SLR cameras get their name from the way they work. The light entering through the lens is reflected in the mirror and – after going through the prism – goes to the viewfinder. The mirror is raised when the photo is taken, lets in light from the lens and directs it straight onto the photographic film. A SLR camera gives the photographer much more scope than a digital compact (popular slot machine). We can set several parameters ourselves, affecting the appearance of the photo (e.g.. exposure time, or sharpness), and also exchange lenses, to make it easier to frame photos. Choosing films with the appropriate sensitivity, we can easily take a photo in different lighting conditions.
Lens. Most SLR cameras are equipped with interchangeable lenses with different viewing angles. In many cases, we only buy the camera itself (without lens) – i.e. the so-called. body, and we choose the lenses ourselves. The angle of view of a lens depends on its focal length given in millimeters. The smaller its value – the larger the image section we see in the viewfinder. So to cover wider images you need lenses with shorter focal lengths, and for "approximation” remote objects – about longer ones. Zoom. SLR cameras are usually factory-equipped with a zoom, i.e. a lens that allows smooth focal length adjustment (e.g.. in terms of 35-100 mm). If we want to cover a very broad plan, let's use a wide-angle lens (short focal lengths, e.g.. 28 or 18 mm); if we're going to take close-ups of very distant objects – let's get a telephoto lens (long focal lengths, e.g.. 400 or 600 mm).
In each lens you can set the sharpness of the image you see – the focus ring in the lens body is used for this. Cameras often have elements that facilitate precise focusing. These are:
• mikroraster – allows you to accurately focus the entire frame. In the lens we see a field composed of tiny crystals-squares. If the crystals form a clear image, the frame is sharp;
• dalmierz ogniskowy – is used for precise focusing of details. Looking through the lens, we see two circles with a common center. We check sharpness, directing them to the framed detail. If part of the item is shifted (as if "pushed out."” from the whole) – it means, that you need to adjust the focus.
Most cameras also have an auto focus feature (called "autofocus" or ,,OF"). The microprocessor takes the appropriate measurements and, on their basis, rotates the focus ring with a motor. Shutter. This is used to adjust the size of the lens opening, through which light enters the camera. Adjustments are made by turning the ring on the lens. The aperture affects the final appearance of the photo in two ways. First – its brightness depends on it (the larger the aperture – the brighter it is). Second, it decides, how much of the shooting scene will be in focus, and what – fuzzy. If we choose a large shutter opening – objects in the foreground will be in focus, and the background in depth – fuzzy. Aperture and background with a small aperture, and foreground are photographed with the same – high sharpness.
In most SLRs, we can give up manual setting of the aperture and outsource them to the camera electronics, which will take the necessary measurements and adjust the size of the opening to the lighting conditions, shutter settings and the nature of the picture taken (e.g.. panorama, rapprochement). Snapshot. It transmits light from the lens to the film and allows it to be exposed. By setting the shutter speed we decide, how much time the film will be exposed. This allows you to take pictures with the correct brightness under various lighting conditions. We use slower shutter speeds in low light conditions; with a stronger one – shorter. It also allows you to register the movement of the photographed object: sharply, in the form of a frozen cage – at very short times and in a blurry form – with long times. The shutter speed in modern SLR cameras ranges from a few seconds to 1/4000 parts of a second. Almost every camera also has a "position B" function, where the shutter remains open as long as it is, as long as we keep the camera trigger pressed. This mode is most often used when taking photos at night, when we need a very long exposure time. The shutter speed is set with the knob on the camera casing. It can also be automatically selected by the electronics of the camera.
The flash lamp. Many models have a built-in flash. Their manufacturers indicate the lamp synchronization time. This is the maximum shutter speed, what we can set, using a lamp. Usually it is 1/90 or 1/125 seconds.
Battery. Special standard camera batteries are used to power SLRs. One set costs approx 40 PLN and is usually enough to "stick out" 3-4 film rolls.
Let's remember the burden, that the equipment is heavier, all the more troublesome to wear, but also more stable, so the shake of handheld shooting will not have a big impact on the sharpness of the photo. Average weight of SLRs, it's about 0,40 kg.
Film. In SLRs, we use a film of width 35 mm. We can use black and white and color films, and such, which allow you to make slides. Each film has its own sensitivity measured in ISO degrees. Average sensitivity for black and white movies is ISO 125, and for the colored ones – ISO 100. Less sensitive films (ISO 50, ISO 25) give the best photo quality, but they require slower shutter speeds or larger apertures and very good lighting conditions. Movies with higher sensitivity (e.g.. ISO 400) characterized by visible grain (photos are less sharp), but they allow you to take pictures in not the best lighting. There are also high-sensitivity films (e.g.. ISO 1200, ISO 1600, ISO 3200), which is used to photograph dark interiors without the use of additional lighting and flash. They have thick, visible grain, but that does not have to be their disadvantage – we can like such artistic effects.