Introduction To Shutter Speed in Digital Photography

What is Shutter Speed?

– shutter speed is ‘the amount of time that the shutter is open’.

In film photography it was the length of time that the film was exposed to the scene you’re photographing and similarly in digital photography shutter speed is the length of time that your image sensor ‘sees’ the scene you’re attempting to capture.

• Shutter speed is measured in seconds – or in most cases fractions of seconds. The bigger the denominator the faster the speed (ie 1/1000 is much faster than 1/30).

• In most cases you’ll probably be using shutter speeds of 1/60th of a second or faster. This is because anything slower than this is very difficult to use without getting camera shake. Camera shake is when your camera is moving while the shutter is open and results in blur in your photos.

• If you’re using a slow shutter speed (anything slower than 1/60) you will need to either use a tripod or some some type of image stabilization (more and more cameras are coming with this built in).

• Shutter speeds available to you on your camera will usually double (approximately) with each setting. As a result you’ll usually have the options for the following shutter speeds – 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8 etc. This ‘doubling’ is handy to keep in mind as aperture settings also double the amount of light that is let in – as a result increasing shutter speed by one stop and decreasing aperture by one stop should give you similar exposure levels (but we’ll talk more about this in a future post).

• Some cameras also give you the option for very slow shutter speeds that are not fractions of seconds but are measured in seconds (for example 1 second, 10 seconds, 30 seconds etc). These are used in very low light situations, when you’re going after special effects and/or when you’re trying to capture a lot of movement in a shot). Some cameras also give you the option to shoot in ‘B’ (or ‘Bulb’) mode. Bulb mode lets you keep the shutter open for as long as you hold it down.

• When considering what shutter speed to use in an image you should always ask yourself whether anything in your scene is moving and how you’d like to capture that movement. If there is movement in your scene you have the choice of either freezing the movement (so it looks still) or letting the moving object intentionally blur (giving it a sense of movement).

• To freeze movement in an image (like in the surfing shot above) you’ll want to choose a faster shutter speed and to let the movement blur you’ll want to choose a slower shutter speed. The actual speeds you should choose will vary depending upon the speed of the subject in your shot and how much you want it to be blurred.

• Motion is not always bad – I spoke to one digital camera owner last week who told me that he always used fast shutter speeds and couldn’t understand why anyone would want motion in their images. There are times when motion is good. For example when you’re taking a photo of a waterfall and want to show how fast the water is flowing, or when you’re taking a shot of a racing car and want to give it a feeling of speed, or when you’re taking a shot of a star scape and want to show how the stars move over a longer period of time etc. In all of these instances choosing a longer shutter speed will be the way to go. However in all of these cases you need to use a tripod or you’ll run the risk of ruining the shots by adding camera movement (a different type of blur than motion blur).

• Focal Length and Shutter Speed - another thing to consider when choosing shutter speed is the focal length of the lens you’re using. Longer focal lengths will accentuate the amount of camera shake you have and so you’ll need to choose a faster shutter speed (unless you have image stabilization in your lens or camera). The ‘rule’ of thumb to use with focal length in non image stabilized situations) is to choose a shutter speed with a denominator that is larger than the focal length of the lens. For example if you have a lens that is 50mm 1/60th is probably ok but if you have a 200mm lens you’ll probably want to shoot at around 1/250.

Shutter Speed – Bringing it Together
Remember that thinking about Shutter Speed in isolation from the other two elements of the Exposure Triangle (aperture and ISO) is not really a good idea. As you change shutter speed you’ll need to change one or both of the other elements to compensate for it.
For example if you speed up your shutter speed one stop (for example from 1/125th to 1/250th) you’re effectively letting half as much light into your camera. To compensate for this you’ll probably need to increase your aperture one stop (for example from f16 to f11). The other alternative would be to choose a faster ISO rating (you might want to move from ISO 100 to ISO 400 for example).

By: Iskandar
Source: http://www.digital-photography-school.com/shutter-speed#ixzz1qI8ol71O

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What is Aperture in Photography ?

Aperture refers to an adjustable opening in your camera lens that is able to limit the amount of light passing through the lens and hitting the camera sensor. Just think of it like your eyes. When you open your eyes, light enters through your cornea, and is bent through the pupil, which is a round opening in the center of the iris. The iris and pupil works exactly like the aperture of a camera, controlling the amount of light being emitted.

To control your camera’s aperture, switch your camera mode to aperture priority. In this mode, you are able to manually control your camera’s aperture. The camera will change the shutter speed automatically to match the aperture that you had selected to create a picture that is properly exposed when the shutter release button is clicked.

Aperture is measured in F-stops. The lower the F-stop (e.g. f/2.8), the wider the opening of the aperture. While the higher the F-stop (e.g. f/22), the smaller the opening of the aperture. This concept can be confusing for beginners to understand as it is counter intuitive. However, it should not be too hard to understand once we know exactly what aperture is and how it affects the outcome of your pictures.

When the aperture is wide open (e.g. f/2.8), more light will enter through the camera’s lens, therefore, less time is required for proper exposure which meant faster shutter speeds. Wide aperture will also cause a shallow depth of field in your picture, where the foreground and background of your picture is blurred except for the subject which you are focusing on. However, the opposite applies when the aperture is small.

When the aperture is small (e.g. f/22), less light will enter through the camera’s lens, therefore, more time is required for proper exposure which meant slower shutter speeds. Small aperture will also cause a deep depth of field in your picture, where everything in the picture is in focus.

