February 1 2012
The concepts of f stop, shutter speed, and ISO can intimidate novice photographers in the jump from automatic scene modes to taking creative control of their digital photo’s exposure.
The fully automatic metering systems in modern digital cameras achieve exposure settings for reasonable images in ordinary conditions.
To take their pictures beyond the sameness of machine determined exposure and fully capture different situations – or as some put it give pictures that professional look – photographers need to take control of the camera.
These settings are a beginning of the photographer’s journey into creativity.
These recommended camera settings are based on my own experience. I use these settings as my starting point, so whenever I finish a series of pictures I set the camera back to these settings because they are a good general purpose settings for daylight outdoors exposure.
The order is meaningful and is usefull for most general photography, but not for sports or fast moving subjects.
This is the seemingly confusing setting is also know as the f stop, and this is a measure of the size of the opening in the lens that lets the light into the camera. The larger the aperture the more light enters the camera.
Confusing bit – the f stop goes backwards.
Smaller f stop number means a larger aperture, and large f stop numbers mean smaller apertures. Setting the lens to f5.6 means a large opening in the lens, while using f16 is a very small opening, restricting the amount of light coming into the camera.
In bright light photographers should use smaller apertures and in low light wider apertures are preferable. There are always buts in photography, and for aperture there are a couple.
On larger cameras effect of aperture on depth of field is quite noticeable. Large apertures (small f numbers) have only a small area in focus, while the areas in front of and behind the focus point are blurry.
The other restriction is the optical performance of the lens varies with aperture. Many lenses perform quite badly, with significant distortion and colour fringing, at wide apertures.
To achieve a good depth of field and minimise lens problems start with standard and wide angel lenses at f 7.
For landscapes, general photography and portraiture set the camera to Aperture Priority mode and let the camera set the shutter speed. As long as the shutter speed is 1/125 sec, or faster, then blurriness caused by camera shake is negligible.
For telephoto lenses a good rule is the shutter speed = 1/focal length, as camera movement is more apparent at long focal lengths. For a lens with a 35 mm equivalent focal length of 200 mm, set the shutter speed to 1/250 of a second.
If the shutter speed slows too much, widening the aperture with a lower f number lets in more light and increases the shutter speed. As a last resort use a higher ISO setting.
This is how sensitive the digital camera’s sensor is to light. As the light gets dimmer increasing the ISO setting makes the sensor more sensitive to light, so the camera can still take photographs.
Of course there is another but.
Raising the ISO increases the amount of digital noise in the image. Always use the lowest ISO setting, that gives a good combination of aperture and shutter speed, to minimise noise in the photos.