Archive for aperture

Photography Basics: Understanding Aperture

June 9, 2008 at 7:01 pm · Filed under aperture, f-stop, photography, photography basics


It’s been a while since I did a photography post, so I thought now was as good a time as any! So far in this series I’ve covered; Photography terms defined, shooting modes, understanding white balance, and window-light portraiture. Today’s photography lesson will be a more in-depth discussion about aperture.

The aperture is the hole through which the light passes through to reach the sensor or film. You can actually control the diameter of this hole on your camera. On old style cameras, there is an aperture ring that goes around the outside of the lens. Moving it around changes the diameter of the aperture.

You most likely will not have an aperture ring on your modern lenses, however, your lens still has the diaphragm inside that allows it to open and close, and you’ll have controls on on your camera that will allow you to control that diaphragm.

The numbers are called f-stops, moving up or down a stop halves or doubles the light let into the camera (the reason that the numbers look strange is down to some tricky math). Even though your camera doesn’t have an aperture ring, you’ll find that you can still adjust the aperture of your camera to these same values (although, depending on your lens, you might only be able to go as low as f4 or 5.6)

One thing that is really important to realize about the f numbers is that the smaller the number is, the larger the aperture is. This can be a bit tricky to grasp at first! If you increase the aperture by one stop (thus doubling the amount of light entering the camera), you’ll need to put the shutter speed down by one stop (and thus halving the amount of light entering the camera).

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Photography Basics: Lesson One

April 6, 2008 at 10:22 am · Filed under ISO, aperture, f-stop, photography basics, reciprocity, shutter speed

When first upgrading from a Point and Shoot digital camera to a Digital SLR, all the knobs and lenses and terminology can be quite intimidating. I don’t have any tips to make it easier, other than to practice, practice, practice!

Today we’ll start from the very beginning with exposures: apertures, shutter speeds, and ISO.

First, let’s define these terms.

Aperture~an opening that is used to control the amount of light passing through the lens of a camera. Typically constructed as an expanding and contracting iris. Measured in f-stops.

f-stop~values are the ratio of the focal length of the lens to the diameter of the opening in the aperture.

Shutter~a mechanism that sits in front of the focal plane in a camera and can open and close to expose the image senor or film to light.

ISO~a measure of a film’s “speed” or light sensitivity. The higher the ISO, the more sensitive the film. Digital camera sensors are also rated using the ISO scale.

OK, good, everything is now perfectly clear right?

As you increase your shutter speed, you need to decrease your aperture. This lets in more light compensating for the fact that the shutter is open for a shorter time. This relationship is called reciprocity because of the reciprocal relationship between the two values. Apertures and shutter speeds typically double with each setting.

Confused yet?

The higher the ISO rating, the more sensitive the film is to light. A film with a higher ISO rating doesn’t need as long of an exposure to make an image. A high ISO rating facilitates shooting in low light situations and in bright daylight with faster shutter speeds and smaller apertures. The drawback is that faster film means images with lots of grain.

ISO is the third factor you can control when using a digital camera giving them tremendous advantage over traditional film cameras.

Next topic: Shooting modes

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