A DECADE AGO, this month, I was in the Red Sea with a mad plan. I wanted to take a colourful image of the famous stern of the Giannis D.
The composition was a classic. The wreck’s rear end is exactly the right size for a vertical fisheye shot and we’d been shooting it that way since she crashed into the reef in the 1980s.
But the picture had always been monochrome blue, being too big and far away to light with strobes. I wanted a more colourful version and I had tried on my previous visit to the Red Sea, using a technique I was pioneering at the time using just manual white balance.
I could get the colour of the wreck but the white balance was sucking away the blue colour of the water too. I realised that I needed a filter.
The problem was that nobody made a filter for fisheye lenses. So I designed my own, by sandwiching three different gel filters together and sticking them to the back of my lens.
To hedge my bets, I actually made up two different recipes, giving my less-favoured design to my buddy Peter Rowlands to test. Post-dive, my shots were again too washed out, but Peter’s were amazing.
Fortunately we dived the wreck again on the following day, and with a small modification to Peter’s recipe I took the first photographs of the whole stern in full colour. Well, apart from Peter’s shots from the day before!

THE TRIP WAS ONE with friends from the British Society of Underwater Photographers. Everyone was very excited by the new shots, and over the week everyone who had a digital camera had tried it, the talented bunch producing amazing, strobe-free, colourful images of wrecks, coral seascapes and schools of fish. Far more uses than I had planned.
They also implored me not to keep the filter to myself and by August 2005 we were selling Magic Filters. Ten years on they are still helping photographers all around the world to produce new types of images and video.
Filters are an alternative to shooting with strobes, not a replacement. As with any technique, they are about adding another option to our arsenal of skills – something we should use with suitable subject matter, in suitable conditions.
The best subjects for filters are coral gardens, divers, wrecks, big pelagics and schools of fish. Filters work best on sunny days, when there is lots of light, although now that most cameras perform very well at medium and high ISOs they can be used in far more conditions than in the early days.
That said, filter photography works best when shallower than 15m, although with less colourful subjects, such as wrecks, we can push this a little deeper (Giannis D is in about 18-20m of water).

THE REAL KEY to shooting successfully with filters is to appreciate that it’s completely different to shooting wide-angle with strobes. With filters the golden rule is to always shoot with the sun on our back, so it comes over our shoulder and illuminates the subject.
The direction of light must be our first thought before every shot. This means that we cannot shoot every angle on each dive and we may need to dive a static subject, such as a wreck, at different times of day to get the perfect shot of every feature of interest.
Avoid taking filter shots towards the light or the surface, which will leave subject matter silhouetted without colour or detail and will also over expose, or white-out, the surface. With very wide lenses, such as fisheyes, we may find that a slightly downward camera angle gives the best results.

ALTHOUGH WE CAN SET white balance in post-production, we get noticeably better results if we set the camera’s white balance manually under water. This is because RAW files are not really as raw as we sometimes like to think.
Big adjustments to white balance in post do create noise and reduce the range of colours in a RAW file. We avoid these issues when right white balance (or close to it) is locked into the file at the time of shooting (meaning only minor changes in post processing).
It is also worth shooting RAW + JPG with filters, as many cameras process this type of image much better than third-party software such as Adobe Lightroom can. This is especially true of Canon cameras, which can add much more “tint” in camera than can be added within the limits of Lightroom.
Setting the white balance manually causes concerns, among SLR shooters in particular. Compact shooters are often more used to this technique and surely smirk at the fuss SLR photographers make!
The key is to practise on land (with the camera in the housing) so that you get used to the procedure for setting it. This does vary between cameras.

MOST EXCITING for photographers is that filter photography adds colour to images in a different way to shooting with strobes, and the best filter images are usually the ones that just can’t be replicated with strobes.
The question I get asked a lot is what is the advantage of using a filter, compared with just using the camera's manual white balance alone.
When you are very shallow, just below the surface, in the top 2-3m, then white balance alone is absolutely fine. However, once you are deeper than 3m the advantages of a filter become increasingly apparent.
The main advantages are more subtle variations of the colour and, most noticeable, that the foreground is set against a rich blue background.
Many photos taken with manual white balance are characterised with a washed-out background water colour.
A strong blue background is an important aesthetic element in an underwater photograph. Ask anyone what colour the sea is, and they will tell you that it is blue!
Finally, there is the hidden pleasure of filter photography to enjoy: leaving your strobes on the boat and enjoying the freedom of a manoeuvrable, compact rig. Ah, the joy of being a diver!

Sometimes filter shots can look a bit flat on the LCD screen under water. I have had photographers show me their filter shots after a dive, disappointed that they couldn’t get the filter and white balance working.
However, when they see the images again at the surface they are really pleased. So whatever happens, keep shooting!

Under water we can set white balance against a white slate or grey card, but most of the time a neutral-coloured section of reef or wreck is fine – as long as it is done at the same depth as the subject.
Common problems that cause trouble in setting white balance are when the camera is under-exposing the white-balance target, the target is in shadow, or we are too deep.

The most important factor with filters is to shoot with the light. Pay attention to how it is lighting the scene. It must be coming from behind us, lighting up the subject.
This lesson is the other great reward of filter photography. I am convinced that my wide-angle strobe photography under water improved dramatically when the discipline of shooting filters taught me to pay proper attention to light.