Most cameras of the lower consumer range, as well as many smart phones, do not offer any settings other than the fully automatic mode. If for you photography goes beyond just capturing some cherished moments of your everyday life and if you wish to achieve more interesting and artistic results, you need to buy a camera which gives you the opportunity to control at least to some extent the automatic operation of your camera. Often when we shoot sunsets, sunrises and landscapes we are struck in awe by the view before our eyes but later when we look at the pictures… things are far from picture-perfect. The perfect automated mechanism of the camera levelled out brightness and contrast and the photograph turned out sterile – the giant flaming sun is now white and not red, the thin shafts of light seeping through the branches are invisible and the mood we felt while shooting has all but vanished. In such situations we need to able to intervene with the work of the camera and make some adjustments while shooting. The most frequent adjustments will certainly have to do with the camera exposure. Some models offer simple adjustment options at the touch of a single button within certain narrow boundaries while others offer full manual adjustment of all parameters. The main camera settings we can use to correct the image have not changed since the dawn of photography 200 years ago. Photography means ‘painting with light’ and it is only logical to assume that these settings will be related to the amount of light which falls onto the light-sensitive material within the camera (film or sensor). If there is extra light, the photo will be too light (overexposed) and if it is too little, it will be too dark (underexposed).
We will look at the main parameters which we can use to control light.
- The light-gathering capacity of the lens (in the German and Bulgarian photography jargon the term is ‘blende’). In English-speaking countries the term is ‘Aperture’ – f stop. The lens is one of the most important components in the camera. The lens is responsible for objectively projecting reality onto the light-sensitive material of the camera. Different lenses have different capacity to let the surrounding light in. Naturally, this capacity depends on the quality of the optical lenses being used, but in modern lenses the light-gathering capacity is determined by two main factors – maximum entrance pupil (diaphragm opening diameter) and focal length of the lens. The bigger the opening, the more light the lens lets in, similarly to how a large window lets more light into a room compared to a small one. We can therefore say that the light-gathering power of a lens is directly proportional to the diameter of the maximum opening. What will happen if we move away from the window? Because light is ultra high-frequency electromagnetic radiation, it follows some well-known laws of physics – doubling the distance leads to a fourfold drop in intensity. That means that the further away we are from the window, the poorer the illumination will be. When it comes to lenses, this distance is measured from the main optical surface to the point of projection and it is called ‘focal length’.
Probably we have all had the experience of playing with a magnifying glass as children, trying to burn a hole through a piece of paper by focusing sunlight. There is one specific position of the lens which causes a small bright dot to appear on the sheet of paper – this is the projection of the sun. A magnifying glass is a simple lens similar to a monocle and if you measure the distance between the magnifying glass and the projection of the sun, you will find the exact focal length of this lens. And so – the greater the focal length of the lens, the lower its light power, which is inversely proportional to focal length. To put it simply, the light power (aperture) is the ratio between the maximum diaphragm opening and the focal length of the lens. If you have a lens with a 50mm maximum opening and focal length of 100mm, its light gathering power will be 50/100 or 1:2 . For such a lens we say that it has aperture f/2. If a 50mm maximum opening corresponds to focal length of 200mm, its respective light-gathering power will be 1:4 or aperture f/4. A lens with aperture f/2 lets in 4 times more light than one with aperture f/4. Often beginners find it hard to understand why a higher aperture value means less light. Why a lens with aperture 4 lets in less light that one with aperture 2. The explanation is simple – these are denominators.in a fraction. 1:2 is a greater number than 1:4 the same way half a pizza is more than a quarter.
Inside the tubus of the lens there is a special diaphragm made from metal blades which can be used to alter the diameter of the entrance pupil and adjust the amount of light which is let in. Thus, if the focal length of the lens is a constant, we change its light power (aperture – f stop). If there is strong ambient light we can limit it by closing the diaphragm (bright sun on the beach or a combination of sun and snow in the mountains), or if the light is too little, we can open the diaphragm to let in as much as possible (cloudy gloomy weather, deep shade, etc.). Attention! Lenses with greater light power (aperture below f/2) are more valuable because they allow us to shoot under poor light conditions.
