Walk around many large cities these days and you’ll see people walking around with cameras. No longer just tourists recording holiday snaps for posterity, the accessibility of digital photography was led to residents grabbing their camera and digitizing the scenes they see every day. Photography has a long history and while it is possible to get fantastic shots with just a cheap compact, going any further confronts the amateur with a pile of jargon. Understanding some of this can bring out the full power of your camera.

Types of Camera

Digital Cameras come in all shapes and sizes. Prices can range from less than £100 to many thousand pounds.

• Camera Phones - Almost all mobile phones now come with cameras. The phone networks love them because they can get massive fees from people sending photos of themselves on nights out or videos of them dancing to the latest songs from Glee. While it is common now for these cameras to have multi-megapixel sensors, the actual hardware is normally fairly cheap. The lenses are small and so are the sensors and they generally lack the features of dedicated cameras. They are however really handy keeping with you for use whenever you need them.
• Compact Cameras - These are most people’s way in to photography, being cheaper than larger cameras. Manufactures are constantly finding more and more features to simplify the photography process which they include on compacts. Many are aimed at the causal user, so have an easy learning curve and features such as face and smile recognition to make sure people get the best results possible. While perfect for point and shoot photography, some often hide more powerful features for advanced users. Most compacts will also record movie clips. Compacts are have their disadvantages too, they often take some time to power up and there can be a delay between pressing the shutter button and the picture being taken. The lenses are smaller and so are the sensors, so they can never produce images of as high quality as larger SLRs.
• Bridge Cameras - Are also known as Superzooms. These are larger compacts with big lenses and large zoom ranges (between 10 and 20 times zoom). They often include the kind of manual controls that one would expect from an SLR. Bridge cameras often can record HD video. They don’t have the large sensors of SLRs but they provide a lot of versatility for the money, as they normally cost a lot less than a big zoom lenses for an SLR.
• Digital SLRs - The Single Lens Reflex camera has long been the standard for most non-studio photographers. In the days of film, their manual controls and interchangeable lenses made them versatile and powerful. The DSLR likewise is pretty much the king of the hill. The light that comes through the lens is reflected up to the viewfinder, with the mirror flicking away when the actual photograph is taken. DSLRs have much larger sensors than compact cameras, this means they have better image quality and also can work better in low light situations. As well as this, they use much better lenses that allow more light in. They power up and record images almost instantly. Normally they have a mass of manual controls and the ability to simply point and shoot, catering for all users. Some of the cheaper DSLRs don’t have Liveview¹ on the LCD screen as the image sensor only gets images when the mirror is up, More expensive DSLRs have a separate sensor for the Liveview. Not all DSLRs record video, but those that do can produce outstanding results thanks to lenses and sensors that rival professional video cameras but at a fraction of the cost. Lenses only tend to work with one make of camera, once you have decided on a make for your first DSLR, you are most likely to upgrade to a more professional model so that you can use all your old lenses. Dust is a problem for DSLRs, as it can get onto the sensor when changing lenses. Many cameras can clean their own sensor.
• Four Thirds - Are like SLRs but using a smaller sensor and enclosed in a smaller body. They use their own interchangeable lenses. They often have similar features to SLRs of the same price and can normally produce video.
• Medium Format - Medium Format cameras, like their old film counterparts, are rarely seen outside the studio. They have large sensors, high resolution and lost a lot of money. Some film Medium Format cameras can be fitted with a high resolution digital back.

Megapixels and Sensors

Megapixels are the headline figure for all digital cameras. But is it just as simple as the more megapixels, the better?

Images are recorded on sensors. Each dot is recorded on a pixel. Therefore a one megapixel sensor can record an image with one million dots. Surely the more dots, the better?

Not so. More megapixels do not mean larger sensors. The larger the sensor, the more light can fall on it and the better the single to noise ratio. A 10MP DSLR will tend to produce better images than a 15MP compact camera. Large sensors work much better in low light conditions.

A full frame DSLR sensor is the same size as frame of 35mm film. It has an area of 864mm2. Most cheap DSLRs use ‘APS-C’ or DX sized sensors, of between 320 to 390mm2. The most common size for a compact camera is 25mm2, far smaller than a DSLR.

