User's Manual

Photomatix Pro User Guide 29
HDR Image Strictly speaking, an HDR image is an intermediary image with 32 bits per color chan-
nel (96 bits per pixel). An HDR image is the result of merging photos of the same
scene taken under dierent exposure settings and stored in special HDR image
format. The 32-bit intermediary HDR image must be processed with tone mapping
for proper display on standard monitors and prints. It has become very common to
dene "HDR image" as the result of processing the 32-bit HDR image with tone map-
ping, i.e. the tone mapped output, but this is not technically correct.
Histogram Histograms represent brightness distribution in digital images. They help evaluate
correct exposure. The y-axis represents the amount of pixels and the x-axis represents
the brightness value.
JPEG A common image le format with two primary strengths – a relatively small le size
and universal compatibility. JPEGs use a lossy compression scheme and should not
be edited and re-saved.
Noise Statistical variations inherent in the sensor system cause noise. Noise is always pres-
ent, but higher sensitivities and smaller sensors usually generate more noise.
Pixel Digital pictures consist of pixels, the smallest units. Each pixel has a color that can be
represented by 8 or 16 bits or as a oating-point number (32bit HDR).
PPI Pixels per Inch. Can be used to describe the actual pixels per inch of a print. Often
confused with DPI (Dots per Inch), used by color printers to print an image.
RAW File A le containing the raw data from the camera sensor. RAW les do not have a color
prole or other stylistic preferences permanently applied.
TIFF A comprehensive image format that oers lossless compression schemes for smaller
le sizes with higher quality. This format is suitable for editing and printing but not
publishing on the Web.
Tone Mapping Processing a 32-bit HDR image into an image that can be properly viewed on
monitors and in prints.