Buying Guides

Broadcast Cameras/ Camcorders - A Brief History

The progress of recent professional video technology has come on leaps and bounds since the late 70's, when the celebrated U-Matic and Betacam formats were transformed into portable devices allowing ENG recordings and instant playback evaluation of the shot footage. The CCD camera did not exist until the mid 80's and cameras typically used Saticon and Newvicon tubes, which suffered from alignment issues and lag, and they had to be replaced when they eventually went "soft". On the consumer front, VHS and Betamax were competing for market share. As editing or duplicating analogue video was a "lossey" process, the highest quality formats provided the best chance of maintaining and delivering acceptable images.

In-Accurate Control Track Editing

Editing with U-Matic and Betacam was accurate due to the ability to lay a timecode on the tape, but this was not the case for VHS and Betamax as they had no space for a timecode track; editing was CTL (Control Track) based with plus or minus 2 frames accuracy (which became less accurate every time you previewed the edit).

The mid 80's saw eventually Betamax lose the consumer battle with VHS. The VHS format was improved by the higher quality S-VHS format and 8mm, and most notably by the Hi-8 format which also competed for market share.

During this period, the medium which categorised whether a format was broadcast or professional quality was obvious. The vast majority of industrial and professional broadcasters agreed that the Betacam format was the medium of choice. Although the manufacturers now produced VHS and S-VHS industrial editing equipment, the loss process always determined that the format would remain suitable for non-broadcast applications, and the format was generally only used as an offline tool. By the late 80's you could edit the VHS format accurately with VITC (Vertical Interval Time Code) editing controllers and produce an EDL (Edit Decision List) on a floppy disc for the online edit, which was generally Betacam based.

The Digital Era Dawns

The late 80's and early 90's saw the first computer based "offline" systems arrive. The benefit was the ability of the computer to ingest low resolution VHS comparable quality video and allow digital multi pass lossless and accurate editing in a non-linear fashion, and produce an EDL for the online edit. As the technology improved, the computer was capable of ingesting higher quality footage, which matched the quality of the Betacam SP Standard and computerised offline and online systems began to dominate the editing process, due to their lower cost and flexibility of the non-linear process when compared to conventional multi-deck analogue editing.

Digital Tape Format

The mid 90's saw the manufacturers produce digital tape based formats with Digital Betacam, D9 and DVCPRO competing for the broadcast market and DVCAM and DV the corporate arena. The new digital tape formats momentarily slowed the advance of the computer, as the computer ingested only analogue footage at that time. But it wasn't long before the whole process was in the digital domain.

The range of digital recording formats now extends to DV, DVCAM, DigiBeta q,DVCPRO, HDV, HDCAM, P2 and XDCAM - to name a few - with both tape based and solid-state tapeless solutions available. The lower cost of some of these formats and more cost effective editing solutions have enabled millions of amateur videographers to achieve their creative ambitions, making them capable of producing "broadcastable" material. The historical gap between the professional and amateur markets has changed and continues to advance at an unparalleled pace.

When you first open up a specialist magazine or start to browse the internet for camcorders, the sheer range of products can be, well, more than bewildering.

There is a HUGE variety of camcorders from which to select - ranging from entry level camcorders designed for the amateur enthusiast, up to the high end camcorders used by professional broadcasters and film-makers. It can be a little intimidating, trying to choose from amongst them. Ask yourself the following questions:

We at Proactive have compiled a few points you may wish to consider when choosing your new camcorder.

Firewire-Input/Output

If you are planning on both shooting and editing with the camcorder, the Firewire - or I-link (IEE1394) - connection on most camcorders can directly interface to your computer's Firewire port, enabling bi-directional recording between the camcorder equipped with both an input and output Firewire board. This is very useful for quickly transferring your recordings straight to disk and vice-versa.

3-CCD/Single CCD

A 3 CCD camera or camcorder has dedicated CCD's for the primary colours RGB - red, green and blue. Compared to a Single CCD camera or camcorder, 3 CCD's provide more accurately defined images.

Optical Ability

Professional camcorders and cameras generally available have either fixed lenses or have interchangeable lenses. Consideration should be taken dependent upon your specific application when choosing a suitable model. Will you require a fixed or interchangeable lens? A wide lens or adapter? A macro lens? And so on.

Zoom range

The majority of camcorders with fixed lenses are usually supplied with 10x, 12x, 14x or 20x zoom lenses. This is an optical zoom - do not get misled by digital zoom, as this only magnifies a portion of the image thus reducing quality, so always refer to optical zoom if you can.

