Tech talk
Video jargon can be intimidating, so here’s a quick jargon buster
4K UHD vs Cinema 4K: What most people refer to as ‘4K’ is actually UHD, or 3,840 x 2,160 pixels. It has the same 16:9 aspect ratio as Full HD, with twice the horizontal and vertical resolution. Cinema 4K has a resolution of 4,096 x 2,160 pixels, which gives a slightly wider 17:9 aspect ratio.
Bit rate: The term for the the level of compression applied to video footage. Higher compression (a lower bit rate) produces smaller files but lower-quality video, while lower compression (higher bit rate) produces larger files but better-quality video. Different cameras record at different bit rates.
Bit depth: Most cameras capture 8-bit video, which has similar limitations to 8-bit JPEGs and can start to break up and show banding or posterisation effects with heavy editing (or ‘grading’, to use the video term). Some cameras can capture 10-bit video, which offers more scope for editing later.
Colour sampling: Video is recorded as a luminance channel and two chroma channels. Compressing chroma (colour) data is less harmful to the image quality; this compression is quoted as a ratio. Ideally, cameras would record 4:4:4 video but usually compress to 4:2:0 (basic) or 4:2:2 (better).
Frame rate: The traditional frame rate for movies is 24fps; for PAL broadcast TV it’s 25fps; and for NTSC broadcast TV, it’s 30fps. Now that most video is transmitted and viewed digitally, distinctions between PAL and NTSC are less relevant but the frame rate still affects the ‘look’.
Interlaced vs progressive: Interlacing is where two ‘fields’ of odd and even scan lines are stripped together. It saves on processing power and bandwidth, but isn’t as good as ‘progressive’ video, where each frame is captured whole. Interlaced video has an ‘i’ suffix; progressive video has a ‘p’.
Intra-frame vs inter-frame: Intra-frame compression compresses each frame individually and gives the best quality frame by frame. Inter-frame compression only stores the changes between ‘key’ frames. The choice may be expressed as ‘All-I’ (intra-frame) and ‘IPB’ (inter frame) compression.
Log modes: these capture ‘flat’ video with a wider brightness range, which is designed to be edited (or graded) later. All camera makers have their own versions of log modes, such as S-Log (Sony) and C-Log (Canon). Log modes are a selling point for videoorientated cameras.
Oversampling: A processing technique where video is captured at a higher resolution than 4K then ‘downsampled’ to its final 4K resolution. This can produce better-quality video and is sometimes used on cameras where the native sensor resolution is much higher than 4K.