Aperture

Since the last post, and accompanying video, dealt with shutter speed, I figured I'd better complete the discussion about exposure by making a video about aperture.

The aperture is the opening in the lens. The wider the opening, the more light that will be recorded on your film or digital sensor.

Take a look at the video, and the one of shutter speed. If you have any questions, please feel free to email me.

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Shutter Speeds

While this may seem pretty basic, I often get questions on what shutter speed and aperture are -- and how they relate to exposure - and to each other.

Shutter Speed is the time that the shutter remains open, when you press the shutter release button.

Exposure is determined by the combination of how long the shutter is open, and the size the lens aperture (opening).

Shutter speeds can range from one second (even longer if you have a B [bulb] option) to 1/4000th of a second on most prosumer cameras and higher on pro level cameras.

If you are shooting fast moving action, you will want to use faster settings. In low light, you will use longer settings, and may even need to put the camera on a tripod.

Here is a quick video demo of shutter speeds.

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Depth-of-Field

The depth of field (DOF) is the distance in front of and behind the subject that appears to be in sharp focus.

Have you ever wondered how professional photographers make their subjects stand out from the surroundings? While you can’t do this with a fixed focal length camera, you can do it with most consumer cameras, and will all SLRs (single lens reflex cameras – those with interchangeable lenses), if you have the right lenses.

For example, a flower may stand out against a blurred background, or a small insect is set against a blurred leaf. Perhaps, the most striking example is when a person seems to be almost detached from the background – they pop out of the page. Well, it’s not difficult to achieve this effect.

The trick is to use selective focus.

With this technique, we can choose one part of the image to be sharp and in focus, while the rest of the image is kept out of focus. It's very useful in macro and close-up photography.

So how do you achieve selective focus? Here are some tips.

Aperture Size

For selective focus, try choosing your widest f-stops (i.e. aperture size), such as f/2.8 or f/4. Couple this with a fast shutter speed to ensure enough light is present in the photo.

Focal Length

A good tip is to zoom (remember to only use the optical zoom –- not the digital zoom feature, if your camera has that option -- in as much as possible, or choose a telephoto lens. The longer the lens, the less depth-of-field it has -- conversely, the wider angle, the more DOF.

Angle to Subject

This tip takes a bit of practice, but is very effective at times. Choose an angle to the subject that causes background and foreground elements to be farther from the focused subject. This causes them to be strikingly out of focus.

Note that it is in fact possible to achieve the selective focus effect using image editing programs. You can simply select one part of the photo, keep it sharp and then blur the rest. However, if shoot the image with selective focus because the effect always looks more natural.

We will talk about achieving selective focus, with software, in another post.

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