Audio functionality

Audio is as important as video and the vast majority of Professional cameras and camcorders have Professional balanced XLR mic connections that enable manual audio level adjustment and also greater compatibility with Professional microphone systems.

Look at the type of external microphone plug the camcorder has. The standard consumer version is called a mini-jack; the professional connector is the XLR input which also can provide 48V of phantom power (a method of powering condenser microphones) enabling the camcorder to power the phantom powered microphone.

Manual Focus

Always make sure that you have the option to control the lens focus manually. Whilst a lot of auto-focus lenses cope very well in certain circumstances, a manually controlled lens will always be the preferred choice of the professional, as they enable you to fix focus without the worry of the "hunting" that can occur with auto-focus lenses.

View Finder

If at all possible, always go for a black & white viewfinder, as they have the big advantage that they carry around three times as much pixel information than their colour counterparts, and this in turn means that you are a lot safer in crucial focus situations. A second advantage is that they also have a wider contrast range than the current colour LCD screens. If you are wearing spectacles or contact lenses, check that you can adjust the viewfinder's diopter for your eyesight.

Size

A camcorder's size generally prefigures the fact that the larger the camcorder the steadier your shot, since a shoulder mounted digital camcorder is less shaky than a hand-held palmcorder variant due to arm fatigue experienced with prolonged use. Your shooting application and style should determine the type of camcorder that you require. On Shoulder camcorders have the benefit of allowing more accessories to be attached such as wireless Microphone receivers and onboard lights for example.

LCD screen

This makes framing much easier for the higher and lower angle shots. The majority of modern camcorders have an LCD screen. Also compare the screen sizes, most have 2.5 inch, others maybe 3.5 inches, so it's important to chose the one with which you are most comfortable.

Handling

Try out as many camcorders as you can, see which button arrangement feels most natural to you. Make sure that vital functions (such as manual focus, aperture, white balance and so on) can be changed quickly and easily.

Balance

Front heavy camcorders can cause arm or shoulder fatigue when operated for long periods. Even the smallest palmcorder can become very heavy in long duration hand held situations. Accessories are available to help in these situations and can be found in our camcorder supports section.

Battery life

As a rule with batteries it's always the longer they last, the better. Smaller camcorders are usually supplied with low capacity batteries and upgrading to a larger capacity battery should be considered a priority when initially purchasing a camcorder. The latest high capacity Lithium-Ion batteries are extremely powerful and can provide enough power for up to 8 hours depending upon the camcorder model.

Format

There is a wide choice of different recording formats and standards available. From entry level DV tape to tapeless file based high definition. The choice of format will depend upon both your application and budget.

All of the listed digital format camcorder models have value and performance differences and benefits. We do encourage you to call us should you be in any doubt as to which format will suit your particular requirement. We are fully authorised dealers for all the major manufacturers and have experienced and knowledgeable staff that will offer free and unbiased advice. Demonstrations are also available in our fully equipped showroom by prior appointment.

When building your start-up broadcast kit we understand that you'll need to complement the camcorder with the required or sometimes optional accessories. Here's a referential guide to those accessories.

1. Camera Power Supplies

Batteries are always number the one priority. Without batteries we can't use the camera on location. Your running time requirement should be considered when purchasing as manufacturers will often only include a low capacity battery as part of the supplied accessories with a new camcorder. Consider going for a larger capacity battery, to allow shooting to carry on throughout the day.

Some camcorders only charge the battery "in-camera", whilst others have a separate charger that can only charge a battery or power the camcorder. You may wish to consider a charger that can power the camcorder and charge a battery simultaneously, or maybe a multi-battery charger or in-car charger.

Larger on-shoulder camcorders which have V-lock or gold mounts will not usually be supplied with any batteries at all, due to the higher cost. Consideration should be given to both the running time that you will require and also whether you will want to power a light from the same battery, as most professional mount plates will provide a power output in addition to powering the camcorder.

2. Protection for Your Camcorder

Protecting your investment from the elements is important and you have a wide variety of options available:

Soft Carry Case

Ideal for carrying camcorder with accessories from location to location. Be sure to choose a carry case which can accommodate all the items of kit that you would normally use; such as extra batteries, charger, wide angle adapters and any other accessories you need to bring. Soft carry cases are available as backpacks as well as conventional hand carry cases.

