Technique PHOTO SCHOOL
29
Camera class
Howthe shutter inyour DSLRworks An DSLR has a focal plane shutter. This comprises two curtains. When you press the shutter button, the first curtain moves to unveil the sensor. A very short time later, the second curtain moves to cover the sensor and end the exposure. Effectively at short shutter speeds, the exposure is produced by a slit running across in front of the sensor – the speed of the shutter curtains is constant. The flash sync or X-speed is the fastest speed where the sensor is fully uncovered – 1/60sec in our example.
Everyone has to start somewhere, even top pros, and in our regular Photo School feature we’ll be taking a close look at core techniques that every beginner needs to know. This month, in Camera Class we look at the effects of shutter speed and how to control it, while Software skills (below) helps you take your first steps to enhancing your images in Adobe Lightroom
Words by Ian Fyfe
To illustrate shutter speeds, for clarity we used the dial of the Nikon Df. Your DSLR will have a very similar range, but you access them via an input dial.
to shoot longer exposures. Switch to Bulb (B) mode, and the shutter remains open for as long as the shutter button is held down – you do this with a lockable remote release. n What other effects does shutter speed have on my images? The length of time the shutter’s open for determines whether or not movement is recorded in your image. A fast shutter speed freezes fast-moving action, and a slow one captures movement as a blur. We’ll look at how to use shutter speeds creatively next time. The shutter speed is expressed as a fraction of a second, 125 is 1/125th of one second and 4000 is 1/4000sec, a very short exposure. Here the numbers in red are 1, 2 and 4 seconds. B: stands for Bulb. This setting lets you hold the shutter open with a locking remote release for as long as you like. Most DSLRs have timed shutter speeds as long as 30 seconds and B lets you shoot even longer ones, into minutes and even hours. T: stands for Time. You won’t find this on many modern cameras . It does the same job as B but works differently. In T, press the shutter release once to open the shutter; push it again to end the exposure. X: this is the flash sync speed, the fastest shutter speed for correct flash photography. You can use slower speeds but use faster ones and your image will only be partially exposed. See the panel right. Most DSLRs will by default let you set in-between shutter speeds in one-third steps – so from 1/125sec to 1/250sec, you can set 1/160sec and 1/200sec.
In the last two Camera classes, we’ve seen how you can use the aperture to control exposure and express your creativity. But to get the right amount of light to the sensor, the aperture must be balanced with the shutter speed. This time, we look at how the shutter speed affects exposure, and the different ways in which you can control it. n What is the shutter speed? When you press the shutter button, the shutter opens and the sensor is exposed to light. The shutter speed is simply the amount of time the sensor is exposed to light to allow an exposure to be made. See the panel opposite about how a DSLR focal plane shutter works. n What does this mean for my exposures? Like f/numbers, the steps available for the shutter speed form a standard scale related to the amount of light that’s allowed to reach the sensor. Each step from the slowest to the fastest shutter speed halves the time the shutter’s open for, and this halves the amount of light that reaches the sensor, so long as everything else stays the same. For example, changing the shutter speed from 1/125sec to 1/250sec halves the amount of light reaching the sensor, a change that’s equivalent to closing the aperture by one full f/stop. Modern cameras allow smaller shutter speed steps than are shown, ie. 1/3 stop (the usual default) or 1/2 stop. Software skills Shoot Raw for fine-tuning images. Part 4: Enhancements ADOBE LIGHTROOM More and more photographers are turning to workflow softwares such as Adobe Lightroom 5, Photo Director 5 and Corel AfterShot Pro for their organising, editing and outputting abilities. So far in Software skills, we’ve looked at library functions, now let’s look at editing. Lightroom 5 has seven modules, including Library, where images are organised, and Develop, where they are enhanced. There’s a lot to learn in the Develop module, so we’ll start simply. Words by Will Cheung
1/1000SEC
2nd
1st shutter curtain
1/250SEC
1/60SEC
n How can I control the shutter speed? If you want control of the shutter speed, the easiest way is to use shutter-priority mode (usually S or Tv on the dial). This lets you set the shutter speed to the value you want, while the camera automatically adjusts the aperture to give the correct exposure. You can set the shutter speed in manual mode, but you’ll need to adjust the aperture manually too. n What if I want longer shutter speeds? Most cameras allow shutter speeds of up to 30 seconds in normal shooting modes, but it’s possible
NEXTMONTH: More on shutter speeds and image enhancements
On the left are Presets. Here you achieve creative effects with a single mouse-click. You can make your own presets, or import those made by other people. Presets are a fast way to get an effect that you can then refine further should you want to. If you select a preset you don’t like, click on the History tab and go back to the original imported image. Any changes you make to a Raw file are virtual – the original Raw remains untouched. For stronger effects, create a virtual copy; changes are stored with the file and applied when it is outputted. On the right is the Basic tab. ‘Basic’ rather undersells the potential because there is a great deal you can do, including adjusting exposure, contrast and white-balance. Or you can make the image monochrome by clicking on Black & White. Adjust the various sliders to get a feel of what’s possible and the preview image updates instantly. To make your virtual changes a reality, ie. to produce a file you can print, email to your family or upload to a website, go to File>Export. Here you can decide where you want the file to be saved to and in which format (JPEG or TIFF) under File Settings. Click Export and you get an image file with all the changes you made in the Develop module.
ABOVE In the Develop module, the main enhancement controls are in the sidebar to the right. You can close both or either of these by clicking on the arrows at the extreme edge of the interface. TOP RIGHT Lightroom supplies a number of useful presets and it’s easy to produce your own or to import more from fellow image makers. BOTTOM RIGHT Open each option by clicking on the arrow to the right of the tab name, or disable/enable the control by clicking on the switch or to the left.
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Issue 4 | Photography News
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