Digital SLRs exposed

The best photographs are captured by single-lens reflex cameras. Here’s how to make the most of your digital SLR

Most amateur photographers have compact digital cameras but single-lens reflex (or SLR) models are growing in popularity.

Digital SLRs, or DSLRs for short, are physically bigger than traditional compact models and the major external difference is a removable lens, which can be swapped for models with, say, wider coverage or greater magnification.

DSLRs also offer full manual control for great creative options and are much more responsive than compacts, so no more delays or missed shots.

Inside the body, the photographic sensor may have a similar number of megapixels to the one in a compact camera, but it’s physically much larger - with around 10 times the surface area. This makes DSLRs more sensitive to light, which means much better image quality in dim conditions.

So, DSLRs have justifiably become the preferred camera for anyone who’s passionate about photography, and in this Masterclass we’ll explain how to make the most of their many benefits.

Staying focused
All DSLRs can auto-focus, but they don’t always get it right - and unlike compact cameras, a badly focused DSLR image can look much more blurred.

First make sure the viewfinder is set up correctly. Most DSLRs have a small dial next to the viewfinder which can be adjusted to suit different eyes. Adjust this until the numbers seen below or to the side of the viewfinder image are sharp.

In terms of auto-focus, all cameras are getting better, but many still get confused by off-centre subjects. The trick is to lock the focus. To do this, first point at the subject, then press the shutter release button halfway, as this will lock the focus. So with the shutter button held halfway down, recompose the shot, then press it all the way down to take the photo.

This will take some practice, but any mistaken photos can, of course, be deleted. It’s a useful lesson to learn, and works with any camera.

Controlling the amount in focus
Some photos have everything from near to far in sharp focus. Others may only have the main subject in focus, while the background is blurred. The range of distances that are in sharp focus is known as the depth of field, and it’s easily controlled on a DSLR.

The depth-of-field is controlled by an adjustable iris in the lens. As this iris gets smaller, the depth-of-field increases and a bigger range of distances becomes sharp. As the iris gets bigger, the depth of field decreases and a shorter range of distances becomes sharp.

The iris is also known as the aperture and can be adjusted in Aperture Priority mode; this is still automatic with the camera working out the correct exposure to match. To use Aperture Priority, turn the DSLR’s mode dial to A (or Av on Canon camera).

The aperture itself is represented by an ‘f-number’ on the DSLR’s screen or in the viewfinder. The numbers vary between lenses, but typically go between f3.5 and f22. The smallest f-number means the aperture is wide open, while the biggest f-number means the aperture is at its smallest.

So if you want to have lots of the picture in focus, for example in a landscape shot, choose a big f-number, like f16. And to only have the main subject in focus, as in a portrait with a blurred background, choose the smallest f-number available, like f4.

One thing to watch out for is when the f-number is big, the iris is small and therefore not letting in much light. The DSLR will automatically compensate for this with a slower exposure, but this runs the risk of camera shake - so when using big f-numbers, always hold steady or use a tripod.

Freezing or blurring
Along with controlling the aperture, DSLRs also make it easy to adjust the shutter speed. This represents the time during which the sensor is exposed. A quick shutter speed can be used to freeze action, while a slow shutter speed can be used to blur movement.

The shutter speed can be adjusted in Shutter Priority mode, where, like Aperture Priority, the camera works out the correct exposure. To select Shutter Priority turn the DSLR’s mode dial to S (or Tv on Canon models). Typical shutter speeds are normally a fraction of a second, such as 1/250 of a second. Most DSLRs offer shutter speeds as quick as 1/2,000 of a second, or as slow as several seconds.

To freeze sporting action try a shutter speed of at least 1/250, or if it’s really fast, you may need 1/500 or 1/1,000. Fast shutter speeds won’t let much light into the camera, so need to be compensated with a large aperture and bright conditions. If there’s not enough light even with the aperture wide open, the DSLR will flash the f-number as a warning. If this happens, to avoid a dark photo either reduce the shutter speed, brighten the light or increase the camera’s sensitivity - we’ll explain how later.

Sometimes freezing the action in this way can produce a static-looking photo, whereas blurring can give a better impression of motion. To blur an action shot, try a shutter speed of 1/60 or below, although beware of camera shake at slower speeds. A great technique to try with racing cars, horses or anything else zooming past is to choose a slow shutter and follow the subject in the viewfinder as the picture’s taken. This will keep the subject sharp, but the background will blur, giving a feel of speed. We explain exactly how to do this in the step-by-step guide on the following page.