Wide aperture (e.g. f/2.8) is useful for taking pictures in low light conditions as more light gets to enter and hit the camera’s sensor. It allows you to use faster shutter speeds as well that can be used to freeze action on moving subjects such as a running dog. It is also suitable to use when you want to take portraits or macros where you want a shallow depth of field so that the subject will be sharp and stand out in your picture.

Small aperture (e.g. f/22) is useful for taking pictures in good light conditions as there is more than enough light that will enter and hit the camera’s sensor. It allows you to use slower shutter speeds which can be used to give your subjects a motion effect in your picture. Remember the running dog example? We can use slower shutter speed to create a motion effect of the dog, running in your picture, bringing your picture to live.

A small aperture is also suitable to use when you want to take landscapes or group shots so that everything in the scene is considerably sharp.

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ISO Settings in Digital Photography

In traditional (film) photography ISO (or ASA) was the indication of how sensitive a film was to light. It was measured in numbers (you’ve probably seen them on films – 100, 200, 400, 800 etc). The lower the number the lower the sensitivity of the film and the finer the grain in the shots you’re taking.

In Digital Photography ISO measures the sensitivity of the image sensor. The same principles apply as in film photography – the lower the number the less sensitive your camera is to light and the finer the grain. Higher ISO settings are generally used in darker situations to get faster shutter speeds (for example an indoor sports event when you want to freeze the action in lower light) – however the cost is noisier shots. I’ll illustrate this below with two elargements of shots that I just took – the one on the left is taken at 100 ISO and the one of the right at 3200 ISO (click to enlarge to see the full effect).

100 ISO is generally accepted as ‘normal’ and will give you lovely crisp shots (little noise/grain).

Most people tend to keep their digital cameras in ‘Auto Mode’ where the camera selects the appropriate ISO setting depending upon the conditions you’re shooting in (it will try to keep it as low as possible) but most cameras also give you the opportunity to select your own ISO also.

When you do override your camera and choose a specific ISO you’ll notice that it impacts the aperture and shutter speed needed for a well exposed shot. For example – if you bumped your ISO up from 100 to 400 you’ll notice that you can shoot at higher shutter speeds and/or smaller apertures.

When choosing the ISO setting I generally ask myself the following four questions:
1. Light – Is the subject well lit?
2. Grain – Do I want a grainy shot or one without noise?
3. Tripod – Am I using a tripod?
4. Moving Subject – Is my subject moving or stationary?

If there is plenty of light, I want little grain, I’m using a tripod and my subject is stationary I will generally use a pretty low ISO rating.

However if it’s dark, I purposely want grain, I don’t have a tripod and/or my subject is moving I might consider increasing the ISO as it will enable me to shoot with a faster shutter speed and still expose the shot well.

Of course the trade off of this increase in ISO will be noisier shots.
Situations where you might need to push ISO to higher settings include:
Indoor Sports Events – where your subject is moving fast yet you may have limited light available.
Concerts – also low in light and often ‘no-flash’ zones
Art Galleries, Churches etc- many galleries have rules against using a flash and of course being indoors are not well lit.
Birthday Parties – blowing out the candles in a dark room can give you a nice moody shot which would be ruined by a bright flash. Increasing the ISO can help capture the scene.

ISO is an important aspect of digital photography to have an understanding of if you want to gain more control of your digital camera. Experiment with different settings and how they impact your images today.

By: Iskandar
Source: http://www.digital-photography-school.com/iso-settings#ixzz1qI9mtZU9

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Metering in Photography

Learning to use the different metering modes on your camera is a skill well worth knowing as it puts in your hands more control in how your camera approaches capturing a particular scene.

Every time you point your camera at a scene it needs to take a guess at what is important to you in the picture and which part you want to be exposed optimally. The metering mode you have your camera set to will signal to the camera how you want it to approach this task.

Let me explain further by highlighting three main metering modes that you’ll find on many digital cameras (note – not all cameras offer this choice although all DSLRs do and many point and shoot cameras do):

1. Overall Metering (Multi Segment/Zone Metering)

In this mode the camera attempts to take into consideration everything in your frame. Most cameras will have numerous metering zones around the frame (for example the Canon EOS 5D has 35 points that it takes into consideration).

It assesses overall lighting from all these zones and takes a best guess by averaging them to decide on how to expose the shot. This mode is the one I used to leave my camera set to most of the time and it did give great results.

However, at times the camera guesses wrong and it’s useful to know how to use the other metering modes below to give your camera a little more information about what you’re trying to achieve.

2. Spot Metering



This mode tells the camera to do it’s metering from a very small ‘spot’ in the scene. Instead of taking information from all 35 zones, the 5D hones right in on one – ignoring all others. This is a very useful mode for tricky lighting conditions where the whole scene is either darker or lighter than the point that you want to be exposed correctly.

For example in a back lit situation where you’re taking a portrait of someone whose face is a little too dark. Without spot metering in this situation you might end up with a silhouette and not be able to make out the features of your subject. Spot metering gives you very exact control when there is a very specific (and small) part of the scene that you want to get right.

3. Center Weighted Metering


On the spectrum between overall metering and spot metering we find the Center Weighted Metering mode which takes a little from both ends of the spectrum and tells the camera to focus it’s metering decisions upon the center of your image (although a wider area than spot metering).

In Center Weighted Metering the camera will take information from numerous metering points around the frame but will give more weight to those in the center. Like spot metering, this is good to use in tricky lighting situations where you don’t need to identify very small parts of the image to meter on.

By: Iskandar

Source:  http ://www.digital-photography-school.com/introduction-to-metering-modes#ixzz1qI6zcB8T

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