Q: What mains adapter do I need for a particular country?

A: Countries of the world are divided roughly into those which use a 100-120V 60Hz supply, and those which use 220-240V 50Hz supply, and the mains plugs in use are many and various. Travel adapter plugs, available from hardware stores, cover many of the eventualities, but to be on the safe side, you should take a free socket (the thing that goes on the end of an extension lead), a short length of mains cable, and a some electrical screwdrivers (Philips and flat-blade, or a Swiss Army knife). You can then go into a hardware store almost anywhere in the world and buy a mains plug of the local variety.

Britons travelling to the Maldives or the Indian sub-continent may notice that various listings give the mains plug type as British. Some 13A rectangular-pin plugs are in use, but you will mainly encounter the 5A and 15A round-pin types, which went out of use in Britain in the 1950s. British round-pin plugs are still available in the UK, and you can get them (and multi-way adapters) from junk shops and jumble sales if you don't mind the fact that un-shrouded pins do not conform to UK health and safety regulations. In the Maldives, you will probably have to go to Male to get mains plugs, so its best to take some with you.:

British 5A Plug: MK Electric No. 505 (standard white urea-formaldehyde), RS stock No. 325-179.
British 15A Plug: MK Electric No. 515 (standard white urea-formaldehyde), RS stock No. 325-185.

Unfortunately, chargers and mains adapters which are switchable from 115 to 230V do not qualify for the European CE mark (because there is the chance that you may blow it up by leaving the switch in the wrong position - been there, done that), and so they have (virtually) disappeared from the European market. The alternative is the much more expensive electronic 'switched-mode' charger, which can adjust itself to any of the world's mains supplies.

Q: What happens if I exceed the depth rating?

A: The important thing to understand is that the depth rating is not the depth at which the equipment will self-destruct. Usually, it is simply the depth to which the equipment is tested at the factory, and consequently the depth to which the equipment is warranted as fit for service. It is also a figure set by the test engineers as being of sufficient safety margin to ensure high reliability in normal service. If you exceed the depth rating of a hard housing, it will at some point fail in one of two ways: either by implosion, or by O-ring extrusion. 'Implosion', which may be preceeded by cracking, is the collapse of the housing walls because they are no longer strong enough to withstand the pressure. It is also a distinctly possible, and catastrophic, failure mode of flat glass optical ports. 'O-ring extrusion' is the forcing of the O-ring through the tiny gap which it is intended to block. O-ring extrusion can occur if too soft an O-ring is fitted, or if the O-ring has been degraded by age and chemical attack; but if the equipment is properly maintained, a well designed housing should be able to withstand immersion to at least 1.5 times its rated depth. This does not mean that you should deliberately exceed the rated depth, and you will invalidate the warranty if you do (if it fails, what you have done will be obvious from the damage caused), but it does mean that you should not panic if you accidentally take a 45 metre housing to 50 metres. This information, incidentally, only applies to proper diving housings of robust design. It does not apply to splashproof and 'waterproof' (e.g., 2m) housings, and it does not apply to housings with thin walls, some of which can be seen to bow-in under pressure and can barely meet their published specifications. Exceeding the depth rating by more than a few percent is also a particularly dangerous activity when using flat glass optical ports, because they give no visible warning of impending failure, they just go "bang!".

Q: I'm thinking of going over to digital photography, what does it entail?

A: If you are an established photographer, you will probably have a large collection of images on film. Consequently, you will need to buy a scanner if you want to bring these images into the digital domain. Affordable scanners for negatives and transparencies come in two basic forms: film scanners, and flatbed scanners with a transparency drawer or lid. For images on 35mm or medium format film, a flatbed with a transparency lid will probably have insufficient resolution to be useful for high quality photography, and the best option by far is a dedicated film scanner. When selecting a scanner, the most important part of the specification from the photographers point of view is the bit-depth and maximum density range DMAX (both of which are related). Scanners are available with bit-depths of 24, 30, and 36 or more bits-per-pixel, but if you want to make high-quality scans from photographic originals, 36 bpp or more is your only serious option. 24 bpp is good enough for web publishing, but the image files produced have no latitude for contrast adjustment and so generally do not produce prints of comparable quality to a photograph. 36 bpp scanners, on the other hand (depending on the supplied software to some extent) have sufficient lattitude to allow recovery of previously unusable images, and can even correct for crossed-curves and other development disasters. With regard to the resolution of the scanner, consider only the optical resolution, and ignore interpolated resolution, which is merely a marketing red-herring. Choose an optical resolution such that the number of pixels-per-inch of your largest required print does not fall below about 144. Eg., if a film scanner has a maximum optical resolution of 2700ppi, a whole 36 x 24mm frame from a 35mm film comes out as 3826 x 2551 pixels. When re-scaled to144ppi, this will give a print of 26.6 x 17.7", which is considerably larger than a sheet of A3 paper. Note that although 72ppi is the standard for web publishing, for a print to look good, the linear resolution needs to be at least twice as good as for a picture intended to be viewed on a monitor screen. The point of diminishing returns, for inkjet printers and normal human eyesight is about 240ppi, ie., increasing the print resolution much above this point tends to produce an imperceptible increase in quality. When buying a printer, don't confuse dots-per-inch with pixels-per-inch. It takes several dots of ink to make up a pixel, eg., a 1440dpi printer printing a picture at 144ppi is using a square of 10 x 10 dots to make up each pixel. The larger the number of dots used to make a pixel, the greater the range of tones or colours which can be reproduced, always assuming that the pixels are too small to be seen. When submitting image files to publishers incidentally, 300ppi or greater is the normal requirement.

