Digital Camera Master

To get the most from your digital photographs, you need a computer in order to store and display your images, to print them, turn them into web pages, run slideshows, email them and edit them.

The great thing about computer systems is that you can expand them as you go along, adding the devices and internal components you need. But while upgrading your printer, scanner and digital camera won’t be a problem, improving other aspects of your PC’s performance might be.

In particular, if your PC is more than a couple of years old, it’s likely to have a pretty slow processor - by today’s standards, anyway. It’s possible to limp along with an old 500MHz Pentium III, but in order to work with today’s high-resolution images you really need something a lot faster. An entry-level 1GHz machine will be fine for nearly every purpose, but if you can stretch to it, a 2GHz PC will really race along, and you shouldn’t have to think about upgrading again for quite a few years to come.

Our annotated diagram on the previous page will show you what else you need to look out for when you’re planning your perfect digital photography system.

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The Nikon CoolPix series has a set of screw-on lenses, including a wide-angle (0.66x) converter. This turns a standard lens at its widest setting, equivalent to 35mm, into a 24mm lens. It’s surprisingly cheap at well under a £100. Sounds great, but there are problems with barrel distortion and chromatic aberration at the edges. It simply isn’t possible with a cheap screw-on lens of this type to achieve the quality of a 35mm SLR lens.

At smaller sizes, or on web pages, you won’t notice the lack of quality, and the lens is small and easy to carry round. If you want to preserve image quality, it may well be better to move further back. We have been known to get our feet wet in a canal.

If you want to include the whole of the building and use your camera’s built-in lens at its best, then that’s the only easy option.

Or you can take a panorama. Holding the camera vertically, take a series of overlapping shots. Then simply stitch them together in an image editor like Elements or Paint Shop Pro

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It sounds like you may have resampled the photograph down to a small size rather than changed the display size. Here we are dealing with the thorny subject of resolution and print size - one of the most misunderstood concepts in digital photography.

When measuring the size of digital photographs, there really is only one sort of measurement that’s important, and that is the pixel dimensions. A digital photograph is a certain number of pixels wide and high. Many digital cameras produce pictures at 1,600 x 1,200 pixels. The size you display the image is up to you. If you’re making a digital print, then 200 pixels per inch will give you good results.

This resolution gives a print size of 8 x 6 inches. A problem lurks on screen when preparing the image for printing because most digital cameras produce images that have a default setting of 72 pixels per inch (ppi), which is the resolution of the average computer monitor.

At this resolution, our picture will fill the entire screen area of a large size 1,600 x 1,200 pixel monitor, which is approximately 22 x 16 inches - far too big to fit inside the dimensions of an 8 x 6 print.

We need to change the picture dimension settings and shrink the display size down from large screen size to small print size, and this is where many people go wrong - they reduce the display size but keep the resolution at 72ppi.

The computer, being the dumb machine that it is, will then resample the image from 1,600 x 1,200 pixels (5.5- megabytes) down to 576 x 432 (just under three quarters of a megabyte) throwing away over 85 per cent of the picture information

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Auto-exposure is a marvel of camera technology, the result of years of development work by talented R&D teams. But there are times when we’d rather dump the auto-exposure technology and use manual settings. This may be under unusual lighting conditions or for creative work - roughly 20 per cent of the time for many users.

The more expensive cameras have manual over-ride, but if your camera doesn’t have this facility, it is still possible to exert your control and get the camera to do your bidding, not the other way round! Auto exposure controls are generally adjusted for the average, but many routine pictures have characteristics that fall outside the average, such as a bright sky and a dark foreground. The average exposure is often below the correct level for the sky, so it comes out white, and above the correct level for the foreground, so it comes out dark. In this case, we can manipulate the camera and get it to do our bidding.

To expose correctly for the sky, aim the camera at the sky, lightly hold down the shutter, reposition it and take the shot. To expose correctly for the dark foreground, aim the camera down, and do the same. We now have two pictures that can be merged into one in image editing later

Many cameras have auto-exposure compensation. However, if you’re aiming at a dark subject against a light background, then you can set the compensation to the plus setting, making it overexpose, and vice versa. Apart from switching off the flash, there’s not much you can do to manipulate the autoexposure settings, so if you really want to take control, then it may be an idea to get a higher specification camera.

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The answer is not to scan prints, but to either use a film scanner or to have your film scanned by some of the excellent scanning services that are available. Despite advances in digital camera technology, film remains an excellent medium for the capture and storage of picture information. It doesn’t matter whether the film is colour or monochrome, negative or slide.

A high-resolution film scanner will extract an enormous amount of information from the film and turn it into digital format.

A print is a copy of an image on film. In the analogue world, every time you make a copy you lose information. In the case of a print from a negative, it’s possible to lose over half the picture information – bright and detailed clouds burn out to patches of white, shadow detail is reduced to a dark pool of black and sharp edges are softened. If the colour balance isn’t right because the chemicals haven’t been topped up correctly, you lose colour information.

