Broadcast-safe video and technical effects explained
The broadcast-safe limiter, processing amplifier, gamma, log film converter, interlace flicker and other technical effects in Video by Zaweba, explained.
Not every effect is about looks. Some exist to make a picture technically correct, or to do one precise job that a grading tool would do less directly. Video by Zaweba gathers these in a group: lighting, extract, processing amplifier, colour decision list, broadcast-safe limiter, gamma, log film converter and reduce interlace flicker. Most people won't need all of them, but each one solves a real problem when it turns up.
Broadcast-safe limiter
Television has rules about how bright, how dark and how saturated a picture may be. Pictures outside those limits can cause problems on broadcast equipment and look wrong on some sets. The broadcast-safe limiter holds the picture within safe levels, pulling down highlights and colours that go too far.
If your work is going to a broadcaster, a festival or anyone with technical delivery requirements, put the limiter on as the last step, often on an adjustment layer covering the whole timeline. Check the result with the waveform and vectorscope in View, then Scopes. There is also a broadcast-safe limiter among the export options, if you would rather apply it at the end.
Processing amplifier and gamma
The processing amplifier, often called a proc amp, takes its name from a box in broadcast equipment that traditionally adjusted the basic levels of a signal, such as brightness and colour. As an effect, it can be stacked, masked or applied to a track, which is sometimes handier than the per-clip colour controls.
Gamma adjusts the midtones of the picture without moving the darkest and brightest points. It is useful when footage looks right at the ends but too dark or too light in the middle, which can happen when a file has been converted between systems with different assumptions.
Log film converter and colour decision list
A log film converter turns a flat, log style picture into normal contrast. For camera footage, the per-clip input colour space setting covers Sony, Panasonic, ARRI and Canon log curves, but the effect is useful when footage needs a conversion as a step within a chain of effects, or when it isn't one of those cameras.
A colour decision list, or CDL, is a standard way of describing a basic colour correction with a small set of numbers for slope, offset, power and saturation. Colourists and visual effects teams use CDLs to pass corrections between programs. As an effect, it lets you apply or reproduce one in Video by Zaweba.
Extract and lighting
Extract keeps or removes parts of the picture based on brightness, which helps when building mattes or isolating bright details. Lighting adds the effect of a light shining on the picture, which can relight a flat shot slightly or draw attention to part of the frame.
Reduce interlace flicker
Older video, and some broadcast material, is interlaced: each frame is made of two fields of alternating lines. Fine horizontal detail, such as thin lines in text or patterned clothing, can flicker on interlaced displays. Reduce interlace flicker softens that detail vertically just enough to calm the flicker. It is especially useful on titles and graphics with thin horizontal strokes, if your delivery is interlaced. Video by Zaweba can export interlaced formats with upper or lower field first for several codecs.
Using technical effects sensibly
Put technical corrections in the right order. Conversions such as a log converter or a CDL usually go early, before creative work. Safety limiting goes at the very end, after everything else, so nothing added later can push the picture out of range again.
Don't use the limiter as a grading tool. If a shot needs heavy limiting, its grade is too strong. Correct it properly and let the limiter catch only the odd stray peak.
These effects are rarely glamorous, but they are the kind of thing that makes Video by Zaweba usable for professional delivery as well as home projects.
