Kitabı oku: «Collins Complete Photography Projects», sayfa 2

EXPOSURE

For most of our careers, correct exposure was the most important technical decision that we had to make because most of our work was on colour transparency film, and the quality of the image was greatly affected if it was overexposed by even +½ stop. It was safer to be –½ stop underexposed to give a rich, saturated transparency for reproduction.

Today, photographic technique is equally divided between the camera and the computer, so if you find your pictures are under- or overexposed you can usually correct that later with image-editing software. However, you do still have to be very careful not to overexpose a subject that has inherent bright highlights. As with transparency film, those highlights ‘blow out’ and lose all detail, and you will never retrieve any detail no matter how much you darken the area on the computer.

Underexposure of a subject with dark areas is not such a problem, as it is possible to retrieve an image underexposed by as much as –2 stops without adding much noise to the shadows.

UNDEREXPOSURE

This picture is underexposed by –2 stops. However, underexposure can often be used for effect – this exposure, for instance, could be used for an evening effect. If it is a mistake, this amount of underexposure can be corrected to almost normal.

CORRECT EXPOSURE

Here the correct exposure for this subject has provided detail from the darkest tones to the lightest highlights. Correct exposure is the ideal starting point to either use as it is or to add your own interpretation to on the computer.

OVEREXPOSURE

This picture is overexposed by +2 stops. Although it can be partially corrected later, the highlights, where they are pure white, will retain no detail as they are totally blown out and cannot be corrected.

HIGH KEY

The high-key effect is traditionally a black and white technique used for babies, children and glamorous women, giving a romantic interpretation of the subject. The lighting is as close to shadowless as possible. It is a good idea to have some small dark areas in the picture to contrast with the overall white tones. This baby picture is lit with soft overhead daylight that has eliminated most of the shadows, giving a soft, dreamy quality. It was overexposed by +1 stop to keep the highlights bright, using exposure compensation. 1/250 second at f5.6, 50mm, 400 ISO. GH

THE TECHNIQUE

The term ‘stop’ is used for referring to exposure. If you step up one stop you will halve the exposure, while if you step down you will double it. For instance, by moving the shutter speed up from 1/125 second to 1/250 second the exposure has halved (–1 stop). Moving down from 1/125 second to 1/60 second doubles the exposure (+1 stop). The same also applies to the aperture and ISO settings.

Your camera gives you the option of moving between stops in fractions of ⅓ or ½ of a stop. You will probably find that setting the camera to ½ step between the stops makes it a bit less confusing when using the shutter, aperture and ISO dials since it relates more easily to the doubling or halving effect of a whole stop.

LOW KEY

Traditionally used for masculine subjects to make a dark, moody interpretation, the low-key effect can be applied to many subjects. In this case the backlight encouraged me to underexpose the picture to get a dark, romantic feel, letting the backlight be used only to separate the lovers from the background. I used a 500mm mirror lens, which has made ‘doughnut rings’ out of the background highlights. I exposed for the highlights here, letting the shadows underexpose by –2 stops. 1/1000 second at f8, 500mm, 400 ISO. JG

UNDERSTANDING APERTURE

The aperture is one half of the exposure partnership. Together with the shutter, it controls how much light is exposed onto the sensor to form the image.

If you are new to using aperture and shutter speed controls, it’s a good idea to start with aperture priority (A or Av) mode. This will let you choose different apertures and you can watch the camera automatically select the shutter speed to produce a normal exposure. Find a subject with an object close to you in the foreground, one further away and another in the background. First shoot a picture of it with your widest aperture – f4.5, for instance – then stop down the aperture progressively to f16 for your next pictures. This will give you an illustration of how the aperture controls the depth of field – the amount of the subject that is in focus. Aperture is not only an exposure tool; the aperture we choose greatly affects our creative interpretation of the subject.

WIDE APERTURE

Here you can see a lens at its widest aperture – in this case f2.8.

NARROW APERTURE

Stopped down to f16, the aperture through which light passes is now greatly reduced.

SHALLOW DEPTH OF FIELD

To demonstrate the shallow depth of field that a standard lens will give when set at f2.8, I focused on the zebra. The animals in the foreground and background are out of focus, which has the effect of keeping our attention on the zebra.

WIDE DEPTH OF FIELD

This is exactly the same subject, photographed from the same distance, but stopping the aperture down to f16 has made everything sharp, from the cheetah in the foreground to the background tree. Every element in the picture is now vying for attention.

THE SHUTTER

The speed of the shutter is the other half of the exposure partnership, acting in tandem with the size of the aperture to control how much light reaches the sensor or film to form the image.

To get to grips with the function of the shutter, set your camera to shutter priority (S or Tv). The available shutter speeds will go from about 30 seconds to 1/4000 second. There is one more shutter setting, called Bulb (B), which can only be used when you are in manual mode (M). Here the shutter will stay open as long as the shutter release is kept pressed – a facility generally used for long night exposures.

