Film photography

Film photography has never quite gone away. In fact, it’s enjoying something of a resurgence amongst photographers who miss the imperfections, unpredictability and individual characters of film, chemicals and darkroom processes.


While most cameras now let you compose your shots using an LCD screen on the back, there are lots of times when a regular viewfinder is still preferable. For many people it’s more natural to put your eye to a viewfinder eyepiece than it is to hold the camera at arm’s length. Viewfinders are also more useful in bright light, when glare often makes it hard to see what’s being displayed on an LCD screen.

Viewfinders come in different types. Some older cameras have ‘direct vision’ viewfinders, digital SLRs have optical through-the-lens viewfinders while mirrorless cameras use electronic viewfinders.


Most of us take photographs in whatever light is currently available but pro photographers will often want to take control of the lighting by introducing their own. It may be as simple as a single flash unit or as complex as a multi-light setup fired by remote control.

Photographic lighting comes in many different types and styles, from mains-powered studio flash to battery-powered location lights for stills and video.

Dual Pixel CMOS AF

Dual Pixel CMOS AF is an autofocus technology developed by Canon that aims to deliver the speed and responsiveness of phase detection autofocus using only the camera sensor and not a separate phase detection sensor. This has many advantages for mirrorless cameras and DSLRs being used in live view mode. Effectively, the photosites on Canon’s sensor are split into two, and the two ‘halves’ can be used to measure the distance of the subject by how much the two halves are ‘out of phase’. Other makers have their own on-sensor phase-detection autofocus systems. It erodes one of the few remaining advantages of DSLR cameras over mirrorless models.


This is a key part of the optical viewfinder system of a digital SLR. It’s a five-sided prism inside a housing on top of the camera that reflects the image captured by the lens and formed on the camera’s focusing screen so that it’s the right way up and the right way round for viewing through the camera’s viewfinder eyepiece. Some cheaper DSLRs use a less expensive ‘pentamirror’ design instead. It costs less to make but does have a slight effect on the size and quality of the viewfinder image.

360 video

This is fully immersive video that’s been shot with a 360-degree video camera. The video footage extends in a full circle around the camera position, which is usually stationary but could also be mounted on a skydiver’s helmet, for example. There are two ways of working with and watching 360-degree video. One is to use the video as raw material for creating a regular rectangular video, but with the freedom to pan around through a full 360 degrees during the editing process as you choose your viewpoint or create your own ‘panning’ shots. Another is to distribute the 360 video as-is using a suitable display system so that viewers can explore the scene on their own, choosing which direction they want to look in.

Perspective control lens

Perspective control lenses have special tilt and shift movements for correcting converging lines (shift movement) in architectural images, for example, and adjusting the plane of sharp focus (tilt movements) for objects at an angle to the camera. By applying a vertical shift you can bring the top of a tall building into the frame without tilting the camera (this is what caused the converging vertical effect). By applying a tilt movement to the lens you can change the plane of sharp focus away from the perpendicular towards the plane of your subject – this increases the depth of field available.

See also: Lenses explained

Image circle

All lenses produce a circular image on the camera sensor or film, and this ‘image circle’ must be at least large enough to cover the full film/sensor area. Different lenses designed for different sensor sizes and formats have different-sized image circles. Lenses designed for APS-C format cameras, for example, have a smaller image circle than lenses for full frame cameras. Some specialised perspective control or tilt-shift lenses have larger image circles to allow for lens movements relative to the camera.

See also: Lens explained

Image editor

Any program which can edit, enhance or manipulate digital images is technically an image editor, though usually this term is reserved for more advanced, technical programs like Photoshop rather than simpler everyday photo management tools like Apple Photos or Google Photos.

Group (lenses)

Camera lenses used complex configurations of different optical elements, often cemented or fixed together in ‘groups’. Lens groups may be designed to counteract common optical aberrations and you may have autofocus ‘groups’ and zoom groups. Lens elements and groups often move relative to each other in complex ways as the focus and zoom settings are changed.

See also: Lens explained

STM (Canon)

STM stands for stepper motor lenses, a new type of autofocus motor used by Canon in some of its lenses. Stepper motors offer fast, precise and quiet focus adjustments, so these lenses are well suited both to regular stills photography and to video, where autofocus noise can be picked up very easily by the camera’s internal microphone. Canon’s STM lenses work very effectively with cameras using Canon’s Dual Pixel CMOS AF autofocus system.

See also: Autofocus basics