Coffeestops!

What is an aperture?
An aperture is a hole or an opening in the lens that admits light into the camera.

Where is it indicated on my lens?
Taking the Nikon 70-210 mm f/4-5.6 lens as an example, the minimum aperture for the lens is indicated by the “f” value found on the side of the lens. Some lens have it written on the front. The f/4-5.6 indicates the minimum aperture value of f/4 at 70mm and f/5.6 at 210mm. This applies to other lenses as well. Take note that it indicates the minimum aperture, hence values above that can be used.

Shown in the picture above is the Nikon 70-210 mm f/4-5.6 lens

What do the different “f” values mean?
The “f” values indicate the size of the opening of the aperture. While taking pictures, it is indicated in the viewfinder and/or on the LCD screen. Strangely, the bigger the “f” value, the smaller the opening is and vice versa. This however can be explained by the formula F/D, where F is the focal length and D is the diameter of the aperture. I doubt that you’ll be needing that for photography.

Shown in the picture above is the Nikon 70-210 mm f/4-5.6 lens at f/4 (left) and f/32 (right)

Where do I set the “f” value?
The size of the aperture can only be changed manually by cameras that have the “manual” function. Most consumer cameras do not offer the “manual” function. For cameras that do, they are usually those that favour functionality over aesthetics. To set the aperture size, simply switch to either aperture priority (Av) or manual (M) mode. Turn/press the dial/button to the desired “f” value.

How does the size of the aperture affects my photographs?
The size of the aperture affects images produced in different ways. For example, it affects the depth of field and the amount of light that passes through. Only two of the noted examples will be discussed in this article.

Depth of field?
Depth of field (DOF) is the portion of an image that appears to be sharp and focused. Remember those portrait shots with the background blurred out? It is done by changing the aperture to create a shallow DOF. The effect of different aperture on the DOF is shown in the pictures below.

Shown in the picture above is a 12 inch steel ruler taken at f/5.6 (left) and f/18 (right)

When do I need a shallow DOF or a deep DOF?
A shallow DOF is usually applied when you want to isolate distracting elements from the intended subject. As mentioned above, it is commonly used for portraits. As for a deep DOF, it is applied when we you to include every subject in the picture. For instance, a vast flower field or a group photograph.

Can you spot the metal wires between the camera and the bird? It is barely visible due to the shallow DOF (f/5.6 was used) in this picture (left). A deep DOF (f/10 was used) is needed to include everybody in this group photograph (right).

Amount of light?
Logically speaking, a large aperture allows more light in. Ever wondered how to decrease the exposure time (it is commonly called shutter speed but exposure time should be the correct term as the shutter always closes at a same speed) without using flash or increasing the ISO? Well you guessed it right! A larger aperture! This allows photographs to be taken under poor lighting conditions eliminating the use of flash. However, there are limitations to it. You can’t expect your camera to produce a well exposed picture that is taken in pitch black at a reasonable exposure time can you?

Conclusion?
Use a large aperture when you want your subject to stand out or when taking photographs in poor lighting conditions. Use a small aperture when taking sceneries or group photographs. However, do not limit yourself to these set of rules! Be creative!

Last 5 posts by Christopher

• Dragonfly - January 7th, 2009
• FGA USJ Countdown to 2009 - January 5th, 2009
• Blessed New Year! - January 1st, 2009
• Merry Christmas! - December 25th, 2008
• Shanghai Day 10 - December 24th, 2008