Divers' Digital Darkroom
Post dive expectations often take a knock when those precious downloaded photos turn out to suffer from some classic problems. Pictures which look great on a 2.5” LCD rarely look better when you get back to your PC, so perhaps we should cover a little ground on how to make the best of what you bring back. For some people, images straight from the camera may be enough, but I hope the following will tempt you into the digital darkroom where bad photos can be rescued and good ones can be polished. Diving is supposed to be an enjoyable hobby, dive time is expensive and short – so enjoy your dives first, worry about pictures later.
My pictures are all green (UK) or blue (tropical). I thought flash would cure that!
A normal camera's auto white balance setting can't cope with the odd colour of light underwater. Maybe you or the camera chose not to use flash on a close subject or you were too far away for it to have any effect (in which case your picture may be both green and spotty – see “Snow, Backscatter, White Blobs”.)
Many photo software packages have a white balance or auto colour function. This will try to make the darkest parts of the picture black and the brightest parts white. The result of this is to approximate ideal exposure, but often these functions are overwhelmed by just how monochrome dive photos can be and can yield horribly red results. If they work, great; if not then some more manual interference may be needed.
What these functions aim to do is what is called 'histogram equalisation'. They struggle with dive pictures, because there is almost no red in them. If you go to the 'histogram' control in something like Photoshop you will be greeted by the inner workings of these 'one stop' functions. Those workings can be quite scary, but stay calm. What you are aiming to do is stretch each colour graph so that it starts at the right and ends at the left... give it a go; the 'undo' button was made for moments like this! As you are an intelligent being, you will be able to see when the effects stop being beneficial and start cooking your picture. You may have to moderate how much you boost the reds. Remember, it is not possible to make all pictures perfect and sometimes you may have to concede defeat. If you can't get the colour right just turn it off – black and white is always in fashion!
Snow, backscatter, white blobs?
Even clear water has small bits floating in it, even air does sometimes, and those bits can reflect light straight back at you - lighting them up like snow in headlights. When this completely covers the subject you are snookered, if they are just over the background or less important areas you stand a chance of rescuing the situation.
If the white blobs are distinct from the subject they can sometimes be removed by a scratch or dust filter, a more advanced option is to retouch or heal the holes they make in your picture.
Scratch filters work well on small, sharp specks, but not so well on large, soft blobs. They can also soften picture details and remove them wholesale. Retouching and healing tools are much more selective – you tell them where to work. This can make them laborious to use but the results are excellent. You may need to practice to get a clean picture but it's cheaper than buying an external strobe (which is the best fix of all).
If you want to look behind the way these tools work then the 'clone tool' is the manual version of this and can work when the clever tools choke. Essentially you copy ('clone') good parts of the picture to replace the bad. This needs practice but can also be used to remove spots from teenagers and ugly relatives from weddings so it can be very useful…
Blurred and out of focus?
It is quite normal for autofocus to struggle underwater in the same way as your eyes take time to adjust to very low levels of light. Dark, murky water is particularly hard to see sharp detail through and the camera will struggle like you do. Casting more light on the subject is one way to help and there are some very small 'focus lights' which can make a very big difference, particularly close up.
It is very difficult to recover badly blurred pictures. Once a photo is blurred you cannot expect to produce a poster sized masterpiece from it but often small versions will appear OK. Those smaller versions can be more responsive to sharpening, but you need to be careful not to try too hard or the photo will look very rough.
There are several methods to try, sometimes a 'sharpen' option will work OK but the tool most nerds use is the mysterious 'unsharp mask' which has three indecipherable controls. Don't worry too much about their names and play first with 'strength' which is the most important and most obvious. The others are useful but justify more space than I have here. Try them, they can make subtle improvements when used sparingly.
Too far away?
If your chosen subject is dwindling into the background or your camera simply couldn't get any closer the relentless march of mega pixels may be able to help you out.
As long your photo is sharp(ish) even quite small parts will look fine online or even used for small prints. You can crop away more than half of a 7 or 8 Megapixel picture and still be left with enough information for an A4 print. Even though the huge 10,12 and 15 Megapixel pictures produced by today's cameras aren't much sharper than the best pictures from a few years ago, grainy noise is becoming a thing of the past. In extremis, for an adequate Facebook gallery picture you could crop away 99% (Unbelievable isn't it!) of the pixels from a 15 Megapixel photo!