Hard Carry Cases

Most commonly used when travelling overseas as protection in the hold, a hard case will protect your equipment from heavy handling and is the best design if your kit is constantly being shipped. Available in a variety of materials, a hard case can be either heavy duty plastic with an insert that you cut to fit or a bespoke flight case designed to accommodate all your required items. Hard cases can be supplied with wheels for ease of use and with locks for extra security.

Operational Cases

These designs are used with the equipment in situ. Camcorder operational cases are designed for the larger on-shoulder camcorders with access windows provided for all relevant control panels. In addition, an operational case can have an in-built rain protection cover for extra security.

Hard flight cases can also be designed for monitors and VTR's which have removable front and rear panels, allowing them to be used whilst still in the case.

3. Microphones

Wired Microphones

Standard on-camera microphones which connect to the XLR mic input - are generally basic and omnidirectional. They can be changed for higher quality unidirectional microphones. Some microphones can have replaceable front capsules allowing a variety of specific pick up patterns to be used for more flexibility.

A wired microphone can be hand held with a pistol grip or can be mounted on a boom pole. Where more than two microphones are to be used, a field audio mixer will be necessary.

Wireless Microphones

A wireless microphone system comprises a receiver (RX) and a transmitter (TX), and either a hand-held or tie-clip style microphone. They allow the camera operator and the subject freedom of movement and greater distance without cable complications and restrictions.

Headphones

To be able to monitor your incoming audio, a good pair of headphones will be required. Normally they are closed ear styled to keep out external noise and allow precise adjustment and monitoring of your incoming audio levels.

4. Finding Stable Camera Tripods

Tripods provide a stable platform for smoother and steadier shooting. Unlike photographic tripods which are fixed in position, video tripods are designed for movement of both the pan and tilt and will have a fluid head. The fluid head will have a variable or stepped adjustment of the fluid setting. All professional video fluid head tripods will also have an adjustable bowl mount, allowing the head to be independently levelled together with a level bubble for accuracy.

The vast majority of general use tripods are supplied with single or dual stage legs and will have a single pan bar, ground spreader and soft carry case. Additionally, mid-level spreaders, pan bars and dollys are available.

5. Zoom & Focus Demands

For tripod or jib mounted cameras a zoom/focus controller is used to control the speed of zoom and allow the operator to control focus remotely from behind the camcorder rather than leaning over the camcorder for long periods. Audio can also be picked up by the camcorder's on-board microphone whilst operating the controls, but this can be eliminated when using a pan bar mounted controller. Professional lenses generally have separate connectors for both zoom and focus whilst the smaller camcorders with fixed lenses have remote or LANC interface connectors.

6. Camera Light Filters & Lighting

Filters can make a huge difference in a number of situations whether you are indoors, outdoors, in wide open landscapes, in midday sun or sitting in the shade, the right filter will aim to deliver a great image. It doesn't matter whether you're shooting videos or photos, in black and white or colour, filters offer a variety of special and spectacular effects to give you more enjoyment every time you use your camera or camcorder. At Proactive we can supply a massive range of filters either for matte boxes or direct thread fitting.

Whether you require an on camera light or portable lighting kit Proactive are on hand to offer advice depending upon your application. We supply lighting from all the major manufacturers and can offer location lighting for any situation.

For both of these areas, there's a vast array of options and it's difficult to list every single type of filter or lighting setup. Please feel free to contact us and explain what you need and we'll provide expert advice on your best options.

7. Wide Angle Lens Systems

A wide angle is an essential purchase. You will at some stage require a wider shot that cannot be taken with your existing lens. Wide angle lenses are available as adapters that fit onto the front of your existing lens or as lenses that replace your standard lens. Wide angle adapters are available as zoom through or non-zoom through. We have a wide variety of options that are available in all filter and CCD sizes.

Camera Protection

Having made the decision on what equipment to purchase, careful consideration should be taken about protecting your investment - be it from the rain, cold, filming under water or transporting your equipment, we have a wide range of products here at ProActive that will help to keep your equipment safe.

Camera Bags & Rain Cover

A good purpose-built bag is essential for storing and transporting your camera or camcorder to keep it protected from the elements. When choosing the bag, you should consider the size and shape of your camera, the accessories that you would want to carry and the level of protection that you want from any bumps or knocks. We sell an extensive range of both hard and soft cases to cover all needs, including Kata, Lowepro, Peli-Cases, Petrol, Porta-Brace and Sony to name but a few.

