Cameras are becoming increasingly easy to use efficiently, as micro-electronic circuitry has taken over more and more of the important functions. Most of the key areas, such as focus, exposure measurement and film transport, are now usually automated. This automation frees the photographer's attention for more creative decisions, such as choosing the subject and framing the image. Provided that the camera user still understands what the machinery is doing, and why, this can only be for the good. The practical side of photography is very much a craft, and the camera is used best when the photographer is completely familiar with it. (Show Photo) Although in some ways it is a cliche to say that the camera should be an extension of the eye. Facility in camera-handling makes it possible to react quickly to changing picture situations. Their compactness and efficiency make 35mm cameras the most responsive of all types to rapid operation.
Focus
A single point in front of the camera is focused sharply as a point a short distance behind the lens. An entire scene, which is made up of countless points, focuses behind the lens on a, more or less, flat plane. Focusing a camera lens involves making sure that this plane lies exactly where the film is. There is nothing complicated about this, except that objects and scenes at different distances in front of the camera come into focus at different distances behind the lens. For this reason, a camera lens has to be movable. Distant features - the horizon line, for instance - focus close behind the lens. For nearer objects, the lens is moved forward, away from the film. As all modern lenses are compound, focusing usually involves the movement of some of the individual glass elements inside the lens barrel.
In traditional camera designs, focusing is done manually, the photographer checking the focus either visually (through the viewfinder of an SLR camera) or by means of a rangefinder. Most modern cameras, however, have automatic focusing: a small central area of the view is measured, the information is fed to a central processing unit (CPU), and this in turn activates a servo-motor that moves the lens into focus. The details of the operation are more complex than this, but the principle is straightforward. There are some differences between camera makes in how the focus is measured, but the usual method involves checking the contrast between the edges of objects seen through the lens (in an out-of-focus image these edges are blurred, so the contrast is less than when the image is sharp).
In most scenes, some parts will be nearer than others to the camera, and this has important implications on focusing. With the lens focused sharply on one object, such as a face, things nearer to and further from the camera will be out of focus to some extent. The degree of difference in sharpness between nearer and further objects depends on a number of factors, including the focal length of the lens, the aperture being used, and the depth of the scene itself. The depth of sharpness achieved in an image is known as depth of field.
Depth of field
The distance between the nearest and furthest points from the camera at which everything that appears sharp is termed the depth of field. In some photographs the lens is focused on a single element while everything else in the frame is noticeably out of focus. The result is that the attention of the viewer is clearly directed to the focused item. This is known as selective focusing (at least, when it is deliberate), and makes use of the difference in sharpness across the view. At the opposite extreme, if a photograph is sharp in both the foreground and the distance, the depth of field is great enough to cover everything. Focusing, then, is not so often just a matter of getting one thing sharp; usually, it is a matter of judging how much and which parts of a scene need to be acceptably sharp. In fact, whatever the depth of field, shallow or great, one particular distance will be more sharply focused than others. Whether or not this is noticeable depends on the eye's ability to judge sharpness. The limits of depth of field are not precise, but probably the most important way of controlling it is by the size of the lens aperture. (Show Photo)
Aperture
The amount of light that passes through a lens is adjusted by means of an aperture inside the lens barrel. The aperture's basic function is to adjust the amount of light striking the film surface to maintain the right exposure. In addition, it also alters the depth of field and therefore the amount of a scene that seems sharp. (Show Photo)
To standardize the aperture measurements between lenses, a system of f- numbers is used. A longer focal length of lens needs a larger picture than does a wide angle lens to pass the same amount of light. This would be hopelessly confusing if real aperture sizes were used calculating exposure. Instead, the sequence of f-numbers gives the relative aperture. The sequence reads: f1, f1.4, f2, f2.8, f4, f5.6, f8, f11, fl6, f22, f32, f45, f64, although any one lens covers only a part of this range. Each number in the sequence allows twice the exposure of the adjacent higher number, and half that of the adjacent lower number. Thus, f5.6 gives double the exposure of f8, and half that of f4.
