Image Capture
Capture devices and settings
Capture means turning a scene, document, or screen into pixels. Digital cameras use a sensor; megapixels describe sensor output, but more megapixels do not automatically mean better pictures. Optical zoom changes the lens and preserves detail; digital zoom crops and enlarges, reducing quality. Exposure depends on aperture, shutter speed, and ISO; white balance corrects colour casts from different light sources. Scanners need a resolution setting, a colour mode (colour, greyscale, line art), and sometimes descreening for printed originals.
Formats and transfer
Cameras usually save JPEG (processed and compressed) or RAW (unprocessed sensor data, larger, needing conversion). Scanners typically produce JPEG, TIFF, or PNG. Capture metadata such as EXIF records camera, date, exposure, and sometimes location. Transfer images by card reader, cable, or wireless link, and avoid editing the only copy.
Traps: believing digital zoom adds real detail; scanning at extremely high dpi “just in case” and creating unwieldy files; expecting RAW files to open and print identically everywhere; forgetting that scan resolution must be chosen for the final output size.
Worked example: to print a 4 × 6 inch photo at 300 ppi, you need 1200 × 1800 pixels. A 300 ppi scan of the original gives exactly that. To enlarge the same original to 8 × 12 inches at 300 ppi, you need 2400 × 3600 pixels, so scan at 600 ppi. Rule of thumb: scan resolution = target ppi × enlargement factor.