Since DSLR cameras take their dimensions from 35mm film; they have an aspect ratio² of 3:2. Compacts tend to be designed for displaying their images on computers, so have a 4:3 ratio.

Exposing Yourself

When you press the shutter release button, you expose the sensor to light. Back in the film days, each photo was an exposure. Normally the camera will work out what settings to use for each photo, but you can do this manually. An overexposed photo means that all the details in the highlights³ are lost or ‘blown out’. This often occurs when you take a photo of a person or building and the camera works out how to best get the details from them, and ignores the sky, which since it is brighter than the building or person, loses most of its detail. A underexposed photo is where details are lost in the shadows. This can often be because the camera takes its settings from the sky instead of the subject. It can also be if there is not enough light in the room.

Digital sensors are far more sensitive to over and under exposure than film used to be. Blown out highlights can be extremely tricky, if not impossible, to fix using a computer afterwards. Detail lost in the shadows are difficult to bring out without bring out lots of digital noise. The best way of getting the most detail is to make sure the photo is correctly exposed when you take it. A useful tool is the histogram, a graph that many cameras show. It shows the amount of pixels at each brightness level, with black on the left and white on the right. Since true white and true black do not occur in the real world, if the histogram shows pixels at either end, then the image is not perfectly exposed.

There are four factors that affect the exposure: ISO sensitivity, shutter speed and shutter aperture and light level. Unless you are using a flash or external lighting, you have little control over the light level.

ISO

Again we have to go back to the days of film. Films came in different sensitivity for different uses, the ASA scale. Digital cameras use the same system for their light sensitivity, where it is known as ISO. ISO 50 to 100 is useful in bright conditions, 400 for dull conditions or when there is a lot of action in the scene. DSLRs can have ISOs well above 1600. There is a trade-off for this extra sensitivity, the higher the ISO, the grainer the picture and the more noise in it.

Aperture

This is where things get a teeny bit complicated, as we first hear the dreaded term: f-stop. The f number is basically the size of the aperture in the lens. The largest apertures are f/1 and f/1.4 going down to f/128 and below. The larger the aperture, the more light that comes into the camera, which means the ISO can be less sensitive or the shutter speed can be quicker. Each f-stop lets in half the amount of light as the previous one in the sequence. A typical lens will start from f/4 or f/5.6. High end lenses may start at f/1.4, these are often called fast lenses.

There is a second effect of changing the aperture size, this is that the depth of field changes. The depth of field is how much of the picture is in focus. At large apertures, the depth of field is very small, so only a small amount of the picture is in focus. Portrait and sports photographers use this to make the subject pin-sharp but blur all the background details. A small aperture leads to a large depth of field with lots of objects in focus.

Depth of field also varies depending on the distance between the lens and the sensor. Camera phones and compact cameras have a massive depth of field, meaning most things are in focus. A DSLR normally has a smaller depth of field, meaning that getting the focus correct is vitally important.

Shutter Speed

This is simpler, the faster the shutter opens and closes, the less light comes in. A quick exposure means that action is frozen and the camera is less likely to be affected by hands shaking. Longer exposures can have more action in them, or are more useful in low light conditions. Depending on the photographer and the level of zoom, anything around 1/15s or slower is at risk of blur though shaky hands. Many advanced cameras have a Bulb or B mode, this keeps the shutter open as long as the button is pressed.

A simple rule for shutter speed on a sunny day is that using an f/16 aperture, then the exposure speed should be the reciprocal of the ISO. So for ISO 100 sensitivity, the shutter should be open for 1/100s. This is the sunny 16ths rule.

Lenses and Zooms

When talking about lenses and zooms, you will often hear the term focal length. What it really means does not matter for now, but it is a term used to describe how much magnification the lens produces.

There are a few other terms we need to get quickly out of the way:

• Wide Angle - is where the angle of view is wider than we would see normally. Two effects of these lenses are that perspective effects are increased and so is the depth of field.
• Telephoto - is the correct term for a lens with high magnification. Perspective effects are reduced, likewise the depth of field. This means that focusing has to be accurate.
• Zoom - is the process of having a variable focal length, this allows you to get different magnifications on your photos.
• Digital Zoom - was popular in early digital cameras. This basically cut away the outside of the image and produced a picture just consisting of the middle. Now that image editing software is readily available, and most compact cameras come with optical zoon, digital zoom is pretty much pointless.
• Optical Zoom - is when a lens has variable focal lengths. Most compacts and bridge cameras have optical zooms, and many lenses for DSLRs are zoom lenses.
• Prime Lens - is a lens for a DSLR that has a fixed focal length, and normally a wide to medium angle of view. These often are cheaper and lighter than zoom lenses and are much easier to make with large apertures, so are great for fast shutter speeds.