When shooting outdoors you should always be prepared for rain. Whether you are shooting a live event or up against a deadline that won't allow you to take a break, a good rain cover is essential to protect your camera while continuing your shoot. Portabrace manufacture operational on-shoulder camcorder cases that protect the camcorder from day to day scratches and dust and in addition have an in-built rain protector should the weather turn during the shoot.

Protective Filter & Camera Glove

The lens forms an integral part of any camera set up and it is therefore very important to keep it protected. A clear filter creates a protective layer on the front of your lens and will save you valuable time and money if it protects the lens from being chipped or scratched.

A protective camera glove can help keep your equipment in the best of condition by protecting it from marks and scratches. A camera glove such as the popular Kata DVG-52 for the Sony HVR-Z1E can also protect your camera from dirt and dust.

Underwater Housing & Flight Cases

Whether you are looking to go to depths of 5m or 50m, Proactive can help you find a solution that will protect your camera whilst underwater. With a vast range of bespoke underwater housings just let us know your camera model and the depths you wish to go to and we can recommend the right housing for you.

When travelling abroad your equipment will not always fit within the flight regulations for taking luggage on board. Feel at ease when putting your camera in the hold by investing in a durable and protective flight case that will safeguard your equipment. The protective cases come in a range of sizes to meet all your requirements, they can be operational where monitors or VTR's can be operated in situ and can have wheels should your equipment be too heavy to carry.

When applied correctly, a filter can become an integral part of the imaging process. Filters use light to enhance and contrast colours to create a specific mood to the image you are shooting. There are a broad range of filters that can be applied - from colour grads, effects and corrections, to neutral density and black and white filtration.

Colour Effect Filters

Colour filters allow you to provide exactly the desired level of colour effect, and are primarily used to add colour to part of a scene where colour may be weak or absent. They enhance reality and can be used to affect elements such as skin tones, sky and foliage. For a softer shade, graduated colour filters are part-clear and part-colour and either transition with a soft edge for gentle merges, or a hard edge for an abrupt change. These are used in uneven lighting situations to balance exposure. Alternatively, day-for-night filters are the perfect way to create a night time or dusking feel when shooting during the day.

Neutral Density Filters

The primary purpose of using neutral density filters is to regulate the amount of light that can pass through the lens. All neutral density filters are grey in colour, and the deeper the colour the more effective the light reduction, whereas graduated neutral density filters brings an overly-bright part of the screen into the dynamic range of film. It is made up of a half-neutral and half-clear density and transitions with either a soft or hard edge. A good example of where to use a graduated neutral density would be where you need to darken a bright sky to allow both the sky and subject to be properly exposed.

Outdoor & Indoor Filters

For use when the sun is too bright and the shadows too dark and it is difficult to get good detail in both at the same time, low contrast filters reduce contrast by allowing more shadow detail visibility, ideal for those who shoot video and desire a film look.

To deal with refracting light, polarisers are ideal when photographing into water or through glass as they are used to eliminate surface reflections, glare or hotspots from any external light sources. They also darken blue skies and increase colour saturation.

Supermist filters are the ultimate tool for softening images to create a mood indoors or outdoors, in broad scenic or portraits. They moderately lighten shadow areas without detracting from the overall image, which allows you to tone down any excessive sharpness.

UV, Skylight and Haze Models

Because CCD's are vulnerable to Ultra Violet rays, if UV light is recorded on the CCD, it is possible that your image will have a blue taint and the colour casts may not be acceptable. These filters can also eliminate a lack of sharpness created by UV radiation and reduces distant haze. UV filters are clear, whereas skylight filters come in a pink shade, which produces a warm glow.

Many camera operators will tell you that a camera is only as good as the glass you put on the front of it. To get the very best images, good optics are a vital element of the camcorder's true performance.

In the professional video industry there are both fixed and interchangeable camera lenses. A standard fixed lens will allow you to add a wide angle or telephoto adapter. Interchangeable lenses allow much more flexibility with higher optical quality, macro facility, larger optical zoom and more precise control of zoom and focus.

Standard Zoom Camera Lenses

We look at a standard camcorder lens as an optic that replicates a perspective very closely to the human eye. For the most part, a standard or normal camera lens will suffice for general shooting situations. We often look at and measure a lens on the amount of zoom it contains, ranging in most cases from a standard 12x zoom up to 20x zoom. With interchangeable lenses you have many mount options, dependant on the manufacturer. There are three main mounts measuring 1/3", 1/2" and 2/3". All lenses differ but generally with a lens you can have two options - a standard professional grade zoom lens or a broadcast-quality zoom lens with an inbuilt x2 extender that doubles the zoom length.

