Three basic settings on your camera sets the exposure. You need to understand exposure if you want to venture out of the auto mode on your camera and become a better photographer. This image of Quiraing on Isle of Skye is a good example of how difficult it can be! It took several shots to get it right.
You can leave your camera on auto mode and it a good place to start with you new digital camera. Many of the shots will look great but I’m sure you will realize that some are not exactly how you expected – some are too dark or too light, blurry or simply out of focus. As cameras get more advanced they generally do a good job getting the exposure right – but then why do we need to learn about exposure and not just let the camera do what it doing?
Simply because you want to be a better photographer and improve you skills and have more fun! – and the camera do not always know what you “really” want to show with your photos.
You can read a whole book about “Understanding Exposure” but I’m not big fan of big books I think it’s more fun to get out and learn by doing, have fun and do what you love. This way I’m sure you will learn to shoot great photographs with any camera from the iPhone to the most advanced digital SLR cameras.
Above you can see a landscape image that is over, correct and under exposed. Simply said “the exposure” is is a combination of three settings on your camera – shutter speed, aperture and ISO sensitivity. You will often hear experienced photographers and read that images is either over, correct or under exposed.
In the following I will explain the three fundamental concepts I thing you need to understanding to get well exposed images!
The shutter speed is the duration under which the photo is captured on the image censor – it’s the time it takes to capture the image. The shutter speed can be as small as a tiny fraction of a second up to several seconds or minutes. It impossibly to say what is the correct shutter speed it will depend on the situations and what effect you want to archive in the final photo.
To illustrate I will show you a few examples. In the photos below the shutter speed in the first image (to the left) is 1/4 of a second on the image to the right the shutter speed is 1/1000 of a second.
In the examples above I have used two very different shutter speeds on two pictures in the same category. In the first image I wanted to put emphasis on the movement and speed of the tram hence a slow shutter speed (1/4). In the second image I used a fast shutter speed (1/1000s) to capture the NYC taxi at the right place in the fog.
Here is another example showing how you can play with water. Which one is the best depend on the mood and what you want to show with you images. The shutter speed in the first image is 1/2 of a second on the image to the right the shutter speed is 1/50 of a second.
The aperture can be one of the most confusing aspects of photography for new photographers. In truth, aperture does not have to be a confusing.
Aperture is an adjustable opening inside the lens that works very similar the iris in your eye (Read about Aperture on Wikipedia). The element that confuses the topic is that when the aperture get larger (the physical aperture in the lens) the F value (the value you set on the camera) get smaller. For example a large aperture will have a low F value of 2.8 to 5.6 and a small aperture will have a F value of 16 to 22. Below the aperture value in the first image (to the left) is F 5.6 (a large aperture) on the image to the right the aperture value is F 22 (a small aperture).
In the example above the aperture is used to change focus in the images. In the first images with F5.6 the depth of field is very narrow and the focus is on the grass in the fore ground. In the second image with F22 the depth of field is large and you can see the grass and the houses in the background hence you eye is looking more into the background.
The important thing to remember is that F5.6 is a larger aperture which gives little depth of field compared to F22 which is a small aperture that give you a larger depth of field. In short if you shoot a big landscape use big F – if you want to isolate an object use a small F.
The ISO setting used to be something to do with the film in the camera but now-a-days it’s something to do with the sensor that captures the image inside the camera. I think of it as grain – the smaller and finer the grains the more you use to cover an area but you will be able to capture fine details (low ISO setting) – with larger grains you will need fever to cover the same area but you will lack the fine details (high ISO setting).
The ISO setting work the same way. If you increase the ISO setting you can use a faster shutter speed but the final images will be more grainy because some fine details are left out of the scene. Above you can see two examples with ISO 100 (left) to ISO 2500 (right).
Often you will aim for a low ISO speed around 100 – 400 but with many cameras you can easily use a much higher ISO setting without going on compromise with quality. Generally higher ISO settings are used in darker situations to get faster shutter speeds for example when you are indoor or outside in the evening and you want to hand-hold the camera without using flash. You can actually also use a very high ISO setting to get a certain “grain effect”. Today that grain effect is a common editing choice with programs like Adobe Lightroom or Apple Aperture.
I hope this small guide will help you understanding exposure. If you have suggestions or comments please let me know in the comments. You are also very welcome to share the guide if you find it helpful.