Photography terms starting with R

Rack Focus Motion, Video & Creative Techniques seconds Shifting focus from one subject to another during a shot, moving the viewer's attention deliberately.

Radial Filter Post-Processing & Retouching % A local adjustment applied within or outside an elliptical area, with a feathered edge.

Radio Trigger Lighting & Flash m (range) A transmitter on the camera and receivers on the flashes that fire them by radio signal.

RAID Files, Metadata & Workflow An array of drives configured for redundancy, speed or both, presented to the system as a single volume.

Range Mask Post-Processing & Retouching A refinement that limits a local adjustment to pixels within a specified colour, luminance or depth range.

Rangefinder Camera Cameras, Formats & Systems A camera focused by aligning two images in a coupled optical system, viewed through a bright-line finder separate from the lens.

Raster Image Processor Printing, Display & Output Software that converts an image into the precise droplet pattern a printer lays down, replacing the standard driver.

Raw Bit Depth Sensors & Digital Capture bits The number of bits used to record each photosite's value in a raw file, determining how many tonal levels are captured. Levels = 2^bits

Raw Conversion Post-Processing & Retouching The process of turning a camera's raw sensor data into a viewable image by applying demosaicing, white balance, colour profile and tone rendering.

Raw Data Sensors & Digital Capture ADU The minimally processed values read from the sensor, before demosaicing, white balance or tone rendering.

Raw File Format Files, Metadata & Workflow MB A camera-specific file holding minimally processed sensor data together with the metadata needed to interpret it.

Raw Video Motion, Video & Creative Techniques MB/s Video recorded as minimally processed sensor data, with white balance, colour and tone left adjustable afterwards.

Read Noise Sensors & Digital Capture e⁻ (electrons) Noise introduced by the process of reading and digitising the sensor's signal, independent of how much light was captured.

Readout Speed Sensors & Digital Capture ms How quickly a sensor's entire array can be transferred off the chip, usually quoted as the time to scan the full frame.

Rear-curtain Sync Lighting & Flash A setting that fires the flash at the end of the exposure rather than the beginning, so motion trails follow the subject rather than preceding it.

Rec. 2020 Colour & Colour Management The very wide colour space defined for ultra-high-definition television and high dynamic range delivery.

Rec. 709 Colour & Colour Management The colour space and transfer function standard for high-definition television, sharing its primaries with sRGB.

Reciprocal Rule Exposure & Metering seconds A handholding guideline stating that the slowest safe shutter speed is roughly one over the focal length in use. t ≤ 1 / (focal length × crop factor)

Reciprocity Failure Film, Darkroom & Historic Processes seconds The breakdown of the reciprocity law at very long or very short exposures, where film needs more light than calculation predicts. t_corrected = t^p

Reciprocity Law Exposure & Metering lux-seconds (lx·s) The principle that exposure depends only on the product of light intensity and time, so halving one and doubling the other leaves the result unchanged. H = E × t

Recycle Time Lighting & Flash seconds The interval a flash needs to recharge its capacitor to full power after firing.

Reflected-light Metering Exposure & Metering EV Measuring the light bouncing off a subject toward the camera, which is what every built-in camera meter does.

Reflection Photography Motion, Video & Creative Techniques Using reflective surfaces — water, glass, metal, screens — as a compositional device rather than a nuisance.

Reflector Lighting & Flash stops A panel that bounces existing light back into the shadows, adding fill without a second light source.

Terms starting with R