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Ever wondered how your camera produces a "well lit" images every time you take a photo?
When you squeeze the shutter release button, you actually trigger 2 actions:
Auto focusing &
Exposure metering. Looking at Exposure Metering for a moment.
The camera uses it's light meter to calculate the amount of light needed to create a balanced
exposure.
So how exactly then does the camera control the correct amount of light needed?
Simply with the combination of two devices:
The Aperture
And the Shutter
The APERTURE, which controls "HOW MUCH" light is let in.
and
The SHUTTER, which controls "HOW LONG" light is let in for.
For example, in DARK conditions, where we need more light, the camera will either:
- Keep the SHUTTER open for a longer period of TIME
Or - Set a larger APERTURE to increase the AMOUNT
of light entering through the lens.
Both actions let more light in. In BRIGHTER conditions, where we need less
light, the camera will do the opposite.
It will:
Keep the SHUTTER open for a shorter period of time
Or
Set a smaller APERTURE to decrease the AMOUNT of light entering through the lens.
Both actions will allow less light in.
So what makes a good Exposure?
Simply, a good exposure is one that is not too light or too dark.
Lets look at these photos of the same subject.
The middle image is taken with perfect or "NORMAL" exposure
The top image is darker and "UNDER EXPOSED".
And the bottom image is lighter so is "OVER EXPOSED"
So why is exposure such a big deal? Exposure is not just about how bright the
image appears.
Good exposure gives great details.
Lets take a closer look... Take this UNDER exposed image for example....
While details in the bright areas are visible, they are lost in the darker areas
While in this OVER exposed image...
The details are burnt out and lost in the brighter areas, and retained in the dark areas.
However, in this CORRECTLY exposed image, the details are visible throughout both the
shadow and highlight areas.
So if getting the right exposure is so important, how do we do it?
The D-SLR is equipped with a great range of exposure modes to suit all users.
For beginners, it's easiest to start with the FULLY AUTO & PROGRAM MODES:
FULLY AUTO decides all settings for you, including flash.
PROGRAM Mode takes care of Shutter and Aperture, but leaves you to decide when to use the flash
and set ISO sensitivity. Here are a few examples of the preset modes:
SPORTS MACRO
PORTRAIT LANDSCAPE
and SUNSET
Lets have a closer look at each.
Freezing fast moving subjects is easy using the sports mode.
In order to achieve this, the camera needs to use high shutter speeds.
Once you set the camera in Sports action mode, it will choose the highest shutter speed possible
to help you freeze the image.
Macro photos like this are made compelling because of their defocused or blurred background.
This is technically achieved by using a large aperture.
Now, by using the Macro mode, the camera will use the widest aperture to blur the background
as you zoom in.
Great portraits have a blurred background and reproduce skin tones well.
Technically, the blurred background is achieved by using a large aperture.
And the skin tone is achieved by choosing a neutral colour balance.
When you choose the portrait mode, the camera is set up to use the largest aperture possible
and a neutral White Balance setting.
Successful LANDSCAPES have clarity throughout the image.
This clarity is achieved by using a small aperture setting.
When you use the LANDSCAPE mode, the camera will choose the smallest aperture possible
to help you achieve clarity throughout the whole image.
Sunset is probably the most beautiful time of the day.
It is full of rich warm hues and colours.
When in SUNSET mode, the camera will change the colour balance of the image to a slightly
more orange hue to intensify the colours of the sunset or sunrise.
Let's have a quick recap of what we have learnt in this tutorial.
- What is exposure? - How does the camera control light?
- What is the perfect exposure? - Choosing an exposure mode
- And, understanding exposure presets.
Now that you are familiar with basic exposure
Make sure you check out the other tutorials in the series, and see how else you can take
creative control of your camera.