When making adjustments in Aperture, like most image-editing software, there is usually more than one way to arrive at the desired result.
To make sure your images are within the tolerances of the final print, it’s good to check yours histogram to see that information is not being “clipped”.
Pie eating without utensils. Copyright Steve Simon
If a histogram represents all the pixels in your digital capture, you can see when the shadows or highlights get pushed to the edge of the graph. This tells you that some areas of the scene in shadow on the left side, or highlights on the right, won’t be reproduced with any detail.
The wonder of raw is that you can often bring back this lost information, particularly in the highlights that would otherwise reproduce as pure white; but it helps to know where these extreme highlights or hot spots are in your image.
In Aperture, the shortcut for “Highlight Hot Areas” is Option>Shift>H. Once activated, you will see a red mask over areas that are off the map so to speak, clipped on the histogram and won’t reproduce with any detail.
Image masked with red indicating “Hot Spots” where there is highlight clipping.
With minor clipping, the Highlights Slider alone can bring back detail to the hot areas, and you will see the red masked areas disappear as you move the slider to the right.
For more severe clipping, a combination of reducing the exposure with the exposure slider and highlight recovery slider can do magic. You may have to play with brightness and contrast to get the image looking like you want, but in the end, like the superhero you are, you can save the highlights and save the day.
After Adjustments Pie Boy. Copyright Steve Simon
There is no such thing as an ideal histogram since every image is different and high Key (mostly light toned) and Low Key (mostly dark toned) images will have histograms weighted to one side, but if you can avoid clipping to retain detail, it’s often a good thing. This histogram shows no clipping.