The Truth Behind Tv Cameras: Do They Have Filters?

Television cameras use filters to enhance the viewing experience for audiences. These filters can be used to improve the lighting, colour, and contrast of a scene, as well as to create special effects. The use of filters can be dated back to the early days of film, where techniques such as coloured filters were used to block out certain colours, creating a reveal when the filters were removed. Today, filters are used to create a certain mood or genre, with comedies appearing sharper and bluer, and dramas appearing more diffused and warmer. In addition, filters can be used to smooth skin, with some YouTubers and vloggers using cameras with built-in skin-smoothing filters.

Polarizing filters can reduce glare and reflections, deepen blue skies and intensify colours

Polarizing filters are an essential tool for photographers and videographers, offering a range of benefits that enhance the final image. These filters can be attached to the camera lens and are particularly useful for outdoor photography and filming. One of their key advantages is the ability to reduce glare and reflections from surfaces such as water or glass. This is achieved by cutting out a single wave of direct reflected light, allowing the capture of true colours without the interference of unwanted reflections. For example, a polarizing filter can remove reflections from a window, enabling a clear shot of what's behind the glass.

Additionally, polarizing filters can deepen the blues in the sky and intensify colours, making them darker and richer. This effect is especially noticeable in landscapes with blue skies, where the deeper blues make clouds stand out and give them a more dramatic appearance. The filters achieve this by cutting out polarized light and allowing the camera to absorb more of the sun's rays, thereby increasing contrast and saturation.

The most common type of polarizing filter is the Circular Polarizer (CPL), which is designed for use with autofocus cameras. It consists of two filters that can be rotated to the precise angle needed to capture the desired effect. When using a CPL, it's important to remember that the direction of the light should be at a right angle to the source for the best results. This means that the sun should be positioned at a 90-degree angle to your shooting direction.

While polarizing filters offer significant advantages, they also have some limitations. They work best in bright lighting conditions and are not ideal for low-light or night-time shooting. Additionally, they may not be effective when shooting with the sun directly behind you. It's also worth noting that polarizing filters reduce the amount of light entering the camera lens, so adjustments may be needed to compensate for this.

Contrast control filters reduce the brightness range

Television cameras and viewing conditions can limit the brightness range of a scene. The brightest element in a scene cannot be more than 30 times brighter than the darkest element, with any hope of seeing the detail in each. "Real-world scenes" often contain elements that exceed this brightness range. While lighting can be controlled in a studio, it becomes more challenging outside.

Contrast control filters are used to reduce the brightness range. There are three types of these filters: low contrast, soft contrast, and the Tiffen Ultra Contrast. These filters are used to ensure that the brightest element in a scene is not significantly brighter than the darkest element, thus preserving the detail in each.

The Tiffen Ultra Contrast filter, for example, uses the surrounding ambient light, not just the light in the image area, to evenly lighten shadows throughout. This allows for contrast control without affecting the sharpness or highlight flare of the image.

In addition to contrast control filters, there are other types of filters that can be used to enhance images, such as polarizing filters, which can reduce reflections and glare, deepen the color of blue skies, and saturate colors. Graduated neutral density filters are also useful for controlling the brightness of sunlit areas or bright skies, allowing for a more balanced exposure.

Colour conversion filters correct the difference in colour temperature between incandescent light and sunlight

Colour conversion filters are used to correct the difference in colour temperature between incandescent light and sunlight. This difference in colour temperature is about 2,000K. While professional cameras can electronically perform minor colour corrections, coloured filters are best for major shifts, such as the difference between indoor and outdoor lighting.

There are two series of filters that have been widely used in motion picture production: the Wratten #80 series and the Wratten #84 series. The Wratten #80 series are blue filters that convert incandescent light to the colour temperature of sunlight. The Wratten #84 series are amber filters that convert daylight to the colour temperature of tungsten light.

Videographers use these filters to make the necessary initial adjustment, and then fine-tune the image electronically. This is because the impact of certain camera filters cannot be recreated in post-production. Polarizing filters, for example, can increase detail and contrast in the captured image, improving the detail of the sky and clouds, and reducing glare off glass surfaces.

The kelvin (K) scale is a unit of measurement for temperature and relates to the physical temperature of black body radiators. As black body radiators, such as the sun, heat up, they emit light. A kelvin value can be calculated from the physical temperature of black body radiators, and it is possible to observe that lower-temperature black body radiators emit an orange colour light, and hotter sources emit bluer light. A colour temperature below 4000K will generally appear redder or orange, while a colour temperature above 7500K will start to appear more blue.

Diffusion filters create a dreamy, soft-focus effect

Diffusion filters are used to create a dreamy, soft-focus effect in film and photography. They are optical filters that are placed over the camera lens to achieve a specific visual effect. Diffusion filters work by diffusing light, softening the image, and creating a hazy or dreamy atmosphere. This effect is flattering for complexions and was often used in old Hollywood films to achieve a glamorous look.

Diffusion filters are available in different strengths and sizes, and can be purchased from various brands such as Lee, Cokin, Hoya, Tiffen, K&F, and Moment. These filters can be used with film cameras, modern mirrorless digital cameras, DSLRs, and even mobile phones. When choosing a diffusion filter, it is important to select the correct size for your lens to prevent vignetting.

Diffusion filters are particularly useful for portrait photography, as they can soften wrinkles, reduce blemishes, and smoothen skin tones. They are also commonly used in cinematography to achieve a more natural look and enhance the overall mood of the image.

In addition to diffusion filters, there are other methods to achieve a soft-focus effect. These include using Vaseline or a stocking over the lens, or purchasing a specialist soft-focus lens. However, diffusion filters provide a consistent and precise result, making them a popular choice for photographers and cinematographers.

Graduated lens filters are used when shooting a bright sky

Graduated neutral-density (ND) filters are different from regular ND filters, which darken the whole image evenly. Graduated ND filters have a gradient that goes from dark to clear, allowing photographers to darken just one part of the photo—usually the sky—while keeping the rest of the scene well-exposed. They come in various strengths, typically measured in stops (e.g. 1-stop, 2-stop, 3-stop), indicating how much light they block.

Graduated ND filters are available in different shapes—circular and rectangular (or square). However, professional photographers tend to use rectangular ND grad filters with a filter holder, as these offer more flexibility in terms of positioning the gradient transition. Circular filters, on the other hand, cannot be controlled as precisely.

There are different types of graduated ND filters, including soft, hard, and reverse. Soft graduated ND filters have a gradual transition from dark to clear, making the change in density less noticeable. They are best used for scenes with uneven horizons, like forests, mountains, or cityscapes. Hard graduated ND filters, on the other hand, have an abrupt transition between the dark and clear areas, offering precise control over the exposure balance. They are ideal for scenes with a clear, defined horizon, such as seascapes or flat landscapes. Reverse graduated ND filters are a specialised type used by landscape photographers when shooting against the sun while it is setting close to the horizon. These filters have their darkest point in the centre and gradually become lighter towards the edge, helping to manage the intense light at the horizon without darkening the upper sky too much.

When using a graduated ND filter, it is important to choose the right filter for the scene, identify the dynamic range by taking meter readings of the foreground and sky, and attach the filter using a holder or by screwing it onto the front of the lens. The filter should be positioned so that the gradient aligns with the horizon or covers the brightest areas without darkening the foreground too much.

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