Photography
UNDERSTANDING MANUAL PHOTOGRAPHY
IT’S FRUSTRATING WHEN your camera doesn’t see the same image as you do. So why do cameras occasionally get it wrong?
A camera’s light meter is calibrated to 18% grey, which is the brightness value of the light reflected by an average scene in average lighting conditions. But when it’s faced with a non-average scene – an all-black or all-white subject, for example – the camera will over- expose the blacks and under-expose the whites. Understanding why the camera does this will help you identify the scenarios where getting correctly exposed images could be problematic.
Although the camera’s semi-automatic shooting modes (Program, Aperture Priority and Shutter Priority) offer a degree of user control, the camera is still responsible for some of the decision-making when you use these. For a decisive say in how your images look, you’ll need to use manual settings.
EXPOSURE SETTINGS
Exposure is determined by the inter-relationship of ISO, aperture value and shutter speed. But there’s more than one way to achieve the same exposure value (EV) – an exposure of 1/60 sec at f/16, ISO 100 is equivalent to an exposure of 1/1,000 sec at f/4, ISO 100. As you can see from the diagram (right), the combination of ISO, aperture and shutter speed is influenced by the look you want to achieve in the final image (the glass of water). Do you require a large or shallow depth of field (a trickle or torrent of water), or any moving objects to appear sharp or blurred (the tap on full for a short time, or on less power for longer)? Making corresponding adjustments to ISO, aperture and shutter speed will result in the same EV. To influence the appearance of the final image, you’ll need to change one of the values in isolation.