Wide-Angle Camera Lenses

A wide-angle camera lens gives you a wider angle of view, offering a larger perspective enabling a better depth of field. They're best for covering large subject areas. We recommend you look for a wide-angle lens if you want to take footage of outdoor landscapes and outdoor scenes, or for tight indoor shots where space is limiting the coverage that your normal lens can provide. You will at some stage require a wide angle lens or adapter to enable you to get the shot that your current lens cannot.

Wide angle adapters attach to the front thread of the camcorder and are available in two forms, zoom through and non-zoom through. A zoom through version allows the camcorders manual or auto focus to function throughout the entire focal length of the lens while a non-zoom through will allow either no zooming or limited zooming before it loses focus. On professional interchangeable lenses a wide angle adapter is normally focussed with the macro setting and therefore has no zoom through capability. A wide angle lens, rather than an adapter, is a lens that has a wider than standard capability and has a servo zoom function. They are generally more expensive than standard lenses and sometimes replace the existing lens when required. The majority of broadcast camcorder operators have both normal and wide angle lenses available. Most camcorder packages from the manufacturers are supplied with a standard grade industrial lens option or without a lens allowing you to choose the type of lens that best suits your particular application.

Telephoto & Fisheye Camera Lenses

As opposed to the wide-angle camera lens, the telephoto camera lens is a narrow angle lens. It appears to narrow the image, which is important when you are not able to get close to your subject. Appropriate for long-distance situations, a telephoto camera lens is essential for photographing sporting events, animals in nature, and distant landscape features. A fish-eye camera lens is an extremely wide-angle lens. It creates a distorted image that appears convex and most will provide an image 70% wider than your current lens.

Video Compression is the science of reducing transmitted video data without noticeable loss of quality to the original image recorded. It enables transmission using reduced bandwidth for satellite, terrestrial, modem, DSL and ISDN broadcasts. Compression is also used to store digital video. Compression results from an analysis of the original video data source which decides which data to keep and which can be discarded. Discarded data is information that cannot easily be seen by the human eye.

Common Code Analysis

The analysis gives each event a code depending upon its frequency; common occurring events are coded with few bits and less common events are coded with more bits. This encoding is known as signal analysis, quantization and variable length encoding. Too much compression can result in loss of quality.

Compression Video Technology

There are four methods of compression; Discrete Cosine Transform (DCT), Vector Quantization (VQ), Fractal Compression (FC), and Discrete Wavelet Transform (DWT). Most of the compression methods are known as Lossy Compression - this is where files are permanently reduced by discarding irrelevant information. When the file is uncompressed, the data is not the same as the original file.

Understanding Compression Standards

JPEG (Joint Photographic Experts Group)

DV

Digital video is a lossy compression standard providing a high-resolution format for video cameras and camcorders. It uses discrete cosine transform (DCT) to compress the pixel data. Video captured using this format maybe transferred from the Camera/Camcorder using FireWire (IEEE 1394), which is a serial bus able to transfer data up to 50 MB/sec.

H.261

An ITU standard designed for video conferencing as a means of two-way communication via ISDN lines. Data rates are supported in multiples of 64Kbit/s. The algorithm is based on discrete cosine transform (DCT) which can be produced in hardware or software using intraframe and interframe compression, with resolutions supported by H.261 are CIF and QCIF.

H.263

Based on H.261 and has been enhanced to give improved video quality for modem transmission, resolutions supported are CIF, QCIF, SQCIF, 4CIF and 16CIF.

DivX Compression

DivX is a software application to enable video to be downloaded through a DSL/Modem connection. MPEG-4 is the standard used to compress digital video.

Below you can find detailed information about the different video formats available, as well as the advantages and disadvantages of each. This quick reference guide is designed to help you decide which format is best suited to your new project.

Asking whether you should choose 1080 or 720 is like asking how long is a piece of string.

The choice between shooting in 1080 or 720 is probably going to be fixed for you, by the client. Broadcasters in the UK seem to be universally in favour of 1080; 720 is used only for special purposes.

The 1080-line system as used in Europe has 1920 pixels per line and 1080 lines per frame, at 25 frames per second. However, the frames can be either interlaced to give smooth motion (with lower vertical resolution) or progressive (with full vertical resolution) to give film motion. But the smooth motion required for sport can actually be better delivered using a 720-line camera since it can record at 50 or more frames per second; the problem is, will those pictures be accepted by the client, or will they convert them to 1080-line, thereby losing all the advantage of shooting at 720. 720-line pictures have lower resolution (1280x720) but are always progressive, so deliver smooth motion. In general, best results are always got when the camera and recording system all work on the same scanning structure as the final delivery: shoot 1080 for 1080 delivery, 720 for 720 delivery.

