Kitabı oku: «Collins Complete Photography Course», sayfa 3

Sharpening

• This function gives your pictures an appearance of greater sharpness by emphasizing the borders between light and dark areas. Whether and how much you sharpen in the camera is a matter of personal taste and also the subject matter. Sharpening is more suited to architecture than baby pictures, for example, though you can choose different degrees of sharpness. If you plan to work on the images in Photoshop later, it’s best not to sharpen in the camera but to leave it as the last step after you have retouched and resized the image.

Using a card reader is a quick way of transferring your pictures from the memory card to your computer.

Downloading the images from your card into a portable storage device such as this makes a secure back-up copy and is a way of managing your pictures on location.

Film effects

• If you want a digital image to look as if it has been shot on a particular film you can use software that will mimic the appearance of any film available now and even some obsolescent ones. Films such as Fuji Velvia, Kodak TriX, Ilford Delta and many more can be reproduced in Photoshop using software programs.

Film quality

It’s a mistake to write off film as a dying technology – in fact there is probably a greater variety of films available than ever before. While digital technology has been motoring on, film emulsions have been improving too. New films have been launched and some old discontinued films have been revived; at the same time the current favourites are still being improved.

The processing chemistry that goes with black and white film has been improved also and there are several small manufacturers making traditional formulae that have not been seen for years. This revival is directed toward the art photography movement.

Some photographers working in both colour and black and white prefer to shoot film and then go digital by scanning the negative into the computer and fine-tuning the image there, combining traditional and modern technology.

Black and white film

The actual speed of black and white films is dependent on the amount of development they receive – for example, a film that has a manufacturer’s rating of 400 ISO can have a working speed of 1600 ISO if the development time is increased sufficiently. Longer development times increase grain size and contrast. There are films available designed specifically for uprating, known as push films.

Black and white films are available in the following categories:

Slow-speed films: 20 to 50 ISO This group of slow films produces the ultimate in photographic technical excellence, giving very fine grain and high resolution (sharpness) and contrast. Use them for any subject that would be especially enhanced by those qualities, such as architecture and still life. Ilford, Adox and Rollei make films in this category which are superb when matched with the manufacturers’ recommended developers.

Medium-speed films: 100 to 200 ISO Films in this versatile group offer most of the qualities of the slow films in terms of fine grain and high resolution but are not as contrasty. This enables them to produce more shadow detail, which is useful for subjects such as landscapes and portraits. Ilford, Kodak, Fuji, Lucky, Adox, Foma and Rollei all have films in this range.

High-speed films: 400 ISO This group is the most versatile of all, and the manufacturers have been improving their films continually over the years. Ilford’s 400 ISO film started its life as HP3 in the 1950s, became HP4 then HP5, and has now graduated to HP5+, its latest manifestation in a long and distinguished career.

Today, all the 400 ISO films can be pushed up to 1600 ISO and beyond. At 400 ISO they reproduce a huge tonal range and can be used for almost any subject, which has made them the universal choice for photojournalists for many years and has also made them popular for landscapes on medium- and large-format cameras. As well as Ilford, Kodak, Fuji, Foma and Rollei all have films in this range.

Ultra high-speed films: 1600 to 3200 ISO These are all push films which can be rated at anything from 200 to 50,000 ISO, according to development time. The more you push them the grainier they become, with increased contrast. Use them for available light pictures and for when you want grain for graphic effect. Ilford, Kodak and Fuji produce them.

Chromogenic films Designed to be processed in C41 colour chemicals, these films have the advantage that they can be quickly processed with colour negative film in a mini lab. Although the negative looks different, they produce a normal black and white print. They are made by Ilford, Kodak and Fuji.

Infra-red films These films are like normal black and white films except that they have an extended red sensitivity. Foliage and faces become pure white when infra-red film is used with a deep red filter – to get the greatest effect, use an 87 or 88 Wratten filter to cut off all visible light relative to the infra-red. Exposure readings are difficult, and you will need to do a wide bracket (see p.32). Ilford, Rollei and Adox make infra-red films.

Digital transfer film This is a transparent film with a surface to accept inkjet printing, allowing you to make larger negatives. Makers include Permajet and Pictorico.

Colour film

Transparency films Colour transparency or slide film has been the traditional colour film for both the professional as well as the family slideshow evening. It has been preferred for the highest quality commercial printing. Most of the big transparency processing labs have now changed over to digital work, but transparency film still has many devotees.

