Q: What kind of equipment is available for underwater video photography?

A: There are no underwater camcorders; but sealed housings are available for a variety, but by no means all, of the existing models. Ewa-marine flexible video housings can be used to a depth of 10m, and so are suitable for swimmers, snorkellers, and shallow-working divers. For deeper sport and professional diving, pressure resistant (hard) housings are available from numerous manufacturers (see products section, video). Some systems allow the camera to be used with a wide-angle adapter, and this helps to offset the problem of poor underwater visibility by reducing the lens to subject distance. Underwater colour correction filters can be accommodated by most housings, and these help to reduce the blue colour cast when working at moderate depths.

An underwater video light improves results considerably, and is essential in situations in which natural light is insufficient. To qualify as a video light, a light source must provide even illumination (freedom from hot-spots), and should have a reasonably high colour temperature (at least 3200K), which means that ordinary underwater torches are not good enough. Video lights are available from various manufacturers, and are usually powered by heavy Ni-Cd or Lead-acid batteries. Since the power source must be carried by the diver, burn times for tungsten filament lamps are necessarily limited (rarely more than 1 hour, and often considerably less). High efficiency HID or LED lamps use about 20% of the power of an equivalent tungsten lamp and are to be preferred.

For motion picture photography, a video light should preferably be fixed rigidly to the camera housing by means of a lighting support arm. For close-range working, a video lamp may be mounted directly above the housing. In this case, the lamp may be attached to a standard accessory shoe (if provided). For medium-range working, the lamp should be further away from the camera lens, and a longer articulated (jointed) arm is to be preferred. Arms with 1" diameter ball joints can support lights weighing up to about 2-3kg in air. The Ikelite 1.25" ball-joint system can support in excess of 3Kg in air. Other arms, particularly segmented arms, will droop when holding heavy lights in air, but will work acceptably underwater if not excessively loaded.

Q: Which video camera should I buy?

A: The first point to note is that the range of underwater housings available 'off the shelf' is limited, and if you are considering a particular camera, you should make sure that there is a housing for it before you buy it. If this advice is too late, a custom housing is a possibility (Ikelite, Birchley Products, others?). Ewa marine flexible (10m) housings cover the largest range of models, for the simple reason that each product usually fits several camcorders. Hard housing manufacturers, on the other hand, must either provide a mechanical linkage to each control brought out, or electronics to communicate with the remote control port. Consequently, economies of scale dictate that manufacturers stick to making housings for major brand-name camcorders (Sony, JVC, Panasonic, Canon), with Sony as the main target of interest.

UK buyers may note, that there are housing manufacturers in the USA and Australia who have never marked their products in the UK or Europe. Such product may serve your purposes well, but maintenance will be more expensive, and complaints difficult to pursue due to lack of local after-sales service. Suppliers do not refund postage and other expenses incurred in pursuit of warranty claims.

Given the need to edit footage to make it watchable, digital camcorders are to be preferred. The point about digital recording is that there is no generation loss, i.e., once the analogue video signal has been digitised, transferring it from one tape or medium to another does not degrade the picture quality (provided that the transfer carried out in the digital domain (via i.Link) - quality loss will occur if the signal is converted back to analogue and then re-digitised). Most current digital camcorders use the Mini-DV casette format for recording and this is to be preferred for new buyers. If you have an archive of old Video-8 or Hi-8 recordings, you might also consider buying a Digital-8 (D8) camcorder. D8 camcorders make digital recordings on 8mm tape, and most models can also playback analogue recordings and convert them to digital.

Cameras which use 3 CCDs (separate red, green, and blue, rather than a single CCD with a colour stripe filter) give the best image quality.

Q: What will the sound quality be like?

A: The short answer is; awful. Most camcorders use a microphones either built into or mounted directly onto them, and set the recording level by means of an automatic gain control (AGC) system. Sound waves travelling in the water will couple only weakly with the air cavity inside the housing, and so the camcorder will turn up its gain until the background noise dominates. This generally leads to a good recording of the motors in the camcorder, with the muffled sound of the divers breathing in the background. The bottom line is that proper sound recording facilities are not a standard provision. If you want to record whale-song etc., you must use a device called a 'Hydrophone'. These can be fitted to the front of some hard housings, or can be used in conjunction with a separate audio recorder.

Q: Will my video tapes and equipment work with equipment from other countries?
Q: Can I play video tapes from other countries?
Q: Will I be able to show my recordings using the TV in the hotel or dive school?

A: Different countries use different TV standards. You need to know about this if you intend to buy video equipment from another country (even from within the EC), or if you intend to exchange video tapes or signals with foreign equipment. This section gives a short overview of the issues. For a more detailed account, see the world TV standards article.

