DEAR BEGINNER ...

by Claudio Grazioli

1. The camera

The technological advances in digital electronics, and the wide range of accessories offered by today’s market, certainly encouraged the owners of compact cameras to underwater usage.

It often happens that, afetr buying a digital camera, later on they buy a housing. So, a new “photographic adventure” begins, that of underwater shooting.

That’s the way it all starts, using our camera in diving strolls, gathering simple souvenir pictures, and portraying the animals we meet.

Most of the times, when we buy a camera, we know very little about the basic notions of photography. We soon have to face problems with ambient light and underwater lighting, problems unknown to those who only shoot on land.

These few lines are addressed specifically to beginners, to remove a few doubts, and to convey simple concepts on what a camera is all about.

The simplest camera is nothing but a “box” with a hole, through which light passes, and, with light, an image. Well, our digital camera is ver much like a box, but with an objective, placed at the front, on top of the hole, for light to get through. The objective is a lens mount including a diaphragm, controlling the aperture.

The diaphragm makes it possible to vary the aperture (f), that is, the size of the hole, and therefore the amount of light reaching the sensor, and the brightness of the image.

The check whether we are opening or closing the hole, we can look through the front lens, and see how  the iris blades move to change the diaphragm aperture. If this seems awkward, we can use the LCD screen, looking at the f values that appear on it while we vary the aperture. These values decrease as we open the hole - e.g. from f16 to f11, or from f6 to f5.6 and down to f4 or f2.8 - and increase as we close the hole - e.g. from f4 to f5.6 or f8 to f11. In short, the higher is f, the smaller the hole, and vice versa, the smaller the number, the wider the hole.

Another important parameter is sensitivity, normally referred to as ISO. What is ISO? It is the sensor’s capability of reacting to the light that hits it to form the image. Let’s put it straight from the start: underwater, we must set low values of ISO, at most between 64 ISO and 200 ISO. This is contrary to intuition, because light is scarce down there. But we must still use low ISO’s because with high ISO we get poor contrast and high “noise”, which negatively affect the definition and clarity of the image.

Noise is an electronic disturbance, that interferes with the formation of the image on the sensor. However, in particular conditions, to make sure that we bring back home a picture, albeit of lower quality, we cain raise ISO from 200 to 400 or 800. We’ll have to accept a compromise.

The last parameter to consider is shutter speed, that is actually a time (T), the time it takes for the shutter to open and close when we shoot, expressed in seconds or fractions of a second.

In underwater usage, speed varies between 1/90 of a second and 1/250. We can use lower speeds, up to 1/60 or even (only for cameras allowing for this setting) to 1/30 without the ”blur” effect. This is due to the fact that water, being denser than air, acts as a mechanical stabilizer.

On the other hand, we must avoid high speeds when we use a strobe, because the camera may get out of sync and we end up with pictures marred by a black band, or the camera may even not shoot at all.

So, from this brief introduction we have learned that to control light, and image brightness, we must open or close the aperture,

set a speed, ans choose an ISO.

Usually, these operation remain unknown to a beginner, because she/he will tend to use tha camera in Auto or P mode (automatic programs), and all controls will be taken care of automatically by the camera, that will choose aperture, speed an ISO.

However, while on land we can get perfect images in automatic mode, underwater, things are much more difficult, you get wrong aperture values, blurred and dark images, because the programs fail to compensate for the different lightings of the various parts of the image. In dim light, the camera will tend to choose slow shutter speeds, and we will realize that not all cameras work correctly underwater. It all comes from the fact that camera are primarily built for on-land shooting.

To solve all these problems, we will have to learn how to use the camera in M = manual mode.

It is mandatory, at this point, to understand the correspondence between these three values, and to learn how to use them to the best.

They are mutually independent values, and with few simple rules we can handle them for a quick result. With time and experience, we will learn how to obtain more substantial achievements. They may seem difficult to grab at first, but let us take an empirical approach: let us dive at low depth, shoot, look, and correct our settings. Not casually, but with some systematic approach, like with a table that we have prepared on land, with fixed ISO and T (e.g. ISO= 100, T= 1/125). We would then vary f, depending on the distance of the subject.

Watching the image on the display is of great help, to correct the aperture at each shot, until we reach the optimum. After a while we will be able to single out the two or three preferred settings that will be used in the majority of the cases, and then we will learn how to adapt ourselves to particular situations, like white sand seabed (high light reflection - close the aperture), black rock (high light absorption - open aperture).

Recently, the technicians of the manufacturing companies have studied new systems to satisfy the needs of the consumers, loading the memories of the last-generation compacts with underwater programs, called SCENE or UNDERWATER. Using these programs, you may get good underwater images. However, if you use an external strobe, the pictures tend to become from reddish to red, with a preference for dominant “warm” tones, that will spoil the final result.

We are not claiming that all underwater cameras in auto mode perform poorly, but we can certainly get better results with the help of manual settings.

However, as an underwater photography instructor, I feel obliged to suggest that you attend a specific course on the subject, because I believe that with few additional notions you can quickly and substantially improve your  shots.