Another trick to try is with waterfalls or rivers. Slower shutter speeds will blur the water, making it look like steam and giving a dreamy effect. Shutter speeds of around one-quarter of a second are great for this, but the camera will need to be rested on a tripod or a ledge to avoid camera shake. When doing this, use the self-timer to avoid shake as the button’s pressed.

Adjust the sensitivity
All digital cameras can adjust the sensitivity of their image sensors, allowing them to work better in low light. The sensitivity is expressed as an ISO number, with most cameras offering a range from 100 to 1,600 ISO.

Doubling the ISO number doubles the sensitivity, but as it increases, so does ‘noise’ - this looks like random coloured speckles. Most compacts begin to lose quality beyond 200 ISO, but because of their physically larger sensors, DSLRs can generally match this quality at 800 ISO or higher.

So if you’re taking a photo at night or in dim conditions, or need a faster shutter speed to avoid camera shake or to freeze fast action, consider temporarily increasing the sensitivity. An ISO setting of 400 will give a good boost while maintaining quality, but for darker conditions or faster shutters, 800 or 1,600 ISO may be required.

Store in Raw?
As standard, all digital cameras record their photos in the JPEG format. It works well, but most DSLRs offer an alternative that can deliver greater quality and flexibility. This format is called Raw and can normally be selected in the image-quality menus; some DSLRs even give the flexibility of recording both a Raw and a JPEG at the same time.

Raw files simply take information from the sensor before it has been processed with colour, sharpness and tonal settings. This means a Raw file needs to be processed on a computer before you can use it, but most DSLRs come with software to do so. In the Raw software the exact amount of sharpness, colour and many other settings can be applied or adjusted. There’s also normally more latitude for adjustment than a JPEG.

Since Raw files take up more memory than JPEGs and require processing, many photographers only use them for special shots. On these occasions the extra flexibility and quality can be beneficial.

Watch out for dust!
One of the major benefits of a DSLR is the ability to change the lens for a different perspective, but this can also be their Achilles’ heel. When the lens is removed, dust and other foreign particles can enter the body and stick to a filter in front of the sensor. They then cast shadows onto the sensor, causing slightly fuzzy blobs that are more noticeable in areas of flat colour, like a blue sky.

Many DSLRs feature anti-dust facilities, but they’re rarely 100 per cent effective. Luckily most dust particles can be eliminated with a little manual intervention using an air blower tool - these cost only a few pounds. Remove the lens, hold the camera face down, and after following the sensor-cleaning instructions in the manual, squeeze some air into the camera.

It’s important to avoid compressed air as this can leave a residue on the sensor’s filter. Also ensure the blower doesn’t have a brush on the end and always blow from outside the body. If in doubt, take the camera to a shop for professional servicing.

Snap happy
We’ve only scratched the surface of what’s technically possible with a DSLR here. The real fun is getting out there, taking photos and experimenting with different settings. The beauty of digital is being able to check the results immediately and make adjustments if necessary.

Try exploring each shot, not only with different settings, but also different angles. Don’t be tempted to stand still and zoom the lens. Try getting closer or further from the subject or changing the height for completely different effects.

It’s also great practice to try and emulate photographers or photos that you like. To avoid any nasty surprises, always set the camera back to Auto or Program mode for automatic operation after any creative photography, and if necessary set the ISO sensitivity back to automatic or a low value. This way the camera will always be ready for action.

DSLR cameras to suit all budgets
After starting out as expensive tools for the professional, there are now DSLRs to suit every budget. Canon’s EOS 400D, for example, was the best-selling DSLR of last year. It has 10-megapixel resolution, a 2.5in screen, and access to Canon’s wide range of lenses. It’s a good solid model and costs around £399 including lens.

Those on tighter budgets should consider Nikon’s D40. It may offer ‘only’ six megapixels, but that’s enough for great-looking A4 prints. It also has an easy-to-use menu system for beginners. It’s superb value from as little as £299 with a lens.

Finally, the feature-packed 10-megapixel Olympus E-510 has built-in anti-shake facilities and a Live View mode, which allows composition with the screen. It’s remarkable value from £499 with not one, but two lenses supplied.

Here's our step-by-step guide to blurring action shots