Читать книгу Digital Photographer - Литагент HarperCollins USD, J. F. C. Harrison, Professor J. D. Scoffbowl - Страница 5
ОглавлениеEverybody takes pictures – and virtually everyone now shoots digitally. The medium offers many advantages, and it is easy to see why digital has replaced film. You can view your pictures immediately, and digital images are incredibly accessible when you transfer them from the camera. But let’s start with the basics: what do you need to begin taking great images?
Digital compact cameras are small, portable and inexpensive. They are easy to use for beginners as well as being ideal ‘go anywhere’ cameras for more experienced photographers.
Megapixel Ratings
The ‘megapixel’ rating typically found on digital compacts is a rough guide to the picture quality you can expect, although this is not as important now as it was when digital imaging technology was first emerging. This is because these days digital photography has advanced so much that just about any camera will take a reasonable image, regardless of the number of megapixels that it advertises. Five megapixels will give you excellent 6” x 4” prints and good enlargements up to 7” x 5” or even 10” x 8”. If you regularly want to print at larger sizes, go for a higher-resolution camera with 7—10 megapixels.
Zoom Ranges
How long a zoom range do you want? Basic digital cameras usually have a ‘3x’ zoom range. In other words, this means that at the maximum telephoto setting you get a 3x magnification compared to the wide-angle setting. If you want to shoot subjects which are further away, you need a longer zoom range. Some compact cameras have zoom ranges up to 6x, but if you want more (10x or 12x), you should look for a ‘superzoom’ camera, though these are generally bulkier.
SMALL, HANDY DIGITAL COMPACT CAMERAS ARE IDEAL FOR CAPTURING IMPROMPTU MOMENTS AND EVERYDAY EVENTS.
LCDs The LCDs (liquid crystal displays) on all digital cameras - from mobile phones to high quality SLRs - offer the advantage of instant display of your image, the moment it has been taken.
Tips for Basic Usage
Most compact digital cameras are designed for simple snapshot operation, and control the shutter speed and aperture automatically. If you want to control these manually, you will need to look for cameras with ‘PASM’ (Program AE, Aperture-priority, Shutter-priority and Manual) modes.
Check the battery life of your compact. Some cameras may take as few as 100–150 shots on a single charge, which is not always enough for a full day’s shooting. Aim for a battery life of 200 shots or more.
Here are a couple of tips you can use in order to take better shots. Firstly, use the LCD to compose shots when you can, rather than the camera’s optical viewfinder. Optical viewfinders are good in bright light, when the LCD can become hard to see, but they do not give an accurate indication of the precise area that the camera will photograph.
You will also notice that compact digital cameras suffer from ‘shutter lag’, in which case you press the shutter release, but the shutter does not fire straight away. This can make it difficult to time your shots accurately. To get around the problem, line up your shot first and then half-press the shutter button. The camera will focus and the focus will remain ‘locked’ while the button remains half-pressed. Now wait for exactly the right moment to take the shot, then press the button the rest of the way until it is fully depressed. The shot will be taken instantly, without any shutter lag.
HANDY CAMS Digital compact cameras come in a variety of shapes and sizes. Choose one that will fit in a pocket or handbag and you will have it readily to hand whenever you want to take a picture.
Digital compact cameras are great for taking fun snaps with friends and showing them off to anyone who is interested. If the image does not come out well, simply delete it and take it again. If you are happy with the results in the LCD, you have your image.
HANDLING AN SLR Digital SLRs are much bigger and heavier than digital compact cameras, which means you cannot just slip one into a pocket or a handbag – you need to make a conscious, deliberate decision to carry one around with you, especially if you want to have the option of using more than one lens, or fitting an external flashgun. In that case, you will need to pack everything into a bag. Unless you have extremely small hands you will find that SLRs – despite their size and weight – handle extremely well, with their chunky handgrips.
While digital compacts are fine for snapshots, a digital SLR is required if you want to create more advanced images such as this stunning still-life study.
What is an ‘SLR’?
The acronym SLR stands for ‘Single Lens Reflex’. When you use an SLR, the picture is composed and taken through the camera’s single lens. ‘Reflex’ refers to the mirror which is used to reflect the image up into the viewfinder until the moment the shutter is released. The mirror flips up and the image then passes to the sensor at the back of the camera.
Low-cost digital SLRs have 6—10 megapixel sensors which can yield very good results, but it is worth paying a little extra for a camera with more pixels. The difference in fine detail is visible.
Lenses, Kits and Accessories
You can use different lenses on a digital SLR and manufacturers sell them in ‘body-only’ form, in which case you have to buy a lens separately, or as a camera ‘kit’, when a generalpurpose zoom lens is included. If you already own compatible lenses, it might make sense to buy the body on its own. However, if this is your first digital SLR, you should get a kit with a lens included. This will be much cheaper than buying the body and the lens separately.