The same f-number on any lens passes the same amount of light to the film. For example, on a 100mm lens, an aperture setting of f4 means that the actual opening is 25mm (100/4), on a 28mm lens set to f4 the opening will be 7mm wide (28/4). Because the image produced by lenses reduces in brightness in proportion to the increases in the focal length of the lens, this relative aperture system makes it simple for camera users to change lenses. The same f- number on different lenses gives the same exposure.
On lenses where the aperture is set manually, click stops mark each f-number. Although the numbers themselves may take a short while to become familiar, in practice, the halving and doubling is simple.
Reducing the aperture size has another important effect on the image; apart from altering exposure it increases depth of field. The more the aperture is stopped down, the greater the depth of field, so the aperture becomes an essential tool for managing the amount of sharpness in an image. For a quick guide, lenses have a depth-of-field scale engraved on the barrel, showing the distances from the camera (usually in feet and meters) within which everything will appear sharp at any given aperture.
When front-to-back sharpness is important in a photograph, the usual technique is to stop down the aperture. This in turn cuts down the light reaching the film, so that the photographer then has to turn to the camera's other exposure control - the shutter.
Shutter
Equally important for adjusting exposure is the shutter, of which there are two types used in 35mm cameras, focal-plane and leaf shutters. Like the aperture, exposure control is not its only function; the shutter speed determines the way in which movement appears in the image.
While leaf shutters work perfectly well with non-reflex cameras, SLRs need a different shutter system - one in which the film is protected from exposure even when the lens is open for viewing via the mirror and prism. For this reason focal-plane shutters were invented: a set of flexible blinds travel across and just in front of the film.
For manual operation, shutter speeds are arranged in a sequence that doubles or halves the exposure time, as follows: 1 sec, 1/2 sec, 1/4 sec, 1/8 sec, 1/15 sec, 1/30 sec, 1/60 sec and so on. Because shutter speeds, like aperture settings, are incremental, halving or doubling, aperture and shutter can be worked together. For example, widening the aperture by one f-stop (doubling the amount of light let in) and at the same time increasing the shutter speed by one step (halving the length of the exposure) keeps the same exposure. There is a reciprocal relationship between the two systems, and this has a bearing on the behavior of film at slow speeds. When the shutter is set automatically, as on modern, automatic cameras, there are no steps between speeds.
Apart from exposing the film, the shutter also controls the appearance of motion. A fast shutter speed "freezes" action, and one of the basic camera-handling skills is to judge the slowest speed necessary to prevent blur. Setting a speed that is faster than necessary requires an over-wide aperture to compensate. What determines the stopping power of a given shutter speed is how fast the subject appears to move across the picture frame. With a normal lens, the image of a car moving across the field of view at 50mph (80 kph) will flash rapidly through the viewfinder if it passes close to the camera, but may take many seconds at a much greater distance. Similarly, a change to a wide-angle lens will reduce the image size of a moving object, so the object's motion will be relatively slower in the frame. (Show Photo)
Stopping all motion is often assumed to be the ideal technique, and while it certainly gives the clearest image, it may not always be the most interesting or effective treatment. A slow shutter speed captures movement as a blur, and managed properly this can give much more of a sense of motion. Our appreciation of movement in everyday life comes from observing continuous sequences, and the still photograph that freezes one moment of this sequence can sometimes look static and odd. It is important to know the pictorial effect of various degrees of blurring, so that you can choose the result that best suits the situation.
Aperture/shutter priority
Aperture and shutter are to an extent interchangeable as controls for exposing the image. Where the lighting is dim or extremely bright (these are relative values, and depend very much on the sensitivity of the film) there may not be much choice in the settings, but over a wide range of light conditions there are likely to be several possible combinations that will give the same exposure, from a small aperture and slow shutter speed to a wide aperture in combination with a fast shutter speed.
