Appendix:Glossary of portrait graphics

Some definitions related to visual portrait.

A

 * ambient light:the available light completely surrounding a subject that is not introduced artificially.


 * aperture:the opening in a camera lens through which light passes; measured in f-stops.

B

 * background:the area behind the subject.


 * background illumination:light that illuminates the background.


 * bit:short for binary digit, which in a computer is the smallest unit of storage.


 * brightness:the relative amount of light areas in an image.

C

 * cast:See Color Balance, Color Cast & Color Correction


 * centering:the orientation of the subject within the frame.


 * color balance:how a color film reproduces the colors of a scene; using the wrong lighting can cause the colors to appear washed out or unnatural.


 * color cast:the overall bias towards one color in a color image.


 * color correction:applying filters which help balance the color rendition of a scene to match the color response of the eye


 * composition:the content and organization of the image that is being captured for the photograph.


 * continuous-tone: an image where like colors in the subject and scene do not change abruptly; the opposite of posterization.


 * contrast:the range of difference in the light to dark areas of an image.

D

 * diffuse lighting:lighting that is low or moderate in contrast, such as on an overcast day.


 * dot:the smallest element that can be printed by a digital printer.

E

 * exposure:in photographic terms is the product of the intensity of light and the time the light is allowed to act on the film, or digital camera sensor. In practical terms, the aperture controls intensity or amount of light and shutter speed controls the time.


 * eye height:the distance from the bottom of a picture to a horizontal line going through both eyes.

F

 * facial features:the makeup or appearance of a subject's face or its parts, including scars, tattoos, etc.


 * facial region illumination:the light that is incident on the subject's face.


 * facial region size:the facial region as measured from the bottom of the chin to the top of the head (including hair).


 * file size:the size of an image in digital photography, measured in kilobytes (KB), megabytes (MB), or gigabytes (GB). File size is proportional to its pixel dimensions; images with more pixels may produce more detail at a given printed size, but they require more disk space to store and are slower to print.


 * film:photographic emulsion coated on a flexible, transparent base that records images or scenes.


 * film speed:the sensitivity of a film to light, indicated by a number such as ISO 100. The higher the number, the more sensitive or faster the film. (ISO stands for International Organization for Standardization)


 * filter:colored piece of glass or other transparent material used over the lens to emphasize, eliminate, or change the color of the entire scene or certain areas within a scene.


 * focal length:the distance between the film and the optical center of the lens when the lens is focused on infinity. The focal length of the lens on most adjustable cameras is marked in millimeters on the lens mount.


 * focus:the adjustment of the distance setting on a lens to define the subject sharply.


 * focus range:the range within which a camera is able to focus on the selected subject; i.e., from 4 feet to infinity.


 * foreground:the area between the camera and the principal subject.

G

 * graininess:the sand-like or granular appearance of an image. Graininess becomes more pronounced with faster film and the degree of enlargement. In digital imaging, graininess may occur as a result of printing an image, the pixel resolution of which is too coarse, or as a result of using a printer with poor dot resolution.


 * grayscale:term used to describe an image that only contains shades of gray

H

 * head orientation:the positioning of the subject's head, specifically positioning the face to the full frontal position, eyes level and open. For those individuals that wear glasses, proper head orientation is crucial in avoiding unwanted glare from glasses.


 * hue:the attribute of colors that allows them to be designated as red, green, blue, or any intermediate combination of these colors.

L

 * lens:one or more pieces of optical glass or similar material designed to collect and focus rays of light to form a sharp image on the film or digital camera sensor.


 * lighting arrangement:the lighting arrangement for subject illumination possibly consisting of several points of balanced illumination; for example, two points of illumination at approximately 45 degrees on either side of the subject's face, the third point placed so as to illuminate the background uniformly.

N

 * negative:the developed film that contains a reversed tone image of the original scene.


 * neutral gray card:a gray test card without any hue, typically of 18% reflectance.


 * neutral white card:a white test card without any hue, typically of 90% reflectance.

O

 * overexposure: to a condition where too much light reaches the film or digital camera sensor, either because it is too bright or has been applied too long, resulting in a very light photograph.

P

 * PPI:short for pixels per inch; the measurement of resolution for displaying or printing digital images.


 * pixel:short for picture element; a single picture element of a digital photo or displayed image. Taken together, all of the millions of pixels form a grid that represents the content of the image.


 * pixelization:the graininess in an image that results when the pixels are too big, relative to the size of the image.


 * positive:the opposite of a negative, an image with the same tonal relationships as those in the original scenes, for example, a finished print.


 * posterization:the effect produced when a photographic image is displayed or printed with too few colors or shades of gray; the opposite of continuous-tone.


 * print: an exposed film picture that is printed on photographic paper, in color or black and white. In digital imaging, a print is the result of printing the digital image on photographic-quality paper stock using a digital printer.


 * printing:producing the final photo of the captured image which should enable fine facial features to be discernable, whether the print results from conventional photographic processes or digital printout.

R

 * RGB:the way that the colors are recorded in digital imaging. A large percentage of the visible spectrum can be represented by mixing red, green and blue (RGB) colored light in various proportions and intensities.


 * reflectance:the light intensity emitted from a surface in a given direction.


 * resolution: a measure of the detail that can be seen in an image; the higher the resolution, the finer the detail that can be seen.

S

 * sRGB: a standard default RGB color space. This is a device-independent color space designed to remove any color-bias from the representation of an image on the specified device.


 * sharpness: whether an image appears to be in focus.


 * subject positioning:the position of the subject with respect to the camera.

T

 * tone: the degree of lightness or darkness in any given area of a photo.

U

 * underexposure: a condition where too little light reaches the film or digital camera sensor, either because the light is not sufficient or it hasn't been applied long enough; it results in a very dark photograph.