Again, focal lengths hark back to the days of 35mm film. A focal length of around 50mm is a normal lens. Going below to 35mm you come to the wide angle zone, with ultra-wide angle lenses coming in below 18mm. Above 70mm or so, you get to the short telephoto lenses. 200mm is a reasonable telephoto lens. Bridge cameras and some long DLSR lenses come in at 500mm and above!

Compact and bridge cameras will often be advertised as having something like a 10 times zoom. This means that the longest focal length is ten times the length of the shortest. A buyer should check out what he actual focal lengths are because a 10 times zoom on a lens starting from 35mm will have better magnification than a 12 times starting at 28mm.

Focal lengths are all based on the size of the sensor being the same as a frame of 35mm film. Bridges and compacts, which have smaller sensors, focal lengths given as 35mm equivalents. DSLR cameras with DX sensors don’t get the full image from their lenses, which are normally designed for full frame cameras. In order to work out the equivalent angle of view, you need to multiply the focal length by 1.5 or 1.6 depending on the make of the camera.

Zoom lenses loose more light in them than fixed lenses. Telephotos also need more light. A long zoom lens that can be used at f/2.8 can cost many thousands of pounds.

For most DSLR users, the lenses are the really expensive part of photography. A new lens can easily cost as much as a new camera. Most makes have different screw fits, so lenses are not interchangeable between, for instance, Canon and Nikon.

Flash

The flash gun is a device that momentarily emits a very bright light. These are useful for lighting up subjects in the dark or for freezing a moving object. Most cameras have some form of on board flash gun, and many cameras are more than eager, even in bright lighting, to trigger their auto-flash. Flash guns are not a universal save-all, and many times actually have little effect.

A useful effect is the fill-flash, this is when you have a dark subject in front of a bright background, such as a window. The fill-flash mode means that the camera exposes for the background and fires the flash so that the subject is also properly exposed.

Another effect is curtaining. This is when the exposure is quite long, so that you get the detail of the subject and then motion trails leading from them.

Flash guns only have a limited range. A good onboard flash gun has a range of 10 meters or so. Despite this, you can see onboard flashes going off any many football matches or concerts. That the photos come out is purely do to the lighting on stage or on the pitch, all the flash gun is actually doing its illuminating the heads and backs of the people in the few rows in front of you.

On board flashes have the problem of red-eye. This is when the light bounces off the blood vessels in the inside of the eye, often in low light conditions. It is caused when the flash is close to the lens and when the pupil is wide open. Red eye reduction flashes fire pre-bursts of light to reduce the pupil size but they delay the actual shot so that if you may miss the moment you are trying to capture.

Pop up flashes reduce this effect a bit as it is further from the lens, and external flash guns reduce it even more. External flash guns with a tiltable head allow you to bounce the flash from a reflective surface like a ceiling or an umbrella. Not only does this stop red-eye, it reduces the very harsh shadows that flash guns produce. External flash guns can be remotely triggered so that you can hold them at a different angle than the camera, which can produce very interesting results.

DSLR and bridge cameras, as well as some compacts have a connector for the flash gun on the top, called a hotshoe. If you have an old flash gun from your film camera, you may be tempted to use it, do not. While in the film days, flash guns worked across all cameras, the modern breed of digital camera makers design their cameras to work with only specific flash guns. Using the wrong gun, even if it does fit onto the hotshoe, can result in all the electronics in your camera being fried!

Image Stabilisation

It is a fact that it is impossible to hold a camera perfectly still. With high shutter speeds this isn’t a problem, but at longer exposures, the shake can become apparent. Shake is also more noticeable at longer focal lengths. A rule of thumb is that the shutter speed shake to be noticeable is the reciprocal of the focal length, so a 200mm lens shake will be noticeable at 1/200th of a second.

