Effects executed live on set — explosions, fire, water, smoke, blood squibs in front of camera. No render time, immediate preview.
More happens on set than the camera later sees — and that's precisely where practical effects come into play. You set up an explosion, ignite it, and the camera captures the real bang, the real shockwave, the real debris. No rendering. No late nights in the editing suite. This is the counter-principle to CGI, although both have long been working hand in hand today. A practical effect thrives on immediacy: the actor reacts to real fire, real water jets, real shaking — and this physical authenticity is embedded in every frame.
The craftsmanship aspect is crucial. You need an effects master who understands explosives, material behavior, timing, and safety. A blood splatter sequence with practical effects — whether a burst head or a shot-through wall — is built on location with hydraulics, gelatin packs, or spray systems. The DoP immediately sees how light and material interact; no textures, no displacement maps. A smoke bomb in the background, strategically placed, gives you volume and movement that CGI smoke rarely achieves authentically — because real smoke obeys physics and air currents, not algorithms. The advantage: zero latency between action and result. Disadvantages: repetitions are expensive, quality depends on external factors (wind, temperature), and safety is non-negotiable.
In practice, we mix both today. An explosion is ignited practically, then the VFX supervisor enhances the impact with digital secondary effects in editing — additional light flares, debris trails, smoke intensification. A shot that destroys a window is filmed practically (with breakaway glass and pyro), but the slowness of the glass shards in slow motion is often duplicated and digitally enhanced. This is called a hybrid approach, and it has become the standard.
For cinematographers, this means establishing fixed positions in good time, because practical effects cannot be repositioned afterward. Communicate with the effects team beforehand about sightlines, light changes, and smoke clouds. Raw energy in the image remains irreplaceable — but post-production polishes, intensifies, and supplements where reality alone becomes too subtle.