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Digital SLR cameras: a beginners users guide

A D-SLR, (Digital- Single Lens Reflex) camera is made from higher quality components than normal digital cameras and their image sensors are much larger, which means that the picture quality is far more accurate and true to life.

Unlike compact cameras, a D-SLR camera uses a pentaprism and optical viewfinder to take pictures, this ensures that you see exactly what the lens see before you take the picture without any distortion.
To understand more about D-SLRs it is important to understand the basic structure of the cameras and how they capture images.

  • When focusing on an image, light passes through the lens and hits the mirror.
  • This is then reflected up to the glass pentaprism (Which is sometimes referred to as mirror-prism or mirror box)
  • The pentaprism then reflect the image through to the optical viewfinder for the user to see what they are shooting.
  • When the user takes the photo, the mirror flips up, exposing the sensor to light and captures the image.

This process means that when the user looks through the optical viewfinder, s/he sees exactly what is being shot.

Live View

Some D-SLR cameras also feature Live View, this lets you preview the picture you are about to take on the LCD screen. Before you think “well can’t all digital cameras do that?” All digital compact cameras on the market do have this function but that is because they are built differently. However, live view doesn’t exist in all D-SLR cameras. This is because of the internal structure of D-SLR cameras.

Right here comes the techy bit… On an D-SLR that doesn’t have Live View, the mirror only flips up to allow light through to the sensor when the user takes the picture, this means that the rest of the time the mirror is blocking the light from the sensor and preventing the image from appearing on the LCD screen. The D-SLR cameras that do feature Live View have an added second sensor in the path of the light. This second sensor transmits the image to the LCD screen so the user can see what they are about to shoot which allows shooting pictures from the screen rather than using the view finder.

The LCD screen on cameras which do not have Live View is used to review pictures and to view the menu.

Creative control

A major advantage of D-SLR cameras is that they give you full creative control over the settings, so you can control the aperture, shutter speed and ISO. Here is a guide to how to use these settings. However, it is important to remember that all of these setting work together so to get the perfect shot these settings need to harmonised together.

Aperture priority

The aperture refers to the size of lens opening and how much light it lets in. By adjusting the aperture value you adjust the diameter of the lens. Aperture is measured in f-stops (Focal ratio), confusingly, the larger the aperture f-stop, the smaller the lens diameter and the less light is let into the sensor and the smaller the aperture f-stop, the larger the lens diameter and the more light is let into the sensor.

The above diagram demonstrates how the diameter of the lens changes when the aperture is adjusted. Changing the aperture allows you to control the depth of field; that is how much of the picture is in focus. The pictures below demonstrate this.

Look at the first image, here there is a larger aperture (lower f-stops), with a wide diameter and lots of natural light allowed into the lens. This has resulted in a shallow depth of field, so that the flower at the front of the picture is brought into sharp focus and the background is blurred, this helps the flower at the front stand out from the rest of the photograph.
Looking at the third image where there is a smaller aperture (higher f-stops) with a narrower diameter allowing less light allowed in to the sensor, this creates a deeper depth of field where the whole image is in clear focus. However, it is important to note that to balance the light in the picture a slower shutter speed is also needed here so that the image isn’t too dark and enough light is captured.

In summary, a large aperture has lower f-stops. The subject will be in focus and the rest image will be blurred.
A small aperture has higher f-stops. The subject and background will be in focus.

Shutter priority

This basically allows you to control the speed of the shutter. The speed of the shutter affects the amount of time that the sensor is exposed to light. The shutter opens and closes to allow or prevent light reaching the sensor and is controlled when the shutter release button is pressed on your camera to take a picture. The shutter speed determines how long the shutter remains open.

The speed of the shutter can affect the exposure of the picture. If the shutter is open for too long then the picture will be over exposed as there will be too much light. If the shutter is not open for long enough then the picture will be too dark.

The shutter speed can also give motion to a photo.
A fast shutter speed captures high-quality moving scenes, notice in the first image of the fountain the water looks as though it is frozen still and there is more detail in each drop of water. When using a fast shutter speed you will have to use a larger aperture or higher ISO setting so that enough light is let in to the sensor.

While a long shutter speed can give a creative blur to the photo. A longer shutter speed can also be used in situations where there is low light and you need to allow more light into the sensor.

When using a slow shutter speed anything that is moving in the shoot will blurr whilst a stationary object will stay in focus balance.

ISO

Back in the day when we all used film cameras ISO rating described different types of photographic film. In digital cameras the ISO determines how sensitive the sensor is to light. Always try to use as low ISO setting where possible as this produces images of better quality.

As a general rule of thumb you should use a low ISO of 100 or 200 when taking photographs outside in sunny conditions where there is lots of light.
If the sky is overcast or it is evening time, then use an ISO within the range of 400 to 800 and at night time or in cases of low light you might need to increase the cameras ISO set your digital camera ISO to 1600.

The higher the ISO the more able the camera is at taking photos in poor lighting, however a higher ISO can also leave the picture with a grainy effect. Therefore, to get the perfect shot the ISO needs to be balanced with both the aperture and shutter speed.

In essence, photography is all about light and controlling the light in the environment you are shooting in. All three elements; aperture, shutter speed and ISO, need to be synchronised to suit the shooting conditions. A D-SLR gives you the control you need over all these elements.


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