Canon PowerShot G12 Review Your Shots

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One of the greatest features of a digital camera is its ability to give instant feedback. By reviewing your images on the camera’s LCD screen, you can instantly tell whether you got your shot. This visual feedback allows you to make adjustments on the fly and make certain that all of your adjustments are correct before moving on.

When you first press the shutter release button, your camera quickly processes the shot and then displays the image on the LCD display. The default setting for that display is only two seconds. Personally, I don’t find this to be nearly enough time to
take in all the visual feedback that I might want. Instead of using this “quick glance” method, change your display time to the Hold setting. This will keep the image up on the display until you decide that you are ready to move on to your next shot. (Note that this option will drain your batteries a little faster than the default setting.)

Changing the Review Time setting

Changing the Review Time setting

  1. Press the Menu button and, in the Shooting menu, navigate to the Review setting.
  2. Use the Right button to select the Hold option (or choose an increment, up to 10 seconds).
  3. Press the Menu button again to return to the shooting mode.

When reviewing your images in Playback mode (by pressing the Playback button), four display modes give you different amounts of information. The default view displays only your image.

The basic shot information.

For more visual feedback, press the Display button to scroll through the other display options. Press it once to see the photo’s Quality setting, the image number that you are currently viewing (“3/207” would mean that you’re looking at the third image of 207 total images) and its file name, the time and date of the shot, and the camera’s battery level (Figure 1.5).

Pressing the button a second time results in a huge amount of information being displayed along with the image. You will now be able to see the following items in your display: shutter speed, aperture, exposure compensation, image name, image thumbnail, histogram, shooting mode, ISO, white balance setting, quality setting, size of the image in megabytes and pixels, image number, date, and time (Figure 1.6). This display also shows “blinkies,” or areas that are blown out with pure white

This display mode offers you a lot of information at a glance.

You probably won’t want to use this display option as your default review mode, but if you are trying to figure out what settings you used or if you want to consult the histogram (see the sidebar “The Value of the Histogram,” just ahead), you now have all this great information available.

The fourth display option shows you the Focus Check display.

The Focus Check display shows a magnified area of the image, allowing you to confirm that you’ve achieved sharp focus in your image (Figure 1.7).

Pressing the shutter release or Menu button results in closing the image display. To get your image back up on the LCD screen, simply press the Playback button on the back of the camera.

The value of the histogram

Simply put, histograms are two-dimensional representations of your images in graph form. The G12 offers a luminance histogram when you’re shooting (press the Display button to view it), which is valuable when evaluating your exposures. In Figure 1.8, you see what looks like a mountain range. The graph represents the entire tonal range that your camera can capture, from the whitest whites to the blackest blacks. The left side represents black, all the way to the right side, which represents white. The heights of the peaks represent the number of pixels that contain those luminance levels (a tall peak in the middle means your image contains a large  mount of medium-bright pixels). Looking at this figure, it is hard to determine where all of the ranges of light and dark areas are and how much of each there are. Looking at the histogram, you can see that the largest peak of the graph is in the middle and trails off as it reaches the edges. In most cases, you would look for this type of histogram, indicating that you captured the entire range of tones, from dark to light, in your image. Knowing that is fine, but here is where the information really gets useful.

This is a typical histogram, where the dark to light tones run from left to right. The black-towhite gradient above the graph demonstrates where the tones lie on the graph and would not appear above your camera histogram display.

When you see a histogram that has a spike or peak riding up the far left or right side of the graph, it means that you are clipping detail from your image. In essence, you are trying to record values that are either too dark or too light for your sensor to accurately record. This is usually an indication of over- or underexposure. It also means you need to correct your exposure so that important details will not record as solid black or white pixels (which is what happens when clipping occurs). There are times, however, when some clipping is acceptable. If you’re photographing a scene where the sun will be in the frame, you can expect some clipping because the sun is just too bright to hold any detail. Likewise, if you are shooting something that has true blacks in it—think coal in a mineshaft at midnight—there are most certainly going to be some true blacks with no detail in your shot. The main goal is to ensure that you aren’t clipping any “important” visual information, and that is achieved by keeping an eye on your histogram.

Take a look at Figure 1.9. The histogram displayed on the image shows a heavy skew toward the left with almost no part of the mountain touching the right side. This is a good example of what an underexposed image histogram looks like. Now look at Figure 1.10 and compare the histogram for the image that was correctly exposed. Notice that even though there are distinct peaks on the graph, there is a more even distribution across the entire histogram.

This image is about two stops underexposed. Notice the histogram is skewed to the left.

This histogram reflects an image with better exposure.