2. How to choose camera and housing

The verastility of a camera is very important: it amounts to its capability of adapting to the various needs of the photographer and to the type of housing he wants to use.

Probably, if you are a macro fan you will not buy a camera that won’t ensure an optimal magnifying quality; probably, you will avoid optics with digital magnification only, preferring a set of lenses allowing for optical magnification. In addition, not all cameras  have a dedicated housing, or a port for the favorite lens, and not all have a strobe that interacts  optimally with the camera system. Then, before buying a camera, you should carefully evaluate how you want to use it, what kind of shots you want to take, and to what extent you intend to use it underwater.

The “underwater camera”.

First, a few suggestions for beginners, particularly for those  who want to buy a camera directly for underwater usage. Obviously, you must make sure in the first place that an appropriate housing is available.

The minimal features required are the following:

Number of pixels of the sensor: 10 Megapixels (= millions of pixels)are more than enough;

Sensor: with equal number of pixels, a larger sensor should be preferred. Usually, compact cameras mount sensors with sizes  of 1/2,3” and 1/1,7”. In this case, it would be better to choose the 1/1,7” one (35% larger).

Recording format:  images in RAW format allow for  a finer processing  in postproduction (not indispensable);

Shooting speed: it is important that the shot and the actual formation of the picture be substantially simultaneous:

Image storage speed: the time between the shot and the loading of the image data onto memory should be al short as possible (it depends also on the type of memory card);

LCD screen width: a wide LCD screen makes it easier to frame the image and to read text and info  underwater;

Lens: choose a camera with optical zoom (not digital) and with the maximum wideangle focal. For example: better a  24-72mm zoom than a 35-105mm.

Macro: when you dive you meet an incredble number of small subjects, very interesting, and often very photogenic; you should prefer a camera that can afford macro shots. Pay attention to the focusing distance in macro mode. You should choose a camera with a housing allowing some clearance between the port and the subject, so that your flash can be positioned as appropriate as possible.

Power: a digital camera requires a lot of energy, so you should choose one with a  lithium battery. These batteries have a larger capacity compared to Ni-MH batteries, and allow for a higher number of shots with the on-board flash  (usually active on 99% of the shots).

Size/weight: obviously, a lighter and smaller camera body makes transport easier for our trips,  mainly by air.

Let us now evaluate the controls necessary for underwater usage. Our camera must have:

Shooting mode: it should be possible to use the camera entirely in  M = manual mode;

On/off switch: it must be possible to turn the camera on and off underwater.

Aperture: we must be able to set the appropriate aperture depending on the underwater situation;

ISO: it should be possible to change exposure sensitivity

with each shot, and anyhow to disable auto ISO;

EV+/EV- :  it is important to be able to choose  overexposure (more light) or underexposure (less light);

Flash: it must be possible to enable/disable the on-camera flash before shooting.

It is quite obvious that you must make sure, before you buy, that you can also buy an appropriate housing, to take your camera  underwater safely.

The underwater housing.

The housings come in polycarbonate, acrylic plastic, lexan plastic, aluminum, carbon, or a combination of different materials.

Each material has different properties: hardness, resistance to pressure, to corrosion, blows or scratches. They may show strengths or weaknesses with respect to weight, volume, and possible deformations due to temperature or pressure (at a depth of 40m, what is the approximate weight of the water column on every square centimeter of our housing? more than 5 kg !).

Many manufacturers directly build dedicated housings for their cameras. The market offers also “universal housings”, usable with various models of compact cameras, allowing us to obviate the interchangeability problems affecting dedicated models. We must point out that the features and the specs of he cameras are often assessed  without taking into account the housing.

This is a serious mistake, for we must always remember that the camera we are going to buy will be used underwater. Pay attention to the details of the camera, it must ABSOLUTELY possess some indispensable features.

Before entering into that, let me give you an example, to illustrate the problem.

There is a camera, of a well known brand, that, after a short time  (about 30 minutes) of inactivity, switches off automatically, to save battery charge. This could be a good idea, but unfortunately on the housing  there is no way of reaching the power switch from outside. It so happens that we insert tha camera in the housing, and we must switch it on before closing the housing. However, preparing the camera, getting ready for the dive and all may take some time. So when the time comes for the first shot, we may end up with the camera switched off, and no way to use it.

Furthermore, there are situations in which it is not recommended to have the camera switched on.  Think of having to do it on a rubber dinghy, crowded, and maybe with a rough sea.

On the other hand, if we had to switch the camera on long before our dive, and the camera didn’t have the automatic switch-off, after a long stand-by, we would find ourselves with no power. Think abou the idle times between two dives during a cruise, or on a seaside holiday, you easily end up with empty batteries.  

The first essential feature of a housing is therefore the possibility of reaching from outside all the key controls of the camera (listed above).

In addition it must:

resist to pressure: let us rule out all the housings with a resistance to pressure less then 5 bar (=40m of depth);

be capable of mounting accessories like: macro lenses, wide-angle add-ons for ambient shots, brackets for external strobes, etc.;

have  a limited weight and volume, for abvious transport reasons.