Mimicking Film Footage

One camera, the Panasonic Varicam, shoots only at 720, but can do so at varying speeds (4 to 60fps), so is ideal for wildlife photography. It also has some extremely good settings for mimicking film performance, when the footage is shot at, or replayed at, 25 frames per second. For this reason, it is accepted as a source for 1080 programmes, where the footage is used at 25 frames per second.

Bear in mind that the UK's broadcasting of HD is at 1080-line, so 720 is regarded as second class, but that's not all the story. Most of the recording systems do not capture the full 1920 pixels, 1440 is the norm (except for HDCAM-SR, D5-HD and some of the later solid-state capture systems). Also, the HDTV broadcasting is only 1440 pixels wide (1.5Mpixels/frame), and when interlace is used the vertical resolution drops to about 70% so the effective frame resolution is nearer 1440x780, about 1.12Mpixel. If the 720-line camera capture is full resolution (1280x720) it has 1Mpixel frames, not so different from the broadcast 1080, so a well set-up 720 camera is not much inferior to an interlaced 1080 picture. However, the oft-used DVCPROHD recording for 720 does not capture the full 1280 pixels, only 960, so it records only 0.7Mpixels. Nevertheless, the good film look is enough to convince many users that 720 will do.

Tricks Up Their Sleeves

Even so, it isn't as simple as that, because many of the 1080-line cameras do not have 2Mpixel sensors, and so do not deliver the full resolution that 1080 demands. The camera specifications will always give the correct clues: "2Mpixel sensors" means full 1920x1080, "1Mpixel sensors" means 1280x720 (probably), and "520kpixel sensors" means 960x540 (probably). The manufacturers have some tricks up their sleeves, and so can often deliver resolution greater than the nominal pixel count, but it's always a compromise, involving some aliasing along with the wanted responses.

Contributed by Alan Roberts

When you're choosing a camera sensor, you'll need to consider a couple of things. First, you need to decide between a Charge-Coupled Device sensor (CCD) or a Complementary Metal-Oxide-Semiconductor sensor (CMOS).

CCD sensors are cheaper to manufacture than are CMOS, but that's hardly the issue here.

Lower Noise Levels

In theory, there's no difference in sensor performance between these two technologies, but CMOS has one huge advantage: it can incorporate signal processing that's not possible on a CCD sensor. The best advantage for the camera designer comes from incorporating all the analogue parts of the camera on the same chip, thereby simplifying the camera design. This makes it possible to lower the noise level (video noise, not acoustic) considerably, making the pictures more restful and with a considerably higher exposure range. For the user, the advantage comes from lower cost, and the increased exposure range which allows for the capture of a greater contrast range. The sensitivity should hardly be changed, since the photo-sites are still based on the photon-conversion efficiency of silicon.

The advantages of CMOS come into their own when the camera has a single sensor.

Camera sensors: single or 3?

All electronic cameras need to generate three images, R G and B.

In a 3-sensor camera, the light path from the lens to the sensor incorporates a dichroic block, to separate the R G and B images onto the 3 sensors. The assembly of the block and sensors forms one component in the camera, the sensors being glued in place to guarantee that they don't move around in use. The manufacture of this assembly forms a considerable proportion of the cost of the camera, although all broadcast, professional, and high-end consumer cameras are made this way. The sensors can be CCD or CMOS, although most are CCD. The resolution of the camera is defined, or rather limited, by the pixel dimensions of the sensors, the three sensors are always of the same pixel dimensions as each other, and are ideally not less than the pixel dimensions of the video format. There is a trick that can be played during manufacture, called "precision offset", which can deliver up to about 50% extra resolution in either horizontal or vertical directions (or, exceptionally, in both).

Single-Sensor Cameras

In a single-sensor camera, the sensor is almost always CMOS, so that some processing can be incorporated in the sensor. The generation of the R G and B images must come from the same sensor, so pixels must be covered with coloured filters (usually the Bayer pattern), and that means lower sensitivity by up to a stop. However, the video noise level should be lower because all the analogue processing can be done on-chip.

