure good quality in their photo library. If you do fail the approval process, there is a critique forum full of other stock photographers who can help you figure out why your images didn't make it in.

For every one of your photos downloaded you receive $0.25-$0.38 from per-day-subscribers, $0.81-$2.85 for On-Demand subscribers, and $28.00 for enhanced licensed images. You will earn more after reaching certain lifetime earnings milestones. You can also get small bonuses for referring other contributors to the site. Payout threshold is $75.

Shutterstock's advantages (besides being the biggest agency) include facebook and twitter applications that let you promote your work. They also have tutorial designed to help you get the most out of your keywords.

Also Read: 23 THINGS YOU MUST KNOW TO BE SUCCESSFUL IN PHOTOGRAPHY

Recommended Reading:

• 2013 Photographer's Market: The Most Trusted Guide to Selling Your Photography
• Best Business Practices for Photographers
• The Fast Track Photographer Business Plan: Build a Successful Photography Venture from the Ground Up
• Group Portrait Photography Handbook
• The Best of Family Portrait Photography: Professional Techniques and Images
• 500 Poses for Photographing Group Portraits
• Selling Your Photography: How to Make Money in New and Traditional Markets 
• Starting Your Career as a Freelance Photographer
• Photographer's Survival Manual: A Legal Guide for Artists in the Digital Age
• Legal Handbook for Photographers: The Rights and Liabilities of Making Images
• Taking Stock: Make money in microstock creating photos that sell
• Going Pro: How to Make the Leap from Aspiring to Professional Photographer

Image credit: stylephotographs / 123RF Stock Photo

Written by Spencer Seastrom