So why bother making a print? Well, a print contains more than enough picture information for our eyes to extract and we tend not to notice the lost information. We may not realise that it’s a bad copy of a negative or slide – after all, the film is too small for our eyes to read and you’re unlikely to be able to make sense of a negative.

The problem starts when, often using a low-cost flatbed scanner, we make a copy of what is already a rather ropy copy.

The best way to see the difference is to compare an image scanned from a print on a flatbed with one scanned from film. The answer is clear – always try to scan from film!

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Printing services often crop photographs, removing a strip off all four edges.

A more serious problem may be a mismatch between the shape of the window or frame used at image capture to the one use at printing stage. Cameras use many aspect ratios, ranging from panoramic to square. If you capture an image using one aspect ratio and wish to display it using another, then you have two choices: either include the entire image with blank borders or crop it so it fills the new frame size.

We encountered this problem when we made a 6 x 4-inch print of a picture captured using a popular digital camera. Most digital cameras use an aspect ratio of 4 x 3 (that is, computer screen aspect ratio), but the smallest standard print format uses an aspect ratio of 3 x 2 (the same as 35mm film). If you don’t want blank borders, then you have to crop. If the picture was originally 1,200 pixels wide and 900 pixels high, you’ll need to crop the picture at the top and/or at the bottom reducing it to 800 pixels. See our print techniques article later on.

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All marriages are not perfect. This information has been widely understood by many couple. Yet, many people think divorce as the only way out from an uncomfortable marriage without realizing the repercussions of divorce - financial and others. How much pain is too much to handle? If you’ve been married for two years, give it another two years. And if you already have five, give it another five. Divorce is a problem in itself. You should rather give yourself time to patches your pain. There are just so many people who said that if they knew then what they know now, they would have rather kept the marriage and worked things out.
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Despite the convenience of rescue tools found in image editing applications, there’s no substitute for getting your exposure right first time. Tim Daly reveals how

Correct exposure is achieved through the right combination of aperture and shutter speed, and makes a world of difference to your final image quality. Every digital camera has a built-in light sensitive meter, which is used to determine all auto exposure functions and, on more advanced cameras, the manual exposure readout in the viewfinder.

Light meters can only respond to the brightest values in your subject, regardless of their size, shape and colour, which means they can be fooled by everyday situations. A perfect exposure results when the photographer guides the meter into capturing a balance of highlight and shadow detail. Too much or too little light will have a profound effect on image detail, tone and colour reproduction.

Aperture, shutter speeds and ISO

These three independent variables are entirely interlinked and when one is changed, another needs to be changed to compensate. In addition to the creative consequences of using these scales, their primary function is to enable the photographer to shoot photographs in widely different lighting conditions. The ISO scale sets the sensitivity of the image sensor and works in an identical way to ISO speed in conventional film. At low light levels, a higher ISO value like 800 is best selected, so the sensor can operate with less light than normal.

At bright light levels, a smaller value like 200 is set. On basic digital compact cameras, the ISO value is fixed, but better models have a selection of different values such as 100, 200, 400 and 800.

Once your sensitivity has been set, then the right combination of aperture and shutter speed is sought to make a good exposure. The aperture is in your camera lens and is essentially a hole of varying size designed to let more or less light reach your sensor.

Apertures are a uniform size on all cameras and conform to an international scale described as f numbers like f2.8, f4, f5.6, f8, f11, f16 and f22. At the f2.8 end of the scale, an aperture is at its largest and lets in the most amount of light available. At the opposite end of the scale, such as f22, an aperture is at its smallest and lets in the least amount of light. To accompany the aperture scale is the shutter speed scale, again designed in a standardised range, but in fractions of a second such as 1/1000th, 1/500th, 1/250th, 1/125th, 1/60th, 1/30th, 1/15th, 1/8th, 1/4, 1/2 and 1s. At the 1/1000th end of the scale, the shutter remains open for short time, but at 1/2 second, the shutter remains open for longer.

Metering systems

There are three common metering systems used in digital cameras. Centre weighted on the left, matrix in the middle and spot metering on the right.

Most digital compacts use the functional rather than foolproof centre weighted metering. Centre weighted metering works by making an exposure judgement based on subjects that are placed in the centre of the viewfinder. This is perfectly adequate for centrally placed compositions, but can come unstuck if you intend to frame your subjects off-centre.

The much better matrix or segment metering system is designed to cope with the greater demands of more adventurous photographers. It works by taking individual brightness readings from the four quarters of your frame, plus an extra one from the centre. These five readings are then averaged out into a single exposure reading, resulting in a better balance.

