Thursday, 31 May 2007

Taking Underwater Pictures

Some of you who frequent this blog may have noticed that I do a little underwater photography and I thought I would pass on some thoughts about how to get the most out of being underwater and taking pictures.

First off, other than you have a camera, you are underwater, and the normal laws of physics apply underwater, there is little in common between underwater photography and topside photography! The main point to note is that underwater photography in the UK means a lack of light. The human eye is incredible in compensating for reduced light levels and it is only when you look through the viewfinder do you notice that the shutter speed of 1/60 at 15m has now dropped to 1/4 at 25m! In addition to this, the eye compensates for colour reduction without realising it too, and it is only when the image is reviewed on the surface do you note that the colour is gone!


Last January I was going on a trip to Tenerife and although I had 10 years plus of topside photography I had never taken a camera underwater, and I wanted to start. After researching the idea, I had my heart set on an Ikelite rig for my S2. After totting up the costs I realised that spending over 2 grand on something I might not like or enjoy was pretty daft, so bought an Olympus 5050 with Epoque 0.56 WA adaptor from Alan James Photography in Bristol. I then spent the rest of 2006 using this rig with some pretty good results. After I started doing more deep stuff, and also taking pictures of friends scootering around, I was seriously hankering for a housing for my S2. £350 later from Belgium my Aquatica housing arrived. £500 later I had an 8” dome port, gears and extensions. Another £1000 got me my 2 x Ikelite SS200 strobes from the USA plus some ULC buoyant arms from Cameras Underwater in London. The new rig now weighs somewhere in the region of 10kg on the surface and -1kg in the water.

If you are starting out in underwater photography and you own an SLR, I would personally hold off being a housing for your SLR until you have got your buoyancy nailed and you are used to using a camera underwater whilst maintaining awareness of your buddy, your environment and your gas. If you have got this nailed and you have £3k to spare, go and buy an underwater housing for your SLR, you won’t look back.

Basic Techniques

The most important bit is to get as much light as possible. Most of the shots that I have taken so far have been without strobes and so I have relied on natural light. Using the Olympus 5050, I could take advantage of the f1.8 lens and 200ISO to get the most out of the shots. Move to 400ISO and the image is very grainy and can only really be viewed in mono. Using the SLR I don’t have lenses which are as fast (the 10-20mm max aperture if f.35) but the noise levels in the shots are far less and therefore I can shoot about the same shutter speed but have a much larger and cleaner image. Whereas I would struggle to get a useable shot at 400ISO on the Olympus, the S2 at 1600ISO is perfectly acceptable for wreck/technical diving type images. If I wanted to get finer detail I would use a strobe and bring the ISO down to 100.

Another issue that is linked to light levels and depth is colour loss. Once you are past around 10m, images become very green and you need either a strobe or torch light to bring the colours back. Alternatively if the image is too green but you have sorted the balance out, then you can convert to mono which is what I do with a lot of my images. There are 2 ways to compensate for this colour shift if you do not have strobes; the first is to white balance the camera before you take the shot using a something which is white and ‘fooling’ the camera that this green tinted white surface is in fact white, the second method is to shoot in RAW which means the camera stores all the information but doesn’t have any final image, this is done in computer software topside.

If you are shooting natural light, always try to shoot down light such that it is over your shoulder into the subject’s face. As I said above, your eyes are very good at compensating and so if you shoot into sun the image will just show a big shadow from the areas being shaded as can be seen in this shot below; I really needed a strobe for this shot.

Photoshop Techniques

As I said above there is an issue with colour shift towards green when in UK waters. This means that the red and blue are absorbed quicker than the green, leaving you with a green image. There are some techniques which you can use in Photoshop to counter this. First off, shoot RAW and then use the grey scale dipper to get a neutral grey. This will get you very close to where you need to be and then you can play with levels after that. Otherwise, you can use the ‘Levels’ tool which can be found in most photo imaging programmes and adjust the light levels across the image. The following example uses PS CS for screenshots.

All levels.jpg, this is the original file. Taken in 15m at NDAC, Chepstow. As you can see this is quite green and fairly low contrast. This shot was taken at about 2m camera to subject.

Bring the black point (left hand arrow) and white point (right arrow) in until they meet the histogram. A histogram shows the dispersion of light quantities over differing intensities and colour channels. Here we are looking at the red channel, left is pure red, right is pure white (if this was all-levels, the left would be pure black). What we are trying to do here is make what light we have fill the whole spectrum. In the red channel you can see there is a lot of light missing, so we need to spread the light levels across and pick up the lost dark red.

Red Levels

Green Levels

Blue Levels

As you can see, as you spread the available light across the full spectrum, the image starts to get its full colour back again. However, the image is still a little flat so we add some contrast using the curve tool.

This makes the darker bits darker and the lighter bits lighter, the human eye likes contrast as it makes it easier to define edges and shapes.

RAW Images

This is what you can do with RAW images and why I will now always shoot photos in RAW if I can!

If you have any questions regarding my underwater photography or if you want some tips or help, drop me an email via my website which is listed at the top of this blog on the right handside.