Kodak films start from Kodachrome 64 ISO, the sharpest 35mm fine-grain colour film available. Their Ektachrome range starts from 64 ISO and goes to 400 ISO in steps of 100, 200 and 400 ISO. Kodak also make 64T film, a 64 ISO film which is balanced for use with tungsten light.

Fuji’s slowest colour transparency film is Velvia 50 ISO, which is highly saturated and has fine grain. Velvia is also available at 100 ISO, along with Astia and Provia 100; the latter also comes at 400 ISO. The Velvia films have a warm colour balance, while Asti and Provia are more neutral. Fuji also provide a tungsten-balanced 64 ISO film.

Kodak 200 ISO transparency film (left) and Fuji 400 ISO colour negative film.

Colour negative films There have been great improvements in colour negative films over the last ten years; the colour is more accurate, and the grain is smaller and sharper. Most photographers still shooting colour film are using colour negative, which has the advantage that a print can be made in the darkroom or it can be scanned and used digitally.

Kodak make a range of Portra professional colour negative films at 160, 400 and 800 ISO. These are available with a neutral colour balance (NC) or with more vibrant colour (VC). They also have a large range of amateur films from 200 to 400 ISO.

The Fuji Superia range covers 100, 200, 400, 800 and 1600 ISO. These films are warmer in colour and sharper than the rest of their range. The Pro range, from 160 to 400 and 800 ISO, is good for a general range of subjects, while Reala 100 ISO has finer grain and lower contrast.

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.

Lenses come with fixed focal lengths (known as prime lenses) or as zoom lenses. The latter are designed to provide many focal lengths in one lens, which reduces the amount of equipment that a photographer has to carry on location.

The advantage of prime lenses is that they have the largest apertures, allowing you to work in lower light levels without a tripod and to choose a shallower depth of field, which is useful in selective focus imagery. They are also still the best in terms of sharpness and minimum distortion.

Within these two categories there is a further choice between digital (D) and analogue lenses. The former are dedicated to digital cameras and will not work with film cameras; however, the latter can be used with both film and digital cameras, which means that if you are changing from film to digital you won’t have to go to the expense of buying new lenses.

Perspective correction lenses are used for eliminating the distortion that occurs when you photograph a tall building from a low viewpoint. The front of the lens can be moved up, down and sideways while the camera remains on the same plane. These lenses are mainly used by photographers specializing in architecture.

Focal lengths

While the sensors of DSLR cameras vary, they are approximately two-thirds the size of a 35mm film frame. This means that lenses are effectively increased in focal length by 1.5x, so that, for example, a 50mm lens will become a 75mm lens on a digital camera and a 200mm lens has the effect that a 300mm lens would have on film.

This means that there is an advantage at the telephoto end of focal lengths but a disadvantage in wide-angle lenses because a 24mm lens on a film camera is only about 36mm on a digital camera. To get a really wide-angle effect you need a 12mm or 14mm lens for digital, of which there are now plenty available.

Lenses range from an 8mm fisheye right up to 2000mm. There are also some very specialized lenses such as the perspective control lens and macro lens. Today, zoom lenses are used almost universally by most photographers, although some still prefer to work with fixed focal lengths.

You’ll find that just two lenses, a wide-angle zoom and a medium to telephoto zoom, will cover most situations. Indeed, the majority of people never use anything other than a zoom because cameras are usually sold with a zoom lens included, and they are also the easiest, lightest way to go. However, if you are interested in close-up photography you may want to consider using a fixed focal length macro lens as the quality is superior to that of the macro setting on the zoom lens.

Macro lenses are the sharpest you can buy. Most are about 55-60mm focal length, used with film; their focal length is effectively increased by 50 per cent on a digital camera. They are relatively inexpensive and you will probably be able to find a secondhand one at a good price on eBay.

Photographers keep to their favourite lenses over many years. It is often not so much that there is anything particularly special about that lens, but that it suits the way they see the world and the type of work they like to do.

Good-quality lenses, especially those with large apertures, can be very expensive. However, independent lens manufacturers such Sigma and Tamron make high-quality lenses for most DSLRs at about half the price of the camera manufacturers’ lenses.

Focusing modes

Your lens is focused via three modes that are selected from a switch on the camera body: S, C and M.