The major difference between single- and 3-sensor cameras is in the level of spatial aliasing they deliver. A 3-sensor camera can deliver clean resolution at the pixel count of the sensors (more if precision offset is used, but with mild aliasing), while a single-sensor camera is almost certain to produce coloured aliasing, because it is impossible to fit a bi-refringent spatial filter best suited to both the resolution of G and of R and B.

Higher Resolution

Single sensor cameras are cheaper, but unless the pixel count is at least 50% greater (preferably 100% greater) than the resolution of the video system, there will always be spatial aliasing in the pictures.

Any camera attempting to mimic a film camera by using film lenses, must be single sensor, and must have the correct lens-to-image distance of 48mm, but it can make good use of wider apertures than can a 3-sensor camera, which is usually limited to F/1.4 by the dichroic block and has a lens-to-image distance of 48mm.

Contributed by Alan Roberts

There are three primary types of video camera shutter: mechanical, electronic, & rolling.

In a film camera, there must be a mechanical shutter to close off the light path while the film is being advanced to the next frame, the film being held still in the image plane for the duration of the exposure. The shutter is a two-bladed fan, rotating at half the frame rate, such that first one blade closes the light path, then the other. The width of the blades can usually be varied for effect, the open period being measured as an angular rotation, with 360 meaning fully open, thus a normal 50% shutter is 180. Actually, this isn't always true: a rotating prism can be used instead of a shutter, directing incoming light onto the correct frame of the continuously moving film. But that's another story.

Video Camera Shutters

Video cameras generally do not need a mechanical shutter, with the exception of the Frame Transfer CCD. Some Thomson cameras have a mechanical shutter for this reason. In television, the use of a shutter will, with this exception, be an artistic tool. The shutter defines the exposure period; the normal, un-shuttered condition is for the exposure period to be exactly the reciprocal of the field rate in an interlaced camera or frame rate in a progressive camera.

Video cameras achieve shuttering by dumping the exposure. The exposure period normally starts at the beginning of a field or frame, and ends at the end of the field or frame, when the charge is read out to form the video signal. But if, exactly half way through this period, the charge is all read out and then ignored, the charge accumulating for the remaining period has an exposure duration of 50% of the interval, 180, just as in a film camera.

Digital Shutters

Before CCD and CMOS sensors, all video cameras used scanning tubes as the sensors. The scanning spot simply discharged the light-sensitive target layer of the tube, line by line, pixel by pixel. This is effectively a rolling shutter, and in the days when all displays were cathode ray tube based, the camera spot and the display spot were always in synchronism, and all was well since the display effectively also had a rolling shutter. However, as pixel-based sensors (CCD and then CMOS) replaced tubed cameras, an odd effect was noticed: on rapid motion, moving edges sloped. This was due to the mismatch between the fixed shutter in the camera and the rolling shutter in the display. The advent of pixel-based displays (plasma and LCD) has cured that and all is well again, but some cameras are reintroducing the rolling shutter for convenience in the processing, and sloping edges are once again on the menu. There is no cure for this, except for ensuring that both the camera and display use the same kind of refreshing mechanism.

Contributed by Alan Roberts

Cameras come in a range of format sizes. In general, the larger the format, the higher the price of the camera, and the more storage is required for the video signal files in post-production.

Movie film formats are generally large and expressed as the width of the film stock itself, while video formats are expressed in terms of the equivalent outer diameter of a scanning tube on the end of which the light-sensitive target is placed. Widescreen variants of the film formats always fill the widths given, but the height may be reduced, or kept the same if an anamorphic lens is used.

Large Format Lenses

Clearly, the smaller the imager size, the greater are the demands on the lens for that format. For example, to achieve 1920 pixel resolution on 35mm film, the lens must deliver resolution up to (but neither including nor beyond, because of the threat of aliasing) 1920/2/22.05=43.5 cycles per mm (or line-pairs per mm). But, to achieve the same resolution on a 1"/3 video camera, the lens must deliver 1920/2/4.8=200 cycles per mm. Nevertheless, such lenses do exist and can perform well, but this shows that it is generally a poor idea to use a small format camera and fit a large format lens to it, the resolution will probably be poor, although the Depth of Field will be that of the larger format lens provided the lens adaptor forms an image within itself, relayed into the camera to fill its imager. If the lens is merely fitted with a mounting adaptor (no optical parts), then the resolution of the lens at its larger format will be delivered to the smaller video camera imager, and the pictures will be soft.

Zone Plate

Lens assessment is best performed using a Zone Plate test chart, since it shows not only the MTF of the lens and camera, but also identifies any aliasing problems caused by either the lack of a bi-refringent spatial filter in the camera, or the filter not being matched to the performance of the lens.