Practise shooting at different shutter speeds, focusing on moving objects so that you can observe whether they are frozen in action or blurred. With speeds slower than about 1/60 second any camera movement will start to show as blur in the overall picture, so if you want sharp pictures at slow shutter speeds you will need to support the camera on a tripod or some object such as a wall or table. For hand-held telephoto lenses, assign a shutter speed that is at least as fast as the telephoto setting you are using – for example, a 200mm lens needs a speed of at least 1/200 second to avoid blur from camera movement. If you are using an APS-C sensor camera, you need to increase that to 1/300 second.

When you look at the photographs carefully afterwards, you will see that there is a considerable graphic difference between a picture in which a fast shutter speed has held hard-edged colour and shapes and one shot on a slow shutter speed, where the colour and shapes have become soft-edged.

FAST SHUTTER SPEED

The cyclist rode past the stationary camera, which was on a tripod. Exposure at 1/1000 second has frozen his movement.

SLOW SHUTTER SPEED

Here the exposure was 1/30 second as the cyclist rode past the stationary camera; the slow exposure has blurred the subject.

PANNING

Again the cyclist rode past and again the exposure was 1/30 second. This time the camera moved to follow his action, a technique known as panning. The result is that the cyclist is sharp and the background is blurred.

LENSES

The primary function of a lens is to focus the image onto the film or sensor. It also controls the angle of view and houses the aperture diaphragm.

You have a choice of using fixed focal length (prime) lenses or zoom lenses. The latter are designed to provide a range of focal lengths in one lens, with wide-angle zooms providing the shorter lengths and telephoto zooms covering the longer ones. Zoom lenses are almost universally used now because they reduce the amount of equipment you have to carry around. The advantage of prime lenses is that they have larger apertures and are the ultimate in optical sharpness. However, most of us would not be able to tell the difference in general application.

The decision as to what focal length you select for a photograph should not just be about encompassing more of the subject with a wide angle lens or getting closer with a telephoto. It is a creative decision based on the fact that lenses control perspective and also, linked with the aperture, dictate how much is in focus in front of and behind the point of focus – the depth of field.

The majority of the pictures in this book have been taken on DSLR cameras with APS-C sensors and the focal length stated in the captions applies to those, except where it is stated that the picture has been shot on film. To find the equivalent APS-C digital angle of view for the film images, divide the focal length by 1.5.

WIDE-ANGLE LENS

This is an example of a wide-angle lens at work. It has enabled me to get very close and look right into the ears of wheat in the foreground while still showing that this is a vast field of grain. Stopping down the aperture to f16 has kept the picture sharp from the foreground back to infinity. 1/250 second at f16, 24mm, 100 ISO film. JG

TELEPHOTO LENS

This is an example of a telephoto lens helping me to interpret the hunting scene the way I felt it looked. The long focal length has compressed the perspective, making the rear riders appear closer to those in the foreground than was the case. Shooting with a wide aperture has made the leading rider and dogs sharp, separating them from the out-of-focus background. 1/350 second at f3.5, 400mm, 400 ISO film. JG

CLOSE-UP PHOTOGRAPHY

This is a genre that some photographers get hooked on and it particularly attracts people with a scientific bent, because it is all about making discoveries. Most new-generation cameras will enable you to see your object at a ratio of 1:1 – that is, the object at its real size. If your lens won’t focus this close, you can buy either a macro lens or a close-up filter to attach to your existing lens.

AUTUMN LEAF

Close ups focus our attention on something that we don’t usually notice, in this case the beautiful structure of this leaf. Many modern cameras are able to get this close without a macro lens. 1/15 second at f11, 55mm macro, 200 ISO. GH

THE MACRO LENS

This is a demonstration of how I photographed the autumn leaf, using a 55mm macro lens. The selected portion of the leaf is life size, and it is backlit by a lightbox – a great method of shooting translucent objects. GH

POCKET WATCH

I shot this pocket watch using backlight from a window and my 55mm macro lens, with the camera on a tripod to prevent any camera movement. As we get closer to a subject we have an increasingly shallow depth of field, which means that on a picture such as this the lens must be stopped right down to a small aperture to maintain sharp detail over the area of interest. That requires a slow shutter speed to achieve a normal exposure, hence the tripod. 1 second at f16, 55mm macro, 200 ISO. GH

WHITE BALANCE

The white balance (WB) technology in digital cameras was developed to make every colour picture you shoot look as if it has been taken in neutral white light without a colour cast.

If you set the WB to Auto that’s exactly what the camera will do. However, this means that you will lose the golden cast of sunset light and the blue glow of dawn, and that’s certainly not desirable.

Today, we consider white balance adjustment in the camera as not particularly important, because it is so easy to adjust the colours in the camera or on the computer. We generally leave the WB set on Daylight and fine tune on the computer later. However, if you wish to match your WB to the light as you go along, here are your options.