As you might have already guessed, this parameter is not the only one. Well, you guessed right! These symbols were only applicable for fixed exposure times of 1/100 sec and 100 ISO. And so we made it to the second parameter.
- Exposure time (shutter speed)
In eighth grade students are often required to solve math problems where a pool is slowly being filled by means of one or more pipes over a certain period of time. In fact, if the pipe is only one, the amount of water in the pool will depend on the diameter of the pipe and filling times (provided that pressure is constant). The photographic sensor gets ‘filled’ with light following an identical principle. In addition to the light-gathering power of the lens, it is important to take into consideration the period of time over which it is exposed to the radiation of a stream of photons. The longer the period of time, the more photons reach the light sensitive sensor. This process is called ‘exposure time’ and is controlled by a precise mechanism, called a shutter. A shutter is usually an opaque blind made from hard metal leafs which allow light to pass through only for a pre-set specific amount of time. If time is too short, our ‘pool’ will not be filled in, and if time is longer, it will overflow. In photography jargon, exposure time is often called ‘shutter speed’. In English you can also hear it called ‘time value’ – Tv or ‘shutter speed’ – S. Shutter speed and aperture are connected like communicating vessels. The more open the aperture is, the more light is let in, and thus – faster shutter speed and vice versa..
In the chapters dedicated to motion we will analyse in detail the importance of exposure time in capturing motion, but it is worth noting at this point that at longer exposure times moving objects travel a certain distance and their projection onto a single frame will be a blurred image. If we want to freeze a moment and get a sharp image, we need to use shorter exposure times (higher shutter speeds). The graph below gives you a visual representation of this relation:
Keep in mind that at low shutter speeds even a still object can be blurred because of a slight shake of your hand. Follow this simple rule: shutter speed should be one over the millimetres of the lens – for a 100mm lens – 1/100 sec, for a 50mm lens – 1/50 sec. Naturally, it all depends on how stable your hand is, but it is still a useful guideline.
- Sensitivity (ISO)
This is the third important parameter which determines correct image exposure. It is directly related to the other two. If the sensitivity to light is low, this means that exposure time should be longer. As we have already said, this was a major issue when photography was in its infancy. Emulsion sensitivity was so low that exposure had to last for hours. At the time there was no need for a shutter and ‘shutter speed’ as a term did not exist. Time was measured using a clock or a watch and the cap of the lens acted as a barrier to light. The development of the shutter is closely linked to the increase in sensitivity and the need to freeze the moment in time with exposure times shorter than a second. There is no way, however, you could measure 1/100 sec using a clock nor do human reflexes allow for the reaction times needed to take the lens cap off and then put it back on within such short time frames. The first mechanical shutters able to measure fractions of the second were designed by well-established companies producing clocks.
Sensitivity is also related to the amount of light which is let through the lens and controlled with the help of the aperture. Higher sensitivity requires less light and vice versa – when sensitivity is low, we need to use maximum aperture and/or reduce shutter speed. Over the years there have been several sensitivity standards. Well-known standards are the Russian standard ГОСТ, the German standard DIN and the American standard ASA. The universal standard ISO was established at the end of the 20th century. The biggest advantage of digital cameras is that the sensitivity of the sensor can be changed within certain limits by increasing the strength of the signal. Sensitivities with practical application in film photography include between 50 and 800ISO, rarely reaching up to 1600 or 3200, though at the expense of quality. For digital amateur class compact cameras and smart phones very good results can be achieved with sensitivity at 50-400 ISO, 800 ISO is a compromise while at 1600 ISO noise levels are so high that the image is usually unprintable. Producers usually resort to aggressive noise reduction algorithms. The effect of their application is considerable reduction of visible noise, although always at the expense of less detail and new additional artefacts. In the case of modern cameras with a large sensor practically usable sensitivities are within the 100-6400 ISO range, sometimes reaching as high as 12800 ISO. This is only possible due to the larger size of the sensor and the larger area with light sensitive photocells.
