Ben's Techno-Babble Decoder Ring
Chromatic aberration: An effect that causes small halos of different colors on the edges of objects. This happens when a lens focuses different colors of light in different places on the image.
Luminance: Another word for brightness. When someone talks about the luminance of an image, they usually ignore all issues relating to color and just concentrate on what's happening to the brightness of the image.
RAW file format: A special file format that contains the raw data that was captured with a digital camera's sensor. This unadulterated information gives you the most versatility when opening an image in Photoshop. Unlike the other file formats available (like JPEG and TIFF), RAW files allow you to change important settings like White Balance at the time you open the image. JPEG and TIFF images have those settings locked into the image so they can't easily be changed after the photo is taken.
Vignetting: Darkening of the corners and edges of an image due to light falloff in the lens of the camera.