This choice is valuable, allowing either good depth of field with the possibility of some motion blur, or selective focus together with frozen movement. There may be good reasons for favoring either of these effects, for instance, to focus attention on one object in a scene by means of a shallow depth of field or allowing a controlled amount of blur to convey the speed of a galloping horse. It is also important to have an appreciation of priorities. If stopping movement is critical, then some depth of field has to be sacrificed; if depth of field is more important, some blurring may be inevitable. In many automated cameras this choice is catered to in a selection of different programs.
Holding the camera
Modern 35mm cameras are designed for ease of use, but it still makes a difference to the operation if the camera is held and worked comfortably and efficiently. Like any tool, it performs best when handled with skill and familiarity, and the results usually show in the photographs- a faster, smoother operation means a better chance of catching fleeting images, and fewer technical mistakes. One of the main errors that good camera handling prevents is camera shake - the unintentional blur caused by jabbing the shutter or a shaky grip. Blur in an image is fine only if it is intended and obvious.
The grip for any particular camera varies, not just according to the make, but to the lens fitted, any accessories being used, and whether the framing is horizontal or vertical. Automatic cameras require fewer fingers for operation, and are likely to be easier to hold steady. As a general rule, the more experienced you are, the slower the shutter speed you can use without camera shake. This increases the number of picture possibilities. As an example, a shutter speed of 1/30 sec with a wide-angle lens, or even a standard lens, should be possible to achieve with practice.
Just as the shutter speed freezes or blurs a moving object, so the blur from camera shake depends on how much the image moves. A telephoto lens, which covers a small area of the entire view, is more susceptible to movement than is a wide-angle lens; the latter is always easier to hold steady at a slow speed.
Camera supports
Unlike large-format equipment, 35mm cameras are specifically designed for hand-held use, but below a certain light level (which depends on the film speed) some kind of support is essential. Even if you can handhold the camera without shake at slow shutter speeds, the depth of field will be shallow because of the wide aperture. A tripod, of which there are many designs and types, solves this problem. (Show Photo) Even in normal lighting, a long telephoto lens nearly always benefits from a secure camera support. Another important benefit from a tripod is that it allows precise composition. In a studio, or when photographing buildings or landscapes, for instance, a tripod not only permits fine adjustments to the framing, it actually encourages a more careful approach to picture-taking.
The disadvantage of a tripod is that it is an extra piece of equipment to carry around, which goes against the ethos of light, rapid 35mm photography. In general, the heavier and more substantial the tripod, the sturdier it is likely to be, though this depends on it being well designed and well built. A lightweight tripod may have an obvious attraction, but any camera support is only as useful as it is stable. Outdoors, the wind can make a flimsy tripod useless, while even the vibration of an SLR mirror and shutter can transmit a tremor to the image. In the studio, portability is not particularly important, so heavy tripods and even camera stands are usual. On location, the tripod choice is inevitably a compromise between weight and rigidity. Beware of cheaply constructed tripods with center columns that are raised and lowered by a ratchet and crank; although the idea is good in principle, this is often a weak point in a tripod.
Tripod heads demand separate attention, not only for rigidity, but also for ease of movement and convenience of attachment. There are two general types: heads with separate axes of movement (commonly pan-and-tilt heads) and ball-and-socket heads, which move freely in all directions when unlocked. Ball-and-socket heads are quicker to use, but more difficult to adjust precisely. Some tripods have a facility for fitting a lateral arm - useful for vertical copy shots.
A cable release (see Accessories below) further reduces the risk of camera shake, as does locking up the mirror of a SLR camera. The camera's self-timing shutter release is an alternative to a cable.
Accessories
Accessories comprise any ancillary equipment beyond the basic camera and principal lenses, and range from the useful to the gimmicky. While it is tempting to acquire accessory after accessory in the hope that each one will open up new picture possibilities, in reality there are only a few that are valuable. Modern 35mm cameras are designed to incorporate all essentials for normal photography. Of course, photographers with specialized interests, such as some scientific or nature subjects, have genuine needs for particular accessories. The following are among the more useful.