Contributed by Alan Roberts

Creating the perfect shot composition is only half the battle in any video production. Without a clear soundtrack then the whole thing can quickly crumble, requiring costly retakes and unnecessary editing headaches. It is therefore essential for every shoot to have a quality setup of the best possible sound equipment.

Professional Audio Equipment

The vast majority of professional productions will have teams of experts covering each aspect of the filming, from cinematographers and lighting technicians to location scouts and sound engineers. To ensure the success of the project as a whole, it is vital that each individual department is properly briefed and equipped. After all, nothing can replicate the immediacy and spontaneity of a live situation; so each take, regardless of what type of film you're creating, should be treated as if it's the final one - meaning everything has to be technically perfect.

Capturing Clear, Unmuddied Sound

Sound, along with vision, is one of the fundamental parts of any filming process, whether a strictly amateur or completely professional production. Starting with the basics, you will in most situations require an external microphone, overriding the standard one that will ordinarily come attached with any camcorder. With a microphone you are better able to channel the sounds you want directly to the film, whilst cutting out all of the unnecessary nvironmental background noises.

Tie clip microphones - or to give them their proper name, Lavalier microphones - are perfect for discreet and portable sound recording. Fitting neatly on the clothing of the subject - ordinarily a tie or lapel, hence the name - they pick up audio almost directly from the mouth, negating any superfluous sounds.

Versatile Microphone Options

Using a boom along with a shotgun microphone achieves a similar result; although as this is largely directional, it is essential that the operator of the boom maintains a good distance from the subject with the microphone pointing at the source of the sound. Shotgun microphones can also be handheld or even set up on a stand in front of a static interview or similar scenario. The furry windshield - also know as a 'Softie' - that has become synonymous with boom mics used in the media, is particularly useful for outside broadcasts; preventing wind from effecting the quality of audio and airborne particles damaging the microphone.

Handheld mics are an integral part of many interview scenarios. News, sports and other professional broadcasts utilise these simple microphones as they can be easily passed between interviewer and interviewee and work just as well in a report by a single person.

Wireless Sound Solutions

Greater freedom for the roaming video subject can be achieved through wireless microphones. As their name suggests, these mics can travel anywhere without metres of cable trailing around. The signal is relayed via a transmitter to a secondary receptor, which in turn records the soundtrack through a standard system. Just as you'd tune an FM radio at home, your microphone is channeled through a designated frequency to the base unit. Infrared wireless microphone systems are also available; however these tend to be less popular, purely because they are restricted by the need to maintain an uninterrupted beam between microphone and receiver.

Directional & Omnidirectional Microphones

Aside from the numerous different variations with the style of microphones, they can usually be categorised in one of two ways - directional and omnidirectional. A directional microphone will largely pick up sound from a single source, with very little peripheral noise picked up. These are mostly used in situations where you only want to have the subject's voice or a particular noise. Due to the direct nature of the way in which they pick up sound they are extremely clear, although only when facing directly at the subject.

Conversely, omnidirectional microphones have a far broader range for recording sound. By picking up noises over a wider sphere, the omnidirectional mic is ideally used for more atmospheric recording; capturing everything within a scene rather than simply just what the camera or microphone is pointing at. Obviously this does mean that background sounds can impact and overlap on the main filming subject, which does slightly compromise the quality of the dialogue or other recorded material.

Enhance & Convert Sound

Capturing the sound is one thing, but then of course you have to edit and mix the audio to fully compliment the visual. Mixers are just one of the products that can be incorporated into film production, either in the field or back in the editing suite, to really optimise the recording quality of the audio track. Audio converters are also incredibly useful; transposing signal between digital and analogue, allowing you to keep everything in the same balanced format regardless of how the film and audio are individually captured.

Tailoring your Individual Audio Setup

There are plenty of other peripherals that go into making the perfect audio equipment setup; from extra cabling to good old gaffer tape everything needs to be accounted for. But with the increased availability and affordability of professional audio equipment, the modern technician can easily put together a fantastic audio system that's cheaper and of better quality than ever before.

Finding the right equipment to suit your filming needs and setting it all up appropriately are just two of the problems you'll face, but here at Pro AV we're here to help you. Our useful buyer's guides will help distinguish what's right for your production and give you an idea of just what you'll need to get the very best sound for your film. So if you're a little unsure and don't want to waste your time and money getting unnecessary apparatus, be sure to have a look through our Audio Equipment section.