Incandescent

Your normal household tungsten light is classed as incandescent. It is much warmer (yellow/orange) than daylight and requires the camera to add blue to balance it back to neutral. This gives a more neutral colour balance than Auto, which often tends to be too warm. Incandescent bulbs are being phased out, replaced by low-energy bulbs. The light from these bulbs is in a variety of tones of white, so you need to do a test shot to check the colour balance. One of the fluorescent settings may work best.

Fluorescent

When you are shooting in fluorescent light, one of the fluorescent settings will possibly give a better colour rendition than the Auto WB. Fluorescent tubes and low-energy bulbs come in a variety of colour temperatures. The Fluorescent WB setting usually gives you two or three choices; do a test shot with each and choose the best one for the light you are shooting in.

Direct sunlight

Like daylight-balanced colour film, this setting gives a neutral colour balance in direct sunlight in the middle of the day.

Flash

The light from a flash tends to be slightly cooler than daylight, so this WB setting warms up the light a little.

Cloudy

On overcast days the light is cooler. This setting warms it up slightly to match direct sunlight.

Shade

Light in the shade is much cooler than bright sunlight, because shade light is mainly indirect blue sky light. This setting warms the light to that of direct sunlight.

QUICK TIP

It’s worth playing around with each of the WB presets to see the effect they have on a single light source. Choose a subject and take a picture of it with each WB setting, then repeat with another subject in a different light source. Note which setting gives the most neutral balance and which one could be used for an effect.

THE WHITE BALANCE MENU

Choose the appropriate setting to match the light you are shooting in, or use Daylight and correct any colour cast with image-editing software.

DAYLIGHT WB

The musicians were shot in a subway lit by incandescent light, with the WB set on Daylight. As you can see, the light has photographed with an orange cast. 1/20 second at f5.6, 38mm, 400 ISO. GH

INCANDESCENT WB

Using the Incandescent WB setting has neutralized the orange cast, making the light look realistic.

DAYLIGHT WB

This portrait was taken in the shade, with the sky providing the blue cast. With the WB set to Daylight, the picture is far too blue. 1/125 second at f5, 24mm, 400 ISO. JG

SHADE WB

Here the Shade WB setting has added some warmth to neutralize the blue colour cast.

FILTERS

In the pre-digital days of shooting on colour transparency film, professional photographers carried around a large selection of light-balancing filters to correct the colour casts in single and mixed light sources.

With the technological advances in digital cameras, those filters attached to the front of the lens have largely become obsolete; most cameras now have built-in digital filters to simulate the effects they gave. Generally, these can only be applied via the retouch menu after the picture has been taken. Post-processing on the computer also provides the ability to adjust colour casts.

The two on-the-lens filters we still recommend you carry are the graduated neutral-density filter and the polarizing filter, especially when you are shooting landscapes. The ‘grad’ filter, which is available in varying densities and colours, will allow you to retain detail or exaggerate the sky tone in a landscape where the sky would be overexposed. This effect can also be done in the computer using Photoshop, but it requires some skill. Using a grad filter on the lens will give you an instant result. A 2-stop neutral density (grey) graduated filter is a good one for general use.

The polarizing filter is often used to darken blue skies and thus make the cloud formations more prominent. While that can also be achieved in Photoshop, where the polarizer comes into its own is in reducing or eliminating unwanted reflections from water, glass and non-metallic surfaces, which cannot be done on the computer.

QUICK TIP

Adding a diffusion or softening filter on the lens can be flattering for portraits, giving them a glow and smoothing detail. A similar effect can be added later in Photoshop or in Lightroom using the Clarity tool. Also try breathing on the lens to mist it up before you shoot – it can produce a very soft effect.

FILTERS

Shown here are a polarizing filter (bottom left), graduated filters (top left and right), and the lens mount (bottom right).

UNFILTERED

In this unfiltered landscape shot, the sky has been overexposed because the landscape, which occupies most of the picture, is darker than the sky. The camera is unable to handle the major difference in exposure. 1/250 second at f11, 75mm, 400 ISO. GH

NEUTRAL DENSITY FILTER

Here, the neutral density filter has been slid over the sky area, slightly cutting into the horizon line. This has enabled the capture of detail in the sky that was visible to the human eye. 1/250 second at f11, 75mm, 400 ISO. GH

UNFILTERED

In this photograph taken without a polarizing filter, the sky is reflecting in the water. The water is impenetrable, resembling opaque glass. 1/250 second at f6.3, 29mm, 400 ISO. GH

POLARIZING FILTER

Here a polarizing filter attached to the front of the lens was rotated to a position where it cut out the reflections of the sky, allowing us to see below the surface of the water. 1/30 second at f6.3, 29mm, 400 ISO. GH