Lens shades: Flare degrades an image, even with modern multi-coated lenses. A lens shade, which cuts out extraneous light from outside the picture frame, will improve picture quality, particularly when the camera is aimed partly towards a light source. Some lenses have built-in lens hoods that retract when not needed; most take separate heads that screw or clip onto the front. The most efficient, though bulky, design of lens shade is an adjustable bellows that can be altered to suit the lens's focal length. Alternatively, a piece of black card, or even a hand, held close to the lens will shield it from a single light source, such as the sun.
Motor-drives and winders: Nowadays, these are only an accessory to basic, less- automated camera models, as most modern cameras incorporate a motor-winder to wind on the film after each shot. The value of a motor drive, which allows for continuous shooting, is that it permits fast action shooting; both it and the more usual motor-winder remove the delay and distraction of having to wind on the film after each exposure.
Filter holders: (See Filters in the "Lenses" Section). Makes of filter that are not designed to fit the lens diameter exactly, principally square or rectangular ones, need special mounts. The filter manufacturers normally supply these, whether for gelatin, plastic or glass filters, and they may sometimes double as lens shades.
Accessory shutter releases and triggers: There are a number of ways of operating the camera by remote control, whether from close to or some distance away, which may be useful in special circumstances, such as wildlife photography. The simplest is a pneumatic shutter release, although this alone has no provision for winding on to the next frame and resetting the shutter. Professional, electronic cameras and some others, have outlets for electronic triggering; the cable can in turn be attached to a remote device such as an intervalometer, which fires the shutter at pre-set intervals. Even more remote control is offered by a radio transmitter with a receiver attached to the camera. Light modulation is the basis of a simpler and less expensive system.
Viewfinders: Some SLR cameras have removable prism heads, which can be substituted for other types of viewing heads. A magnifying pentaprism head allows easy viewing of an enlarged screen without the need to press your eye up close to the camera. A waist-level finder is essentially a hood that shades the light from the ground-glass screen and is used for low-level viewing. A high-magnification focusing viewer also facilitates a right-angle view of the image, but is particularly useful for close-up or copy work.
Data back: A replacement for the normal camera back, this prints date, time and other information onto a small area of the film, usually by means of fiber optics.
Special attachments: These are available for fitting cameras to other types of optical systems, such as microscopes (see Photomicrography, in the "Wildlife" section), endoscopes, oscilloscopes and astronomical telescopes.
Panoramic head: This graduated rotating attachment fits between the camera and the tripod head, and allows precise alignment of a sequence of pictures taken as a horizontal strip. The alignment is always better with a longer rather than a shorter focal length lens.
Cases: A camera case prolongs the life of equipment. Solid cases, such as those of aluminum or ABS, gasket-lined and watertight, offer the best protection; some have adjustable compartments, others have foam blocks that can be cut to take a particular configuration of equipment. They are, however, more useful for transporting equipment from place to place than for working. A padded, shoulder bag with several compartments is more useful. There are many designs available, but the main criteria for choosing one is size. It should be large enough to take all the necessary equipment for normal shooting, but not so large as to be unwieldy. (Show Photo)
Cleaning and repair
Like any complex piece of equipment, a camera needs care and maintenance. A certain amount of this is common sense, such as keeping cameras wrapped when conditions are dusty or wet, and a regular cleaning regime saves camera repair bills later. Constant use, particularly outdoors, causes eventual wear and tear on all parts of the camera system. Lens surfaces, the electronics and moving parts are particularly vulnerable. For external surfaces, use a small brush (preferably a blower brush), lens cloth or tissue, and cotton swabs moistened with de-natured alcohol rather than water; a can of compressed air is also effective for removing dust and grit.
On-the-spot repair is becoming less and less possible as 35mm cameras become more automated and more reliant on miniaturized electronic circuitry. Breakdowns normally mean that the camera cannot be used until has been sent to the manufacturer or dealer for professional signal repair.
