Comparison
Contents
This glossary gathers the terms you will come across in the comparison of Sony camera bodies. They follow the vocabulary of Sony's spec sheets, and every acronym is spelled out. The definitions are deliberately simple: they are meant to help you read a spec sheet, not to replace an optics course.
Reading a camera body's name
- α (alpha) - The name of Sony's range of interchangeable-lens cameras (Sony a7 IV is read "alpha 7 IV").
- Reference (ILCE-7M4) - Sony's model code. ILCE stands for Interchangeable Lens Camera E-mount. The number and letter that follow identify the range and the generation (7M4 for the α7 IV).
- α7 - The base range, versatile.
- α7R - R for resolution: the high-resolution range.
- α7S - S for sensitivity: the low-light range, geared to video.
- α7C - C for compact: an α7 sensor in a smaller body.
- α9 - The speed range, for sport and news.
- α1 - The top of the range, combining resolution and speed.
- I, II, III, IV, V, VI - The generation number of the same model: the α7 IV succeeds the α7 III.
The sensor
- Full frame - A sensor of about 36 × 24 mm (35.9 × 23.9 mm for the α7 V), the size of a 24 × 36 film frame. All the camera bodies on this site are full frame.
- CMOS (Complementary Metal-Oxide-Semiconductor) - A sensor technology where each pixel has its own circuits, allowing fast readout and low power consumption. It is the one used by every camera body on the site.
- Exmor - The trade name of the CMOS sensors designed by Sony.
- Megapixels (MP) - The number of pixels on the sensor, in millions. The higher it is, the more you can crop or print large, but each pixel is smaller (see the article on resolution and pixel size).
- Back-illuminated (BSI, Back-Side Illuminated) - A sensor whose circuits sit behind the photosites rather than in front, letting more light through. It is marked by the letter "R" in the sensor's name (Exmor R).
- Stacked sensor (Exmor RS) - A sensor whose readout circuits sit on a separate layer beneath the photosites (R for back-illuminated, S for Stacked). Readout is much faster, which allows high burst rates and limits distortion of fast subjects. Sony describes the α7 V's as "partially stacked": it has fast circuits above and below the sensing layer, and its readout is about 4.5 times faster than the α7 IV's.
- Sensor readout - The time needed to read all the lines of the sensor, in milliseconds (ms). The shorter it is, the less the electronic shutter distorts moving subjects.
- ISO (International Organization for Standardization) - The sensor's sensitivity to light, named after the body that standardised the scale. A high value amplifies the signal (and the noise). The range shown is the native range; the extended range (for example 50–102,400) goes beyond it, at the cost of lower quality.
- Dynamic range (stops) - The gap between shadows and highlights the sensor can record without losing them. Each stop (or EV) doubles the amount of light; the α7 V claims up to 16 stops according to Sony.
- RAW - A "raw" file that keeps all the data from the sensor, for more thorough development on a computer. Lightweight or compressed RAW gives smaller files.
- Image processor (BIONZ) - The chip that processes the image coming from the sensor. BIONZ is Sony's trade name; XR and XR2 denote more recent generations than the BIONZ X. The α7 V's BIONZ XR2 also includes an AI processing unit, used to recognise and track subjects.
- AI (artificial intelligence) - Here, software trained to recognise subjects (faces, animals, vehicles) or to estimate the colour of the light (white balance).
Shutter and burst
- Mechanical shutter - Physical curtains that uncover the sensor. The maximum speed is written as a fraction of a second (1/8000 s).
- Electronic shutter - The sensor itself starts and stops the exposure, with no moving parts: it is silent and faster, but fast subjects can be distorted if the sensor readout is slow.
- Global shutter - The whole sensor is exposed at exactly the same instant, which removes the distortion. Among the camera bodies on the site, only the α9 III has one.
- Burst (fps) - Number of frames per second, in mechanical or electronic mode. You will also see it written "im/s" (images par seconde) on French pages.
- Burst with no viewfinder blackout - The viewfinder keeps showing the live scene during the burst, which helps you follow a subject.
- Flash sync - The maximum speed at which the flash can fire without a black band appearing on the image.
Stabilisation and autofocus
- Sensor stabilisation (IBIS, In-Body Image Stabilization) - The sensor moves to compensate for your hand shake, on five axes (Sony calls it five-axis optical stabilisation). It is measured in stops (or EV): each stop gained lets you double the exposure time without blur.
- Centre and edge stabilisation - Two stabilisation values: at the centre of the image (up to 7.5 stops for the α7 V) and at the edges (up to 6.5 stops), where it is less effective.
- EV (Exposure Value) and IL (indice de lumination) - Two names, in English and in French, for the same brightness scale, where each step doubles or halves the light.
