Stock photography varies.
Some directories will now only accept the very best photographs that are more creative and totally different to everything else currently on their books.
Others will not be so fussy and just want to get hold of as many stock photographs to sell as possible.
Where do you come in then? Well you need to match up your photograph portfolio to the various directories that are available to sell the pictures for you.
If you are a fantastic photographer then you can work with the best directories about, maybe even selling your reject photographs through the lower quality directories that the not so good photographers are using.
Why use a directory? This is quite a simple question to answer - because they have traffic! Yes, they have a lot of competition already for their searches and what they are selling, but if you are imaginative with your subject and careful with your keywords, you stand a chance of some of your pictures appearing in search results and if they are good enough, then someone will start downloading them.
How you earn The amount and exact policy will earn from one directory to the next, but basically every time someone has the need of a photograph and decides that your photograph fits the bill they download it from the directory.
You then earn a percentage of the price that they are paying for this download.
Exclusivity Most of the stock photograph directories about will also pay you a lot more if you keep your photographs exclusive to them.
Doing so reduces competition, so they like this.
But that does not need to hinder you if you are working with multiple directories.
If you take a handful of shots of the same subject and then select a few suitable photographs you simply upload some to one directory and the rest to the other.
This way all of your work is on offer, whilst not filling one directory with too many similar shots! Taking photos Sorry, but holiday snap shots are unlikely to be accepted by any directory and if there is anybody in the picture, then you will need a signed release by that person to say you can use the photograph, unless it is impossible to identify them from the picture.
Also, photos of brand labels and trademarks are almost certainly not going to be accepted.
Photos from your phone will also probably fail even the basic quality checks, you need to be taking well thought out pictures on a really high resolution camera.
Do remember at this point that the bigger the picture will go the more someone might pay for it, especially as they might want to crop the end result.
Where might the pictures be used? From website designers wanting a stock picture to newspapers wanting to brighten up a news story, I've seen pictures that I know are stock photographs appearing all over the place.
If your images are good, they could be used almost anywhere!