The Lost Gardens of Heligan

Photography Tips - Part 2

10th November 2011

So last month we talked about the very basics of digital photography, explaining how your camera works, what a DSLR is, various lenses etc.

The next step now is exposure; what it is and how it works.

Exposure is essentially the amount of light recorded by your camera’s sensor whilst taking a photograph. It is governed by three things: Aperture, shutter speed and ISO.

Aperture: Aperture is the size of the lens opening. Aperture is measured in f/stops - a very wide aperture is f/2.8 and a very small aperture is f/22.

Shutter speed: Is the amount of time that the shutter is open during a single photograph. The shutter speed is measured in seconds and fractions of a second - 1/8000 of a second is very, very fast and 20 seconds is very slow.

ISO: ISO is your camera sensor’s sensitivity to light. The higher the ISO number, the more sensitive the sensor will be to light, and vice versa.

These three aspects work together to create the desired photograph, a change in any one of these will impact on the others.

You will quite often hear the terminology, underexposed and overexposed. When an image is underexposed it appears too dark and when it is overexposed it will be too light. Modern DSLRs have built in light meters, which accurately measure the amount of light in a scene and show it on your cameras display.

At first you will depend almost entirely on the light meter but once you know how to control your exposures you will be able to take better photos. Even though aperture and shutter speed both control the amount of light getting to the sensor they will also change other aspects of the photo. 

Shutter speed can be used to freeze motion with a fast shutter speed or it can be used to blur motion with a slow shutter speed. The photo of the coast was taken using a shutter speed of 30 seconds at ISO 100, f/11 whereas the photo of the Puffin was taken using a shutter speed of 1/1600 of a second at ISO 400, f/5.

Aperture also controls depth-of-field (DOF). Depth of field is basically the amount of distance between the closest and farthest objects that are in sharp focus. This can be used to draw viewers’ attention to one focus point by blurring the background by using a wide aperture (low f/stop). It can also be used to focus everything in the photo by using a narrow aperture (high f/stop), essential when photographing a vast landscape.

Below: The top photo was taken using an aperture of f/2.8 and the bottom photo was taken using an aperture of f/22

The final factor is ISO. All modern DSLRs offer the ability to change the ISO.  The most common span of ISO speed is from 100 to 800.  The higher the ISO the faster the camera is able to collect light. To achieve a fast shutter speed in most UK weather you will probably need to use a higher ISO setting (ISO 400 and above), also using a low f/stop will allow more light to reach the sensor, therefore resulting in a faster shutter speed. On the other hand when photographing landscapes etc. using a tripod you can get away with using a low ISO (ISO 100), you would then use a high f/stop to get a sharp image throughout, which in turn would give you a slower shutter speed. So in general, the lower the light levels, the higher the ISO should be.

One thing to bear in mind when using a higher ISO is that the image will get more digital noise. Noise is the digital equivalent of film grain, which shows up as lots of tiny coloured dots, which are much more noticeable in the darker areas of your photo. Note how the bottom photo (ISO 2500) has noticeably more noise than the top photo (ISO100)

One other factor that will affect your final image is White Balance.

White Balance is a part of photography that many digital camera owners don’t use, purely because they don’t understand it. It really is the difference between a good photo and a very good photo. White Balance is simply the control of the colour balance within an image, to get the colours as accurate as possible. Each scene and the different sources of light within that scene will have a slightly different colour (temperature). For example a photo taken in fluorescent lighting will add a blue cast to your images, therefore not accurately representing the scene. Our eyes automatically adjust for this change in temperature so we don’t notice it; the camera does not have this ability so we will sometimes have to help it out!

Many modern digital cameras have certain White Balance settings to make it easier. Below are some of the most common settings:

-       Auto – Your camera will evaluate the scene and automatically set the white balance, this tends to be very accurate except in the most difficult situations.

-       Daylight – a basic setting that will give a slightly warmer cast to your images, perfect for sunsets.

-       Cloudy – this setting tends to warm colours up a bit more than ‘daylight’ mode.

-       Flash – Used when using your camera’s flash. The flash of a camera tends to be quite a cool light, so this setting warms it up slightly.

-       Shade – the light in shade is quite blue, so this mode will warm the scene up a little.

-       Tungsten – this mode is for photographing indoors, under artificial light where the colour cast needs to be “cooled” down.

-        Fluorescent – this will “warm” up your photos by compensating for the ‘cold’ light of fluorescent lighting.

Below are two photos taken at the same time under the same light but using a different White Balance setting; note how the right-hand image has a nasty orange colour cast to it.

Hopefully that has given you a basic understanding of what is required to achieve an accurately exposed photo, to truly understand it I believe that experimenting is key. So get out there and play around.

Next time we will start to show you how you can use this knowledge to start taking great images at Heligan!