Single-Lens Reflex (SLR) cameras are technologically advanced pieces of equipment capable, with the right lens or accessory, of taking virtually any picture you could imagine.
The Benefits of SLRs
Digital SLRs are as easy to use as compact digital cameras. All have ‘point-and-shoot’ fully automatic modes, so beginners can explore the more advanced options at their own pace. Having said that, it may be necessary to modify your shooting technique a little if you are used to a compact digital camera. This is because digital SLRs have much less depth-of-field (near-to-far sharpness) than compacts, so when you graduate to an SLR you will need to get to grips with lens apertures and how these affect depth-of-field. SLRs also have faster focusing systems than compacts, so there is less risk of shutter lag.
Finally, because the pictures are sharper than those from compacts (and digital SLR users will be expecting more from their photos anyway), it is a good idea to invest in a tripod to help avoid camera-shake in low light and to aid careful composition whenever time and space permit.
YOU CAN TAKE GREAT IMAGES ON AN AFFORDABLE DIGITAL SLR WHICH CAN BE BLOWN UP TO A3 AND BEYOND.
Many photographers want a wider zooming range or more photographic control than an ordinary compact digital camera can provide, yet they do not want the size and weight of a digital SLR.
Alternative Cameras
A ‘bridge’ camera may be the answer. These offer many of the advanced controls of digital SLRs but in a smaller and less expensive body with a fixed lens. This lens may offer a very wide zoom range, perfect for photographers who want a single, ‘all-in-one’ camera.
Camera phones are becoming more popular, but the picture quality is still not of the standard you would expect from even a basic digital camera. Another alternative is to use a camcorder – most will take stills as well as video footage —but again, image quality can be an issue.
OTHER MEDIA Most images from a camcorder are only 1–2Mb or so in size, which means that the quality is a long way short of what you get from a digital camera.
Images taken with a mobile phone look fine when reproduced reasonably small, but as soon as you enlarge them they appear ‘soft’ and lacking in sharpness.
Single lens reflex cameras enable you to change lenses to achieve a variety of effects. The camera’s standard lens will give an angle of view roughly similar to that we perceive with the naked eye, a wide-angle lens enables you to get more into the frame, while a telephoto magnifies distant objects.
Lens Properties
There are other lens properties to take into account, apart from their focal length, including the maximum aperture. The larger the maximum aperture, the more light the lens can gather. This is useful in poor light or whenever you want shallow depth-of-field in your photographs.
Zoom Lenses
In modern cameras, zoom lenses have largely taken over from lenses with fixed focal lengths (’prime’ lenses). The versatility of zooms means that you do not have to carry around a number of different prime lenses, or keep changing lenses for different subjects. However, zoom lenses do have a couple of intrinsic disadvantages. One is that their maximum apertures are lower than those of prime lenses. Whereas a 50mm prime lens might have a maximum aperture of f/1.8, a typical ‘standard zoom’ might have a maximum aperture of f/4 at this focal length.
If you want to make much impact on subjects such as birds and motorsport, you will need a super-telephoto lens like this Sigma 800mm f/5.6.
Lens Mounts
Each digital SLR brand uses a different lens mount. A Nikon lens, for example, will not fit a Canon camera. However, you do not have to buy lenses made by your camera’s maker. Independent companies such as Sigma, for example, make lenses which can be supplied in different mounts according to the brand of camera you are using. These lenses are just as serviceable as those supplied by leading camera firms.
Independent Lenses Versus Marque Lenses
Lenses made by independent companies are generally much cheaper than those offered by the camera maker. The optical performance is often very good and it may be difficult to see the difference in image quality between photographs taken using a good-quality independent lens and those taken on a more expensive ‘marque’ lens. Having said that, when you buy a lens you are not just paying for image quality. Marque lenses may be better made than those from independent companies and are consequently more likely to withstand years of hard use. Their design and finish will be consistent with other lenses in the same range, and with the camera bodies which they are designed to accompany, and the lens range may include more sophisticated and specialized lenses that you cannot get elsewhere.
Of course these lenses can be used indoors as well - whenever you need an adaptable focal length.
EQUIVALENT FOCAL LENGTH Photographers using 35mm cameras are used to judging the angle of view of a lens by its focal length. However, with a couple of exceptions, digital SLRs have physically smaller sensors, so that the angle of view of the lens is reduced and it appears to have a longer focal length. You need to multiply the actual focal length by a factor of 1.5 or 1.6 to get its ‘effective’ focal length. For example, on a digital SLR a 50mm lens effectively becomes an 80mm lens.
As the focal length of a lens increases, so its angle-of-view narrows. Wide-angle lenses take in lots of the scene because they have a large angle-of-view. With super-telephoto lenses the angle is reduced to just a few degrees, and little of the scene is included.
