Aperture

Aperture

Aperture means “opening.” The opening inside the camera’s lens is what lets light into the camera. Photographers refer to the size of this opening as the aperture. Aperture is adjustable in most cameras.

The aperture is calibrated in f/stops. Common f/stops are f/22, f/16, f/l1, fiS, f5.6, f/4, and f/2.8. Sometimes they are written with a dash, such as f-22. In spoken language the punctuation is not mentioned. F/22 would be spoken of as simply f 22.

The confusing part about understanding aperture is that it is written as a fraction with a letter instead of a number as the numerator (top). Apertures with a large number in the denominator (bottom number), like f/22, may seem to be something big but are actually “small.” So when a photographer talks about using a small aperture, the opening size is small but the f-stop has a large lower number.

When a photographer has “closed down” the lens, he/she has used an f/stop which does not let much light in, such as f/22. This is called a “small” f/stop. When a photographer “opens up” or shoots “wide open” to let in more light, he/she is using an f/stop such as f/2.8. This is called a “large” f/stop.

Aperture works together with shutter speed and ISO to form an ideal exposure. There is more than one combination that will produce an image with the same lightness and darkness. If the photographer starts with a set exposure, he/she could change the aperture to be more opened up. Then the camera would automatically choose a faster shutter speed in order to maintain the same amount of light entering the lens through the now larger opening.

When the ISO is changed, the camera’s sensitivity to light is increased or decreased. So the combination of aperture/shutter speed will change accordingly. The photographer may want to change the ISO in order to get the desired combination. Sometimes there is no shutter speed available for the chosen aperture. This usually happens in very dark or very bright lighting situations.