A national analogue Television standard has three parts: a basic monochrome (black & white) standard, a colour encoding method, and a transmission standard. The monochrome and colour parts make up the Video standard, and the transmission part takes care of details like the sound channel, the modulation polarity, and the television band (VHF/UHF) to be used. Satellite and digital signals are usually transcoded to the national standard in set-top boxes, so the national standard is usually the target of interest from a compatibility point of view.

In general, countries with 60Hz mains supplies use a video standard based on 525 lines, 30 frames/sec. Countries with 50Hz mains supplies tend to use 625 lines, 25 frames/sec. Colour signals are optionally added to these basic standards according to encoding schemes known as NTSC, PAL and SECAM. 525 line countries predominantly use NTSC, although there are parts of the world (i.e., Brazil) where 525 line PAL (PAL-M) is used. 625 line countries are split between PAL and SECAM, with SECAM appearing mainly in areas of French or Russian influence, and PAL almost everywhere else.

TV and Video signal compatibility:
Many modern TV sets (Sony and Others) actually support both 625 line PAL and 525 line NTSC via the SCART, Video or S-Video sockets (check the product literature). Some may also support 625 line SECAM. Due to differences in transmission standards however, multiple standards are only likely to be supported via the antenna (aerial) socket in countries where several different standards are in use. The problem is that TVs are like refrigerators, they have a 10-15 year service life, and you are quite likely to encounter old equipment.

If you feed into a foreign TV set via a SCART, S-Video, or composite (CVBS) video socket, you may find that you can get a monochrome picture even if the line standard is not officially supported. This is because the horizontal scanning frequencies of the 525 and 625 line systems are very similar (15.734 vs 15.625 KHz), and a small tweak on the Vertical Hold control can make up the difference between 25Hz and 30Hz frame rates. Your chances of getting a colour picture are zero however, unless both the line and the colour standards agree. If you feed the wrong line standard to a VTR, and ask it to record, it will probably behave very strangely as it struggles to lock onto signals which are outside its range, but you are unlikely to do any damage. If you want to power your camcorder from the mains while experimenting, don't forget that you will need the right mains adapter for you host country.

If you intend to use direct video input, and the line standard is right but the colour standard is wrong, you may be able to get hold of a colour transcoder. This is a box which takes a video input in one colour standard, and gives an output in another, but does nothing to the basic monochrome signal. If the line standards differ, the only recourse is a TV standards converter, and you're not likely to come across one of those unless you're visiting a TV company or a transcription specialist.

If you need to use an RF modulator ( the thing that goes into the TV aerial socket), the situation is complicated by the details of the transmission standard. Some countries use both UHF and VHF, but some only use one or the other, and your modulator may not have the right type of plug. Once connected and tuned in, you may then find that the modulation polarity is wrong, in which case you will get a negative picture which will only lock with critical tweaking of the Horizontal and Vertical Hold controls. The chances are that you will get at least a monochrome picture however, but you may not get sound.

If you're in a country where you know that the line and colour standards are the same as yours, but you get no sound through your RF modulator, look to see if it the modulator has a sound system switch. For example, modulators supplied to the UK often have a tiny switch marked I-G. This switches between the +6MHz FM system used in the UK and Eire, to the +5.5MHz FM system used in most of Europe, Australia, and many other parts of the world. If this fails, and you still feel that the sound is worth reviewing, you'll have to use headphones or take a direct audio feed from the camcorder to a Hi-Fi amp.

Videocassette compatibility:
The strange situation with analogue video tapes, is that PAL and SECAM are incompatible if you use ordinary VHS or 8mm, but they are compatible if you use SVHS or Hi-8. The reason for this is that the high-band versions of these domestic formats don't have a specification for SECAM at all, and the VTRs designed for SECAM countries transcode to PAL before recording and transcode back to SECAM for playback. Remember that this only works with Hi-8 and SVHS (or SVHS-C) tapes, and that ordinary domestic VTRs cannot play these tapes.

Playback of 525-NTSC tapes on 625-PAL VTRs, and vice versa, usually depends on the use of so-called 'hybrid' video standards. This capability is only provided on professional and high-end domestic VTRs, and if you want it, you must check for it in the product specification. Essentially, the 525-NTSC machine plays back PAL as 625 line NTSC, and the 625-PAL machine plays back NTSC as 525 line PAL. It may therefore take a tweak of the TV's Vertical Hold to get the picture to lock in either case, and the picture geometry may be affected, but the results are usually satisfactory. Newer VTRs, designed to work with multi (video input) standard TVs, may be designed to play back tapes using their native video standards, this is obviously the best way to do it, but no use unless you also have the multi-standard TV.