In the example below you can see a full-sized photo followed by 100% crops at sensitivity of 800, 6400 and 25600 ISO, respectively. High sensitivity makes the image look coarser and leads to high levels of noise.
When it comes to low-range compact cameras and smart phones, which are used by beginner amateurs who copy their images without any further edit, the use of noise reduction software may be justified, but when it comes to expensive models within the high price range, you should be able to turn this option off using the menu. It is always better to have an image with high resolution, even at the expense of more noise, because noise can be removed more successfully with the help of a special software programme later and not with the inbuilt software in the camera. We can also do this when shooting in RAW format. Unfortunately most amateur class cameras do not support RAW format. Another reason for the differences in noise levels observed even with camera noise reduction turned off and after edit in the RAW converter of Photoshop, is the rather frivolous interpretation of the term ISO some producers have. At equal signal amplification levels and identical sensors, noise should also be the same. Unfortunately, alleged sensitivity of 100 ISO of one model corresponds to 160 or 80 ISO in other models. This has largely contributed to some misunderstanding concerning noise. The truth is that we should not look at the ISO value given by the producer, but at the exact rate of signal amplification.
In the graph below you can see a number of sensitivity values. Do not forget the increasing sensitivity leads to a corresponding decrease in image quality – noise levels go up and resolution goes down.
As we said earlier, sensitivity is closely related to aperture and shutter speed. Let us assume that at settings of 100 ISO we have aperture 4 and shutter speed of 1/50 sec but we would like to shoot a moving object. 1/50 sec will be insufficient and the moving object will be blurred. In this case we can increase shutter speed (decrease exposure time) 4 times to not more than 1/200 sec. We can do this by opening aperture to 2 and letting in 4 times more light, but if our lens cannot support this option, we can raise sensitivity four times from 100 to 400 ISO. If we want to freeze the motion even more effectively, we can shoot at 1/500 sec or 10 times higher shutter speed. In this case, if we want to have correct image exposure, ISO should be set at 1000.
So, now that we have discussed what aperture, shutter speed and sensitivity mean, let us take a look at how these settings can be adjusted on our cameras.
The upper part of any modern digital camera with an option for manual settings features a round selector dial with some basic symbols.
- A green/red square or an Auto sign – the camera automatically chooses speed, aperture and sensitivity and you only press the shutter.
- ‘P’ symbol – Programme mode. The camera automatically chooses speed and aperture, but you can adjust sensitivity (ISO) and make general exposure adjustments with the use of the additional +/- symbol; by pressing on + you let in more light (using a combination of opening aperture and reducing speed), and by pressing on – you let in less light and the image becomes darker.
- ‘A’ or ‘Av’ symbol Aperture Priority mode – you select he aperture and ISO, the camera selects the speed. Often used in portrait, landscape, and interior photography for better control over the depth of sharp focus or depth of field (DOF). Aperture, in addition to being a tool to control the amount of incoming light, can be used as a tool to regulate the depth of field /DOF/ or the ratio between focus and defocus areas in the image. The more open the aperture (more open apertures have lower numbers), the more defocus in the background.
- ‘S’ or ‘Tv’ symbol. Speed Priority mode. We select the speed, and the camera selects the aperture and ISO (unless selected in advance). This mode is often used when taking photos of moving objects in order to freeze the motion or to achieve a blurred motion effect.
- ‘M’ symbol. Manual mode. You select speed, aperture and ISO settings manually. This mode is especially suitable for work under controlled steady light, such as in a studio. By setting in advance all parameters correctly, you take images with the same exposure.
We will discuss all these settings further in the other chapters of the book and we will describe them in detail below many of the photographs.