The more complex spot metering system takes a reading from a much smaller area, typically the tiny centre circle superimposed in your viewfinder. Useful for getting accurate light readings from skin tones or other small and precise elements of a composition, a successful spot reading will emphasise this over other less important parts of your image.

Where to take your readings

The camera meter never knows which is the most important part of the image. It can only respond to variations in brightness so you have to trick the meter into behaving differently. With so many different levels of light reflecting off objects, the best exposure is a trade off between recording simultaneous detail in both highlights and shadow areas.

Most good digital compacts have an exposure lock button located close to your shooting hand, or accessible when the shutter is half-depressed. Exposure lock enables you to take meter readings from the important areas of your image, save the reading then recompose before shooting.

Camera histogram

All digital SLRs and quality compacts offer the benefit of a Levels histogram where an image is played back on the rear LCD preview monitor. If you find it hard to judge if your image file is overexposed, check its histogram. The histogram shows the quantity of pixels on the vertical scale together with their brightness values along the horizontal scale. At the left-hand end of the graph there is the shadow point with the highlight point set at the opposite right side. As each image is recorded, it’s possible to judge exposure by looking at the histogram. If this function is not available on your camera, it can be accessed via the Levels dialog in your image editor.

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To take control of your image sharpness, you need to get to grips with depth of field. Tim Daly shows how it’s an easy way of improving your photographs

Determined by your lens aperture setting and your proximity to the subject itself, depth of field is unique to photography. When looking around us, the human eye focuses so quickly on subjects at different distances that we hardly notice any transition. In fact, we are blissfully unaware that we can’t keep sharp focus on a close-up object and the distant background simultaneously.

With photography, however, you can create an image that presents more information to the human eye than happens in reality.

Depth of field is a photographic term used to describe the range in which two objects at different distances look equally sharp, and can be varied from a matter of millimetres to infinity. To use this technique, you need to control the aperture.

Aperture and depth of field

The aperture is a variable-sized circular opening inside your camera lens used to moderate existing light levels for a successful exposure, and it also determines depth of field. A typical lens has an aperture range like f2.8, f4, f5.6, f8, f11 and f16.

In terms of controlling exposure, an aperture of f2.8 is the widest and lets in the most amount of light. At the f16 end of the scale, the aperture is at its narrowest and lets in the least amount of light. In depth of field terms, f2.8 produces the shallowest result with little sharp detail beyond your chosen subject. At the f16 setting, sharper detail is rendered both in front of, and beyond, your main subject.

On budget digital compacts there’s usually a reduced set of apertures to choose from, such as f4 and f11. On better compacts this will extend to five or six options, with a full range available on the top-price SLRs. Aperture values are usually accessed via a thumbwheel or menu on the rear of the camera body, but can only be selected in manual or aperture priority exposure modes. In auto and other programme modes, the camera meter decides on an appropriate aperture value to generate a correct exposure, without taking your depth of field wishes into account. The aperture priority exposure mode lets you take control of depth of field and leaves you to select a shutter speed.

The other factor in creating depth of field effects is your distance from the main subject. If a landscape image is divided up into foreground, middleground and background, then it’s important to realise that you can’t separate objects lying in the same plane with shallow depth of field effects. As subjects get further into the background, it becomes harder to assign sharpness to one element and not the other. For mid-range zoom lenses found on most digital compacts, anything more than five metres away will record with a similar level of sharpness as the furthest parts of the scene.

Focus points

Especially important when focussing at close range is a third factor: your exact point of focus. A common mistake when shooting portraits is to focus on the nearest part of your sitter, usually the tip of the nose, which can leave the eyes slightly unsharp. Instead, pick the nearest and furthest parts you want sharp, then focus one third of the way in.

Depth of field doesn’t remain constant throughout the far-reaching landscape and close-up photography. As you get closer and closer to your subject, the effective depth of field diminishes until it can be reduced to a matter of millimetres – even at maximum f16. If you want to capture detailed images at close range your small apertures will force you to use slower shutter speeds than normal, and necessitate the use of a tripod.

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As with a traditional camera, the more you pay for your digital camera, the more features and better quality images you will get. Bear in mind that digital cameras are more expensive than their traditional equivalents so don’t expect to get printquality images from a digital cameras that costs less than £200.

If you just want to try out digital photography for fun and only intend to use the images to email to friends and relatives or upload onto your website, then a simple point-and-shoot camera with relatively low resolution may suit you fine.

If you want to use your digital cameras as your main camera and intend to order prints of some of your images to put in an album, then you are going to need to consider one of the megapixel cameras currently on the market. These range from simple point-and-shoot cameras to fully featured SLR-style ones.

Resolution

The resolution refers to the number of pixels captured by the camera’s image sensor or CCD. Early digital cameras and those at the low end of the market have what is known as VGA resolution with 640 pixels across the image and 480 down.
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