The photography glossary for camera buyers.

APS-C

APS-C is the most common sensor size for mid-range mirrorless cameras. It is smaller than full-frame (which makes lenses cheaper and lighter) but much larger than the sensors in smartphones or compact cameras (which makes image quality much better). The 1.5× or 1.6× crop factor means a 50mm lens behaves like a 75mm or 80mm lens — useful for wildlife and sports, less ideal for ultra-wide landscape work.

Read more: crop sensor explained

Full-frame

Full-frame is the modern reference standard for professional and enthusiast cameras. The sensor area is roughly 2.25× larger than APS-C, which means better dynamic range, better high-ISO performance, and shallower depth-of-field at the same aperture. The trade-offs: bodies are heavier, lenses are larger and more expensive, and the cost of an equivalent kit roughly doubles compared to APS-C.

Read more: crop sensor explained · mirrorless vs dslr 2025

Micro Four Thirds

Micro Four Thirds is the smallest "serious" interchangeable-lens format. Its 2× crop factor is a double-edged sword — a 300mm lens behaves like a 600mm lens (huge for wildlife), but you cannot get the same shallow depth-of-field as APS-C or full-frame. The OM System OM-5 is the standout body in this format; the lenses are very compact, making it ideal for travel and adventure.

Crop factor

A 50mm lens on a 1.5× crop body behaves like a 75mm lens on full-frame — narrower field of view, more "zoomed in" look. This matters when comparing lenses across formats: a 35mm prime on full-frame is a similar field of view to a 24mm prime on APS-C. Crop factor does not affect image quality directly, but it does affect depth of field and what focal lengths are useful for what subjects.

Read more: crop sensor explained

Megapixel (MP)

A 24-megapixel camera produces an image about 6000×4000 pixels — enough for a print up to 50cm wide at high quality. Cameras over 40 megapixels are useful for landscape photographers who crop heavily or print very large; for web, social media, and YouTube delivery, 24 megapixels is more than enough. High megapixel counts mean larger file sizes, slower processing, and more demands on lens sharpness.

Aperture

Aperture is one of the three controls of exposure (the others being shutter speed and ISO). It also controls depth of field — how much of the image is in sharp focus. A 50mm f/1.4 lens at f/1.4 produces a very shallow depth of field (one eye in focus, the other slightly soft); the same lens at f/8 has much more in focus. Fast lenses (those with wide maximum apertures like f/1.4 or f/1.8) are valuable for portrait, low-light, and creative work.

F-stop

F-stops are a logarithmic scale: f/1.4 lets in twice as much light as f/2, which lets in twice as much as f/2.8, and so on. The full f-stop sequence is f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. Photographers often shorthand "wide open" to mean the widest aperture available on a lens, and "stopped down" to mean a narrower aperture for greater depth of field.

Shutter speed

Shutter speed is the second of the three exposure controls. For sports and action you need 1/500s or faster to freeze movement; for handheld general photography 1/60s to 1/250s is fine; for night or long-exposure work you might use 1s, 30s, or longer (on a tripod). Camera shake usually requires shutter speeds at least as fast as 1/(focal length) — so a 200mm lens benefits from 1/200s or faster, unless you have image stabilisation.

ISO

ISO is the third exposure control. Modern full-frame sensors produce usable images up to ISO 12800 or higher; APS-C sensors are typically usable to ISO 6400; Micro Four Thirds sensors are best below ISO 3200. As ISO increases, image noise increases, dynamic range decreases, and colour accuracy can shift. The general approach: use the lowest ISO that gives you a fast enough shutter speed.

Focal length

Focal length determines field of view and how subjects look in relation to their background. Wide lenses (16-35mm) exaggerate distance and make backgrounds look further away; long lenses (200mm+) compress distance and make backgrounds appear closer. The classic focal lengths and their uses: 24mm (landscape), 35mm (street and environmental portrait), 50mm (everyday), 85mm (portrait), 135mm (tight portrait), 200mm (sports), 400mm+ (wildlife and birds).

Prime lens

Prime lenses are the photographer’s discipline lens. A 50mm f/1.8 is the classic example — cheap, sharp, fast (f/1.8 lets in lots of light), and forces you to think about composition. The trade-off is convenience: you cannot zoom in or out. Most professional photographers carry two or three primes (often 35mm, 50mm, and 85mm) instead of one zoom for the best image quality.

Read more: buying vintage adapted lenses

Zoom lens

Zoom lenses are the working photographer’s convenience lens. A 24-70mm f/2.8 covers most general photography needs (wide for landscapes, medium for street, slightly tight for portraits). A 70-200mm f/2.8 covers portrait to telephoto. The trade-off against primes is image quality (modern zooms are very good but rarely match the best primes) and aperture (most zooms have variable apertures like f/4 or f/3.5-5.6, while primes are typically f/1.8 or wider).

Bokeh

Bokeh is what photographers mean by the "creamy" or "buttery" look of background blur in portraits and product shots. The quality depends on lens design more than aperture alone — specifically the shape of the aperture blades, the optical formula, and how the lens handles spherical aberrations. Some lenses are famous for their bokeh character (Helios 44-2 for swirly bokeh, Meyer-Görlitz Trioplan for "soap bubble" bokeh) while modern lenses tend toward smoother, more uniform out-of-focus areas.

Read more: buying vintage adapted lenses

Depth of field

Depth of field is controlled by three things: aperture (wider apertures = shallower DoF), focal length (longer lenses = shallower DoF), and distance to subject (closer = shallower DoF). Sensor size also matters — full-frame produces shallower DoF than APS-C at the same aperture and field of view. For portraits, photographers usually want shallow DoF (background blurred); for landscapes, deep DoF (everything sharp).