- AF (autofocus) - Automatic focusing.
- Phase-detection autofocus (PDAF, Phase Detection Auto Focus) - The camera measures directly how far and in which direction the focus needs to be corrected, which makes it fast and effective for following a moving subject. The points are placed on the sensor (the "focal plane").
- Contrast-detection autofocus - The camera looks for the point where the image has the most contrast. It is slower but very precise; it complements phase detection.
- AF-S and AF-C - Autofocus modes: S for Single (one focus, for still subjects) and C for Continuous (focus that follows the subject).
- AF points and coverage - The number of focus points (759 for the α7 V), and the share of the image they cover (about 94%).
- Real-time subject recognition (AI) - The camera identifies a human, an animal, a bird, an insect, a car, a train or a plane, and keeps focus on it even if it moves. Recognition of the eyes, the head and the body posture makes tracking more reliable.
- Autofocus sensitivity (EV) - The lowest brightness at which autofocus works. The lower the value (-4 EV for the α7 V), the better it works in dim light.
Viewfinder and screen
- Electronic viewfinder (EVF, Electronic ViewFinder) - A small screen you look at through the eyecup. Its resolution is measured in millions of dots (Mdots), and its magnification indicates the apparent size of the image (the closer to 1, the larger the image).
- OLED (Organic Light-Emitting Diode) - A screen technology where each dot produces its own light, for deep blacks and good contrast. It is the one used in recent Sony viewfinders.
- Viewfinder refresh rate (Hz, hertz) - The number of images displayed per second (60, 120 or 240 Hz depending on the model). The higher it is, the smoother the tracking of a fast subject. On the α7 V, you choose between "Standard" (60 fps) and "High" (120 fps).
- Touchscreen LCD (Liquid Crystal Display) - A liquid-crystal screen on the back of the camera. Its size is measured in inches and its resolution in millions of dots.
- Tilting, flip-out or four-axis screen - A tilting screen flips up or down, a flip-out screen opens to the side, and a four-axis screen combines both.
Video
- Full HD, 4K and 8K - Video resolutions of about 2,000, 4,000 and 8,000 pixels wide. They are followed by the frame rate.
- 24p, 30p, 60p, 120p - Frames per second, the "p" meaning progressive (each frame is recorded in full). A high frame rate allows slow motion.
- 8-bit, 10-bit - The fineness of colour coding. 10-bit gives more room for colour grading.
- 4:2:0 and 4:2:2 - The amount of colour information kept. 4:2:2 is richer and better suited to grading.
- Oversampling - The video is calculated from a higher resolution (for example 7K to produce 4K), which gives more detail.
- Crop (Super 35) - The video uses only part of the sensor, which lengthens the lens's apparent focal length. Super 35 refers to a sensor size smaller than full frame, inherited from cinema.
- Long GOP and All-Intra - Two ways of compressing video. Long GOP (Group Of Pictures) gives lighter files, All-Intra keeps every frame complete and is easier to edit.
- S&Q (Slow & Quick) - Slow-motion and fast-motion mode.
Cards and connectivity
- SD (Secure Digital) - Standard memory card. UHS-I and UHS-II (Ultra High Speed) are two speed levels, the second being faster.
- CFexpress Type A (Compact Fast express) - An even faster card, the size of an SD card. Several camera bodies have two slots, used to spread or duplicate recordings.
- Memory Stick - Sony's old card format, found on the first models.
- USB (Universal Serial Bus) - Port for file transfer and charging. USB-C is the current reversible connector; the speeds (5 or 10 Gbit/s) indicate transfer speed.
- HDMI (High-Definition Multimedia Interface) - Video output to a screen or recorder. The full-size type A is sturdier than the micro HDMI (type D).
- Ethernet - Wired network port, to quickly transfer images to a computer or a server (FTP, File Transfer Protocol).
- Wi-Fi, Bluetooth, NFC (Near Field Communication) - Wireless links: Wi-Fi for transfers, Bluetooth for the link with a phone, NFC for pairing with a simple touch.
- Microphone and headphone (3.5 mm jacks) - Audio sockets to plug in an external microphone and a monitoring headphone.
Sturdiness and battery life
- Weather sealing - Seals that protect the camera body from dust and moisture (Sony speaks of dust and moisture resistance). It does not make it waterproof.
- Magnesium-alloy chassis - A light and very rigid structure, which gives the camera body its sturdiness.
- Battery life (CIPA) - The number of shots the battery allows with the viewfinder or with the screen. The measurement follows the standard of the CIPA (Camera & Imaging Products Association), which sets the test conditions.
- Weight and dimensions - Weight in grams, and width × height × depth in millimetres.