It's not usually worth cropping quite this hard, but almost every photo manipulation program will let you crop your pictures. This can be handy to pick out a useful small part or to improve composition by shifting the emphasis. Take care that your crop is a suitable shape, most cameras are 4:3 (old style TV shape), SLRs are 3:2 (which isn't really the same shape as anything else) and paper varies in shape horribly!
With these four fixes in mind most holiday collections can be turned into an attractive gallery or posted to Facebook etc. without embarrassment.
Polish up those underwater photos
As well a rescuing the walking wounded, a little computer time can improve most pictures. Snooty 'pro' types might sneer at fiddling but most of them will dignify some basic tweaking by describing an 'S curve' adjustment as part of their workflow. In fact, a little curve work will spice up most pictures making them more punchy and improving their colour, but you don't have to be a Photoshop wizard to do it.
How to fix your levels
Curve adjustment is just a grown up way of playing with the contrast of a picture; Pros will imply there is something considered about it, but in essence they are just making sure it looks properly exposed. As I said in the first chapter, auto controls often choke on sickly underwater pictures but they love half decent ones – a quick click on auto levels while watching a histogram display will show you exactly what is going on – dark areas are made black and bright areas taken toward white. The result is a punchy picture which looks sharper and more alive. If you can find the manual controls for this process then you can moderate its enthusiasm. Sometime this might appear as highlight and shadow controls – just watch a histogram as you stretch the picture from black to white.
Auto colour... underwater?
Again if you have a good picture some Auto Colour processes can work well. What they want to do is make the brightest and darkest parts of your picture neutral (uncoloured) in the hope that the rest will fall into place between. Sometimes this will help. At other times, a hint is needed and many programs include the option to tell them which part should be white (or black and maybe mid grey). This usually takes the form of an eye dropper icon which can be used to sample the point of the picture which should be neutral. These 'Auto' processes tend to make greenish cold water look blue... a nice effect but not always realistic. Look for a fine 'Colour temperature' adjustment to get the look you want.
Look around the picture for something which really was neutral – parts of a wet suit, properly exposed parts of aluminium air cylinders, even the sides of fish! Sometimes you may find that a dodgy picture has blotchy colourful noise in these areas, so you may have to try several times to get the right spot – zoom in to make it easier. Don't, however, mistake areas of blown highlights for white, these can confuse the process horribly. Once you have succeeded once or twice you'll see just how this works and never look back :-)
If you watch what these processes do to your photo's histogram, a graph of how the picture information is spread from black to white, you will quickly appreciate that a lot of this could be done quickly and accurately without even looking. The weirdness of underwater colour does unfortunately mean that even the cleverest 'one click' processes can be caught out, so supervising them is vital... and can be great fun. Often it's easiest to use them to get an idea of what potential a picture has and then to fine tune the final tweak yourself. Go for it, but use a copy not the original!
Underwater Photography Round-Up
In an ideal world every picture would be perfect straight out of the camera, but if that was the case photography would completely lose its appeal and become artless recording. There is always more to be drawn from a subject and always another way to look at the world which a soulless algorithm can't imitate.
Developing your pictures long after pressing the button has been part of photography since it was invented. Finding new ways to capture the feeling rather than the fact of what you saw has kept people busy for just as long. Some pictures are beyond saving, but once in a while you will take picture which has the potential to be not just rescued, but transformed into something special. If you have something like this, it is worth revisiting it as your darkroom skills develop, one day you may be able to unlock that latent image.
My favourite example of this is a picture of two Picaso triggerfish taken in just a metre of water on the last day of an otherwise rather bland trip to Sharm El Sheik. The composition was perfect – thanks to the fish not my judgement – but the background suffered from horrible blue noisy artefacts from the camera I had at the time. Try as I might I couldn't get it to work as a large print, the background looked grainy, blocky and spoilt forever. That was until a few years later when I had been working with layers masks in Photoshop, recalled that picture and realised what I had been doing would finally release my triggerfish.
Twenty minutes later I finally had a version which lived up to its promise, since then it has been popular in exhibitions, competitions, 'borrowed' for websites and for one of my friends it captures her first blue water holiday to a tee.
Note: It's very hard to show all the subtleties in such small versions of these pictures, so make sure you explore each idea youself!