iPhoto Adjustments - Levels
This article represents the first in a series where I will cover the image adjustment features of iPhoto. Many users do not make full use of the adjustments offered by iPhoto. With iPhoto 08, Apple has introduced image adjustments that were usually only previously found in professional image editing applications.
To display the image adjustments HUD (Head’s Up Display) in iPhoto, either of the following will work.
- Select a photo in the browser and click the ‘Edit’ button in the toolbar at the bottom, or
- Double click a photo in the browser and then select the ‘Edit’ button in the toolbar at the bottom
Levels
The Levels adjustment is displayed as an RGB (Red, Green, Blue) graph at the top of the adjustments HUD. Three sliders are provided underneath the graph that control the various tone levels of the image, the Lows, the Mids and the Highs. More advanced applications such as Aperture allow finer-grained control of each color channel; however, iPhoto only operates across all three channels at once. For most adjustments this restriction is perfectly fine.
To demonstrate the effects that the Levels adjustment has on a photo, we will be using the following photo of the Sydney Opera House with a couple of passing Sydney Ferries. The image Adjustment HUD is shown to the right. Adjustments can be made in either windowed or full-screen mode.
Each color is represented in a value between 0 and 255, and are represented on the graphs scale as between 1 and 100%.
Low Level Adjustment
By adjusting the lower slider, you are in fact setting the lower limit of the graph.
Adjusting the lower slider to 25% effectively ‘chops’ the color information below the 25% mark, reseting the 0% mark. The image darkens to reflect the adjustment.
Note that by chopping the color information you are actually removing detail from the photo. iPhoto is replacing the lost detail with black. To ensure that you do not remove much (if any) of the tonal detail from the photo, you should not move the slider past the start of the color information, or where the RGB graph starts to rise. In the example image, I have removed a lot of the darker image detail.
High Level Adjustment
Similar to the low level adjustment, by adjusting the higher slider, you are setting the higher limit of the graph.
Adjusting the higher slider to 75% effectively ‘chops’ the color information above the 75% mark, reseting the 100% mark. The image lightens to reflect the adjustment.
As with the low level adjustment, by chopping the color information you are actually removing tonal detail from the photo. In this case, iPhoto is replacing the lost detail with white. In the example image, I have removed some of the lighter image detail.
Mid Level Adjustment
The mid level adjustment is typically used to achieve a balance between the shadow and brightness levels of the image. Also, after adjusting the low and high levels, you will usually need to adjust the mid level to re-balance the photo.
Adjusting the mid level slider towards the lower end will adjust the ratio of darkness/lightness biased towards the darkness end. Therefore, the image will lighten, as the darkness range is reduced.
Adjusting the mid level slider towards the higher end will adjust the ratio of darkness/lightness biased towards the lightness end. Therefore, the image will darken, as the lightness range is reduced.
Summary
Levels adjustment might seem a little strange at first, and I recommend you take some time to practice with the various sliders and the changes they can make to a photo. On photos that are not very well balanced (such as very dark or very light images), adjusting the levels can make a dramatic change to an images tonality.
As with all adjustments in iPhoto, it is possible to reset the changes if you over adjust an image. If the ‘Edit’ -> ‘Undo’ option will not undo all of the changes, you can revert the image to its original using the ‘Photos’ -> ‘Revert to Original’ option. When using RAW images, the ‘Photos’ -> ‘Reprocess RAW’ option should be used.
Levels can be a powerful and effective way of making adjustments to your photos. In subsequent articles, I will cover the other available image adjustment features of iPhoto.
Tags: iPhoto, Photo Adjustment
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