Stock images must be well lit and properly exposed. This makes them useful in the most possible situations. Flat light, bad shadows, and poor exposure are all serious flaws in an image and will not be accepted.
Light comes from a variety of sources – sometimes you can control them and sometimes you cannot and have to work with what you've got. In all cases you need to be away of the light and the kind of images you can create working with it.
These images were taken at the wrong time of day for the season and have harsh shadows, blown out detail, and dull colours.
In the great outdoors available light usually exceeds what your sensor can reproduce, overexposing the image. Weather and seasonal phenomena like snow or fog can fool your camera metering, producing underexposed images.
On-camera flash can produce harsh shadows, blown-out highlights, and generally unpleasant light. If you must use it, find some way to diffuse it.
Always watch your white balance: if your image is yellow or blue where it should be white, your white balance is wrong. This can be corrected if you shoot RAW, but it's always best to get it right in-camera. Be particularly aware in situations with multiple light sources, as each may have a different white balance.
Lighting is a huge subject. Please read this article for more information.
4.0 Quality Standards
6.0 Title, Description & Keywords
8.0 Model & Property Releases