DEFINITIONS
OPEN COLOUR
Any image that is not monochrome. It includes a monochrome photograph that has been partially toned or had colour added.
CREATIVE SECTION
This is intended to allow the entrants to apply any artistic creativity or manipulation that they wish to an image. The original image must be a photograph taken by the entrant and the creative work or manipulation must be performed by the entrant. Judging will take into account the creative and artistic ideas displayed in the image and the technical skills employed in the creative process.
OPEN MONOCHROME
Any photography containing shades of only one colour. If toning is carried out, it must be over the total photograph - partial toning and/or the addition of one extra colour is not acceptable in a monochrome section.
APS NATURE DEFINITION
Nature photography records all branches of natural history except anthropology and archaeology. This includes all aspects of the physical world, both animate and inanimate, that have not been made or modified by humans. Nature images must convey the truth of the scene that was photographed. A well-informed person should be able to identify the subject of the image and be satisfied that it has been presented honestly and that no unethical practices have been used to control the subject or capture the image. Images that directly or indirectly show any human activity that threatens the life or welfare of a living organism are not allowed. The most important part of a Nature image is the nature story it tells. High technical standards are expected, and the image must look natural. Adding a vignette or blurring the background during processing is not allowed. Objects created by humans, and evidence of human activity, are allowed in Nature images only when they are a necessary part of the Nature story. Photographs of human-created hybrid plants, cultivated plants, feral animals, domesticated animals, human-created hybrid animals and mounted or preserved zoological specimens are not allowed. Images taken with subjects under controlled conditions, such as zoos, are allowed. Controlling live subjects by chilling, anesthetic or any other method of restricting natural movement for the purpose of a photograph is not allowed. No modification that changes the truth of a Nature image is allowed. Images may be cropped but no other technique that removes, adds or moves any part of the image is allowed. Techniques that remove elements added by the camera, such as dust spots, digital noise and lens flare are allowed. Complete conversion of colour images to greyscale monochrome is allowed. Partial conversion, toning and infrared captures or conversions are not allowed. Images of the same subject that are combined in camera, or with software, by focus stacking or exposure blending are allowed. Multiple images with overlapping fields of view that are taken consecutively and combined in camera or with software (image stitching) are allowed.
Further details are available from link below. APS Nature Division: APS Nature Definition