A simple solution is placing your camera on something like a table, a wall or a tripod. This is the only real solution for long exposures.

For exposures around the point when shake becomes noticeable, the camera makers have introduced image stabilisation. Image stabilisers allow exposures to be 4 to 16 times longer. This can be done by either moving the sensor or the lens elements in response to minute movements. Many compact and bridge cameras have image stabilisers. In DSLR, things get a bit more complicated. When you only have one lens, as in compacts, it doesn’t matter if the stabilisation is lens based or sensor based, but it does matter with DSLRs. Some companies use lens based and some use sensor based stabilisation.

Lens based stabilisation is better in terms of effect. It allows longer exposures than sensor based, but in order for it to work; each lens has to have the technology, meaning that the lenses have to be more expensive. If you use non stabilised lenses, you can’t get any stabilisation.

Sensor based stabilisation means that the technology is built into the camera body so works with any lens you fit, but not as effectively. Also, it doesn’t work with video.

Filters

Some compact and bridge cameras can be fitted with filters, as can all DSLRs. A filter is a transparent piece of plastic that alters the image coming into the camera. Some, like coloured filters are not as popular as they were in film days as their effect can be synthesized on the computer afterwards. These are some other common filters.

• UV filter - Most cameras have an onboard filter to removes UV light, so they have little actual effect, but they have a more important use. Since they are cheap and do nothing to effect the image, they are often fitted onto the front of a lens to protect it from scratches. If the UV filter gets damaged, it is easy to replace. If a lens gets a scratch, it is little more than a £1000 paperweight.
• Circular Polariser - These are polarised filters that reduce glare from reflective surfaces like glass, produce more contrast in the sky and increase the strength of the colours in the image.
• Neutral Density Filter - This blocks all colours of light equally. These are used to either increase the time the shutter has to be open or the size of the aperture. They are commonly used when photographing running water on a bright day, it allows you to use a longer exposure to make the water look silky.
• Graduated ND filter - This is basically an ND filter over half the filter and clear over the other half. These are great for photographing the outdoor scenes, they allow the photo to be exposed for the ground and the highlights not being blown out in the bright sky.

Scenes and Modes

Most cameras have a number of modes for different situations. Most will have an auto mode that is useful most situations. Various scene modes will alter various internal processing, and will activate or cancel other features such as the flash or face recognition.

Cameras aimed at more advanced users will have P, S, A and M modes. P mode stands for Program Mode, this is where the camera automatically sets the aperture and shutter speed and lets you set everything else. S stands for Shutter Priority, and lets you set the shutter speed and the camera will judge what aperture it needs to use. This mode is useful for setting up long exposures. A stands for Aperture Priority and lets you set the aperture you want to use. This is useful if you want to blur out backgrounds. M is a manual mode, where you can adjust all the settings.

Storing Images

Cameras store their images on memory cards. Normally these have capacities of a gigabyte or more. There are a few different types of card, and have been around long enough for them to be fairly cheap. In practical terms there is little difference between using different types of cards.

Image formats

Cameras store images in a number of formats. The three most common are RAW, TIFF and JPEG.

RAW is the most basic form of storage where all the image data is stored in one big file. These are great if you are using a program like Photoshop to edit your pictures as no image data is lost and things like white balance can be altered by RAW importing software. On the downside, they are large files and operating systems like Windows can’t view them in the folder views. Most camera makers use their own version of RAWs so they normally have to be converted into either a universal (Adobe) format or JPEG to be edited.

TIFF is an old image format that is still used in the publishing and printing world. It is universally recognised by all major software packages (although Windows Explorer still won’t let you view the images) and loses no image data when saved. However they don’t have the versatility of RAWs or the small size of JPEG, so unless you are sending images straight to a printer, they offer no real benefits over the other types.

JPEG is a way of compressing images into smaller files. It uses some complicated mathematics and advanced guesswork to reduce image size without overly affecting the quality of the image. All JPEGs lose some picture quality, and the more you compress, the poorer quality the image. JPEG format allows you to store more images and write them to the card faster but they lose some of the quality and versatility of RAW files. Windows Explorer can view JPEG files and can display them as slideshows. JPEG is a useful way of storing images, especially for simple snapshots and exporting to the Internet.