Complete replacement of the conventional darkroom requires a computer, a scanner, a printer, and image editing software. The industry standard editing program is Adobe Photoshop. Cheaper altenatives also exist, and GNU/Linux users should take a close look at the GIMP project (GIMP has now also been ported to Win32). For printing, excellent results can be had using 6-colour inkjet printers, with products from Epson usually holding a slight technological edge. Affordable inkjet printers are available for A4, A3, and even larger sizes of paper; and special photographic quality printing papers are available to give the same surface finish as a conventional photograph.

Digital stills compact and SLR cameras have now reached a state of maturity, making 35mm and APS film effectively obsolete in countries where computer ownership is commonplace. There seems to be little public awareness of the density-range issue however, and so manufacturers and marketing strategists are still obsessed with image resolution. The real problem, from an image quality point of view, is that some cameras can only output 24bpp images, and worse still, some can only output images as JPEG files. True 35mm film quality from digital cameras requires lossless file compression and TIFF or RAW output at 36 or more bits-per-pixel, and you should check that this is what you will get before buying a camera.

Q: I might try to get my pictures published. What type of pictures do people want?

A: 300+ppi TIFF files. Past consensus has been that the best UW photographs are taken on slow transparency film (Kodachrome 25 or 64, Fujichrome Velvia 50, etc.), with a slightly low-key (dark on average) exposure to ensure best projection quality and colour saturation. Grainier, less saturated pictures are only acceptable if the subject matter is exceptional. Nowadays however, it is important to realise that most of the pictures used will be scanned into a computer, and it is sensible to choose film stock and exposure settings with this in mind. Low key images do not produce the best scans, even if you use a 36 bit scanner. For optimum scanning; exposures should be tailored to make full use of the contrast range of the film, and you might get better results by using slow negative stock (although the choice is limited). Such pictures can look flat (slightly bleached and lacking in contrast), but the appearance can be adjusted in the process of converting from 36 bits per pixel, down to the 24 bits per pixel used in the final image (ie, by using the scanner software, or by importing the 36 bit data into Photoshop and adjusting the image before converting down). It follows that scanning is part of the creative process, and should be under the control of the artist, but only if the artist owns a high-resolution scanner capable of 36 or more bits/pixel. It is better to send a slide or a negative, than it is to send a 24bit image file with an incomplete histogram or a bad contrast curve. A 36 bit scanner gives a factor of 16 redundancy in the data, and gives exceptional control over the final appearance. A 24 bit scanner gives no control whatsoever, and except for the occasional lucky shot, will always produces pictures with effectively less than 24 bits per pixel. If you adjust the contrast or colour balance of an image significantly after conversion to 24 bpp, you end up with large gaps in the histogram; and the image becomes posterised, unnatural looking, and unacceptable. Publishers who take pictures from amateurs will sometimes say that they prefer slides, but what they mean is that they don't want image files from cheap scanners, or from people who haven't mastered the scanner software and calibrated their equipment.

When your TIFF files are ready for release, you will then have the problem that they don't fit on to floppy disks. The only thing which is big enough, and which everyone can read, is a CD. A CD writer is therefore basic equipment for the digital photographer. You should give your pictures 8.3 type filenames, and burn the distribution CD in a single closed session, in plain ISO 9660 format; it will then be readable by all current PC, Mac, UNIX and Gnu/Linux systems. Alternatively, you can produce disks in Kodak Photo-CD format, but the software to do this costs extra.

The astute reader will have noticed, at this point, that I have not, so far, said anything about image content. Books abound on the subject of what should be in a good photograph; and if you want to target a particular medium, you need to get to know that medium. Some magazines only publish underwater pictures with divers in them. Others concentrate on wildlife, and some like the occasional arty shot. It's no good sending someone something which will bore the target audience, and your work has to be at least as good as the stuff you've seen already.

Q: Isn't digital image manipulation cheating?

A: Certainly; it's a thoroughly reprehensible activity and should be banned. Equally scurrilous is the practice of buying film from manufacturers, since it gives an unfair advantage over those who still boil up old bones and dissolve cutlery in nitric acid.

The fact of the matter is that photographic images have always been manipulated, right from the earliest days of photography. The main editing functions of Photoshop are based on standard darkroom techniques - it's just that photomontage, air-brushing, and re-touching, etc. are now easy to do. The fact that people no longer believe that photographs never lie is certainly good for democracy, and what one person believes is cheating, another will regard as part of the creative process.