Page 18 - (DK) Advanced Photography Guide

16 EXPLAINING | CAMERAS

FROM CAPTURE TO STORAGE

When you press the camera shutter button, sensor, and then the shutter closes to
you start a sequence of events that leads to complete the exposure. The light that reached
a photo. First, the shutter inside the camera the sensor is then measured and converted
opens, exposing the digital sensor behind it to into Raw image data. If you’re shooting JPEG,
light. (Some cameras use an electronic shutter, this data is processed and discarded, and the
but the basic principle is the same.) The finished JPEG is saved to the memory card; if
light, reflected from your subject toward you shoot Raw, the image data is processed
the camera, is focused by the lens onto the more lightly before being saved.

DIGITAL SENSORS

An image sensor is an electronic chip that converts BAYER FILTER
light into digital data. The surface of the sensor is
covered in photodetectors, the number of which Individual photodetectors can only detect light levels, not
color. To produce color information, light passes through
determines the camera’s pixel resolution. Image a color filter—red, green, or blue—before it reaches the
sensors are made in a variety of sizes. The smallest photodetector. The filters are arranged in a mosaic of four;
are found in smartphones and compact cameras, the most common arrangement—one red, one blue, and two
while the largest are used in CSC, DSLR, and digital green filters—is known as the Bayer pattern, after its inventor.
medium-format cameras. The size of the image IMAGE SENSOR
sensor influences the final image in a number of
ways, including its ISO (sensitivity to light), dynamic The size of the sensor in a camera is directly related to the
size of its photodetectors. A small sensor with the same
range (see top right), and the crop factor (see p.98) pixel resolution as a larger sensor will need to include smaller
of the lens that is attached to the camera. photodetectors. However, the smaller the photodetectors
on an image sensor, the more the image will suffer from
graininess, and the lower the image’s dynamic range.

KEY TO ANNOTATIONS
1
1 Camera lens
2 Bayer filter
3 Image sensor
4 Photodetectors
5 Analog electronics
6 Analog/digital (A/D) converter
7 Digital image processor
8 Buffer memory
9 Memory card

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