9 Introduction to In-camera Picture Effects
Early video cameras were sensitive to only a narrow exposure range, leading to a ‘contrasty-video’ look with fuzzy highlights and inky shadows. Modern cameras are now approaching a similar exposure range of film and many provide adjustments to the image and frame rate to further emulate film. These ‘treatments’ can create a film- look; for example, a warm tone and deep blacks. Alternatively, they can be set to capture a wide range of tones with details in the shadows and highlights, providing the best raw and ‘unprocessed’ footage for applying a certain ‘look’ in post-production.
The former suits situations where fast turnaround is required, but once shot with its look, it cannot be undone – and it may be difficult to cut with other material so such settings should not be too extreme. The second method can generate rushes that initially look bland, but once grading is applied (see Post Production – section 4. Picture Grading), detail is retained in wide exposure ranges whilst providing a gentle roll-off in highlights, detail in skies and texture in shadows.
In many cases, the same effects can be achieved on un-treated footage in post production by using digital filters and effects. Videographers must be fully aware of the results of applying these settings before implementing them!
9.1 Black Stretch/Compress
The human eye is well equipped to resolve detail in scenes with a massive range of tonal or light levels. Unfortunately, video cameras are not that intelligent nor sensitive, and will average the overall tonal or gamma range within a scene based on its darkest and lightest points. This can result in a shot which looks fine overall, but will lack detail within the darker areas.
Most commonly seen on professional and broadcast level cameras, Black Stretch/Compress provides an extremely useful adjustment of the darker areas of a shot or scene. It enables the operator to bring out (or reduce) the detail within these dark areas by increasing (or decreasing) the tonal range in the darker parts of the picture only, whilst leaving the brighter parts of the picture unprocessed.
The creative applications of Black Stretch/Compress include being able to film scenes with a greater variety of tonal range, whilst still being able to draw the viewers attention to detail within the darker areas by stretching the black (giving more tonal detail), or by compressing the black areas (reducing tonal detail) to concentrate the viewer to other parts of the picture.
Whilst adjustment to darker parts of the picture can be made at the post production stage, this will generally degrade the overall picture quality. It is therefore preferable to have this adjustment facility available to you at the filming stage.
9.2 Skin Tone or Skin Detail
Known as either Skin Tone or Skin Detail, this setting has an effect on the way the camera records human skin. It is used in situations where there is a need to capture a more complimentary or natural-looking recording of human skin. A common example of this would be to reduce wrinkles or minor blemishes in an actor’s face. However, the camera cannot differentiate between a face and other features within the frame which have a similar tonal or colour range, so caution must be used when introducing this feature.
Essentially, this feature works by processing the colour range commonly found on the human face by suppressing the outlines of tonal changes and giving a smoother progression from one tone to another. In the case of a wrinkle, the tonal qualities will change from the edge of the wrinkle to its centre. Cameras will generally give a choice of settings (commonly referred to as ‘Skin Tone Detail’ settings), which will alter the tonal range from a narrow to a wide range of skin tones. In addition, cameras are also able to set the intensity of the effect (commonly referred to as ‘Skin Tone Level’).
9.3 Gamma & Frame Rate Settings
| Like Skin Tone, Gamma settings will have an effect on the tonal qualities of your picture. However, unlike Skin Tone, these adjustments will change a much wider range of colours and are used to give your pictures an overall tonal quality. In general this is done by altering the overall contrast and chroma settings within the camera, but great care should be taken as, once applied and recorded, these effects are difficult to remove in post production. |
| To emulate the frame rate of film (24fps), some cameras have a simulated progressive filming mode (often referred to as ’25p’). This works in a similar way to a slow shutter speed by discarding one field and doubling the information of the other.
In PAL cameras this is set to 25fps, and combined with film-type gamma settings, a more ‘filmic’ look can be achieved. However, be aware that these effects are virtually impossible to remove in post production! |