• S Single auto will automatically focus on the object that you point the camera at when you push the shutter button halfway down. It will fix that focus until you release the button or take a picture.

Reflex telephoto lenses have an internal mirror system and fixed aperture. Their creative characteristic is that they turn out-of-focus highlights into doughnut-like shapes.

A recent addition to some lenses is vibration reduction (VR), which allows you to shoot with lower shutter speeds and still get a sharp image. VR may be incorporated in the camera body instead of the lens.

• C In continuous auto, the camera will follow focus on a moving object when you keep your finger halfway down on the shutter button.

• M In manual mode the camera is focused by using the focusing ring on the lens. The focus indicator dot will light up when you are in focus.

Most DSLRs give you a choice of where to place your point of focus in the viewfinder. This could be a single point that you can move around the viewfinder and place where your subject is. Alternatively, you can group a number of the points together to cover a larger focus area in the viewfinder. This varies with different camera models.

Focusing modes

Focus lock

You will also have a focus lock on the camera. This may be a question of pressing the shutter release button halfway down, or there may be a separate button.

Exposure

The two devices that the camera uses to make an exposure are the aperture and shutter. Working in tandem, they determine the amount of light that creates the image when you release the shutter.

The aperture

A camera lens contains an iris diaphragm, based on the functioning of the iris in an eye. It is constructed of metal leaves that open and close, making a bigger or smaller aperture in the lens through which light enters the camera. The aperture thus controls the volume of light that’s allowed to reach the film or sensor.

The size of the aperture is calculated in f-stops. Confusingly, the smallest number on your lens, such as f/2, is the largest aperture, and the highest number, perhaps f/16, is the smallest. The reason for this is that these numbers are actually fractions, representing the focal length of the lens divided by the diameter measurement of the aperture.

The shutter

Located in the camera just in front of the film or sensor, the shutter controls the length of time that either is exposed to the light entering through the aperture. The main shutter speed settings are in steps, each of which halves or doubles the length of the exposure; for example, 1/250 second allows half the amount of light through the lens as 1/125 second, while 1/60 second allows twice as much.

Modern cameras have a large range of exposure time settings, from 30 full seconds to 1/8000 second. There is also a setting called either B or Bulb, which keeps the shutter open for as long as the shutter release button is held down (you will need a cable release or remote control to keep the shutter open for an extended period). Shutter speeds on the dial are in fractions of a second until they reach 1” second, the symbol “ denoting full seconds.

Your camera has different shooting modes: S (single), which takes a single frame each time you press the shutter release and C (continuous), which is a built-in motor drive that can take up to 6 frames per second (depending on your shutter speed) while the shutter button is held down or until the film is finished or the card is full. This continuous mode can be great to use when you are panning or trying to capture a fast-moving subject. Some cameras offer the option of low and high speed continuous shooting (CL and CH respectively).

Shooting modes

All these aperture and shutter combinations have produced the same exposure for this picture. If either element of the combinations were to be changed the image would be brighter or darker.

1/250 second atf/4

1/125 second at f/5.6

1/60 second at f/8

1/30 second at f/11

1/15 second at f/16

The aperture and shutter function in relationship to each other, because in order to maintain what you or your meter calculate to be accurate exposure, both the volume of light entering through the aperture and the length of time the film or sensor is exposed to that light must be adjusted. If you increase the volume of light by enlarging the aperture, to maintain the same exposure you have to shorten the shutter speed.

Exposure meters

The exposure is calculated by your DSLR or SLR camera’s built-in exposure meter. When you compose a picture in your viewfinder, the meter analyses the light reflected off the subject and calculates what it considers to be a correct exposure of that subject.

When you are using the P, S and A modes at least part of the exposure is automatically made by the camera. In the case of M (manual), you have to set both the aperture and shutter yourself. Whether or not your photograph will be correctly exposed at the settings you have chosen is shown in the display in the viewfinder’s control panel so that you can adjust them if need be.

Although built-in meters in good-quality cameras are now very efficient, some photographers still prefer to use a separate handheld exposure meter. These use two methods of analysing the light and making exposure readings: like the camera’s meter, they measure the light reflecting off the subject, or they can measure the light falling on it, which is called an incident light reading.

When you are working with the exposure in M (manual) mode the exposure display in the control panel of the viewfinder shows if your picture is correctly exposed and, if not, whether you need to allow more or less light.