Macro lens

True macro lenses produce 1:1 (life-size) reproduction at the sensor — meaning a 24mm-tall insect fills 24mm of the sensor. They are typically primes in the 60-105mm range. Pseudo-macro on zoom lenses usually means 1:4 or 1:5 reproduction — close, but not the same. For real macro work, the Canon RF 100mm f/2.8L Macro, Sony FE 90mm f/2.8 Macro, and Sigma 105mm f/2.8 Macro are the standout options across mounts.

Autofocus (AF)

Autofocus performance is the single biggest difference between modern and old cameras. Pre-2020 cameras often hunt for focus and miss subtle subjects; 2023+ cameras (Sony A6700, Canon R7, Fujifilm X-T5, Nikon Z6 III) have AI-driven subject detection that locks on a face, an eye, a bird in flight, or a vehicle and tracks it through frame-to-frame movement. For sports, wildlife, and video, this matters more than any other camera feature.

Eye AF

Eye AF takes the photographer’s biggest worry (was the eye sharp?) and removes it. Modern Eye AF works at any aperture, any focal length, and tracks moving subjects between frames. For portrait work it is now the standard — almost no professional uses manual focus for static portraits anymore. For wildlife and sports, animal-eye AF and bird-eye AF do the same job for non-human subjects.

Subject tracking

Subject tracking is what enables sports photography. The camera identifies "this is a person" or "this is a car" and holds focus on it even as it moves toward or away from the lens. The best subject tracking systems in 2026 (Sony AI Processing Unit, Canon Dual Pixel CMOS AF II, Fujifilm X-Processor 5) work at burst rates of 20-40fps and recover focus instantly if the subject is briefly hidden behind another object.

4K video

4K video is the working standard in 2026. The differences worth checking on a camera: is the 4K full-sensor (no crop) or cropped? Is the recording time limited (some bodies stop at 29:59)? What is the maximum frame rate at 4K (30fps is common, 60fps is better, 120fps is for slow motion)? Most modern bodies handle 4K well; the differentiators are now overheating limits, autofocus during recording, and audio support.

IBIS (In-Body Image Stabilisation)

IBIS works by moving the camera sensor in real time to compensate for hand movement. The best IBIS systems in 2026 (Sony A7 IV, OM System OM-5, Fujifilm X-T5) are rated for 6-7 stops, which means genuinely handholding at 1/4 second is feasible. For video, IBIS smooths out walking shots — though a gimbal still beats IBIS for serious creator content. The catch: IBIS is rarely on entry-level bodies (no IBIS on Canon R8 or R10, for example).

Open-gate recording

Open-gate recording is one of the most useful features for cross-platform content creators. Cameras like the Fujifilm X-S20, X-T5, Sony A7 IV, and Panasonic GH series support it. A 6K open-gate take gives you 4K resolution in 16:9 horizontal, 9:16 vertical, AND 1:1 square — all from the same capture. The result: you film once and deliver three platforms.

Read more: best cameras for content creators · best cameras for youtube

Log video

Log captures the most data possible from a sensor — protecting both highlights and shadows. The trade-off is that the footage looks flat and gray straight from the camera; you need to apply a LUT (look-up table) or manually colour grade it to make it look right. For serious YouTube and film work, log is essential. For most everyday creator content, the camera’s standard or film simulation profile is fine.

Sony E-mount

Sony E-mount was launched in 2010 and is now the most mature mirrorless mount. There are native lenses from Sony, Sigma (excellent and often cheaper than Sony), Tamron (good zooms at affordable prices), Tokina, Samyang, and dozens more. Cheap adapters (€15-30) let you use M42, Canon FD, Minolta MD, Olympus OM, and other vintage lenses with manual focus.

Read more: buying vintage adapted lenses

Canon RF mount

Canon RF mount launched in 2018 and is growing fast. Native RF lenses (RF 24-105mm f/4, RF 70-200mm f/4, RF 100-400mm) are excellent but expensive. The killer feature is the Canon EF-EOS R adapter (€80) which makes every Canon EF and EF-S lens from 1987 onwards work natively on RF bodies — full autofocus, full IS, full electronic aperture control. This essentially gives RF the world’s largest lens ecosystem.

Read more: buying vintage adapted lenses

Nikon Z mount

Nikon Z mount launched in 2018. Native Z lenses are excellent (the Nikkor Z 50mm f/1.8 S and 24-70mm f/2.8 S are among the sharpest lenses ever made), but third-party options are still limited compared to Sony E. The FTZ II adapter (€110) is essential if you have any Nikon F lenses — even older AF lenses autofocus through it.

Fujifilm X-mount

Fujifilm X-mount launched in 2012 and is one of the strongest APS-C ecosystems. The Fujinon XF lenses are uniformly excellent (XF 23mm f/1.4, XF 56mm f/1.2, XF 16-55mm f/2.8 are standouts). Third-party support is growing — Sigma now makes X-mount versions of their best APS-C lenses. The mount’s short flange distance also makes it excellent for adapting vintage glass.

L-mount

L-mount is the L-Mount Alliance (Panasonic, Sigma, Leica) standard, launched in 2018. The unique feature is cross-brand compatibility: any L-mount lens works on any L-mount body. Sigma in particular has produced an impressive lineup of L-mount primes and zooms. The downside is the alliance is smaller than Sony E or Canon RF, so the lens ecosystem is more limited.