Glossary of terms used in image editing.

IMAGE ADJUSTMENTS

Brightness –how bright an image is. Quite often an image needs more brightness
to make up for poor lighting conditions.

Contrast –the difference in tone between light and dark areas of an image.

Intensity - Intensity is a measure of the brightness of the light pixels in an image
compared with the darker mid-tones and dark pixels. An increase in intensity
increases the vividness of whites while maintaining true darks.

Gamma –an adjustment that lets you pick up detail in a low-contrast image
without significantly affecting the shadows or highlights.

Hue –predominant color. Sometimes an image will appear greenish or have a
red tone. Adjusting the hue can correct that.

Saturation -color depth or richness. Adjusting the saturation can make
washed-out colors more vivid.

Lightness -the overall percentage of white in an image. Quite often Hue,
Saturation, and Lightness adjustments are grouped together.

Red Eye –flash photos can sometimes make eye look red. Most image
editors have a way of getting rid of red eye.

Resize –change the overall size of an image. This may—or may not—change
the overall file size.

Resample –apply sophisticated mathematical formulas to alter the size or resolution
of an image. Resampling for size reduces the size of the image while maintaining
resolution. Resampling resolution—usually down—produces a lower resolution
—and smaller file size image. Don’t worry, the program does the math for you.

 OTHER TERMS

Compression –using a mathematical formula to reduce the size of an image file.
The more an image is compressed, the greater the image degradation.

Crop –cutting away parts of an image to reduce image size or to get rid of parts you
don’t want.

DPI –dots per inch. Any digital image is made up of an array
of  colored dots. A higher dpi number means a higher resolution
image.  Changing the dpi up or down can radically change the size
of a file.  For instance if we take a one inch by one inch image
such as at left, and  if it is a 100 dpi image, its size is 100X100
or 10,000 dots or bits. A 200X200 DPI image isn’t twice as big
but 4 times larger; 200X200=40,000 dots or bits. At 300X300
dpi it is 9 times the size of 100x100, or 90,000 dots or bits.
Now if that box were 5”X7”  like a photo print, at 300dpi it consists of  3,150,000 dots
or bits; 3.15 megapixel.

 File –each image is in essence a file; a chunk of data which can be reconstructed
to produce an image.

Image format –the three most used image formats for photos are JPEG (.jpg),
TIFF (.tif), and Bitmap (.bmp). JPEG and TIFF apply varying levels of compression
to an image. Bitmap does not, and produces the largest files.

Mask –a way of keeping certain portions of a picture from being altered.

Megapixel –short for million pixel or million picture elements. The resolution of digital
cameras is measured in megapixels. The higher the number, the higher the resolution—and
the longer the picture takes to send or print.

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