Snapseed has what it calls basic filters and creative filters. The basic filters let you straighten and crop, as well as adjust the brightness, contrast, color saturation, and white balance of your images. Most of these settings are global adjustments, but you can also adjust brightness, color saturation, and contrast locally by using the Selective Adjustment filter.
The following examples run through the filters in the order in which they appear in the Snapseed app, but you shouldn't necessarily use them in that sequence. One of the intriguing things about Snapseed is that it has no set workflow. The filters you use should depend on the photo you're editing and what you want to do with it. Varying the order simply varies the result you obtain, especially with the creative filters. Most photographers will find their own way of doing things in Snapseed, rather than following a set workflow.
All the filters work in the same basic way: Swipe up and down to select a function, and swipe left and right to alter the setting. It doesn't take long to get used to this method, and it's fast, easy, and intuitive. The overlay is always available with instructions, as shown in Figure 3.
Figure 3 The overlay for a filter.
Auto Correct Filter
The clever Auto Correct filter lets you fix any color casts or contrast issues with your images. Snapseed analyses the image to see whether it has a color cast, and how much it can increase the contrast before blowing out highlight or shadow detail. Swipe up and down to move between the two functions (see Figure 4). Both settings are presented on a scale of 0-100. Swipe right to remove the color cast or increase the contrast, swipe left to reduce the amount of change. A zero setting means no change (see Figure 5 and Figure 6).
Figure 4 Swipe up and down to select contrast correction or color correction.
Figure 5 You can adjust color on a scale of 0-100. A setting of 100 applies the full color correction that Snapseed thinks the image needs.
Figure 6 You can also adjust contrast; a setting of 100 represents the highest contrast level that still retains highlight and shadow detail.
Selective Adjust Filter
The Selective Adjust filter allows you to adjust brightness, contrast, and color saturation locally. Start by hitting the Add button (the one with the plus icon) at the bottom of the screen by tapping on the screen to add a control point. Each control point sits at the center of a circle that you can drag around the screen. Use a pinching motion to set the size (see Figure 7); swipe up and down to select brightness, contrast, or color saturation; and swipe side to side to set each one.
Figure 7 Snapseed displays a red overlay to show you the area affected by any changes made with the Selective Adjust filter.
You can add as many control points as you want, adjusting each one individually. I use this handy feature for making backgrounds darker (see Figure 8).
Figure 8 I used the Selective Adjust filter to lighten the girl's coat and darken the background in this image (original top, edited bottom). The control points are marked on the edited photo (the B in the center of each point stands for brightness).
Tune Image Filter
The Tune Image filter is quite straightforward. You use it to adjust brightness, contrast, color saturation, and white balance. The white balance function also lets you turn an image red, green, or blue, as if you had put a colored filter over the lens when you took the photo. The effect is garish on color images, and I'm not really sure when you'd use it.
An interesting function here is Ambience. This slider changes the balance of the light in the image. With an evenly lit image, moving the slider left darkens the background, and moving it right lightens it (see Figure 9). If the subject is backlit, moving the slider to the right increases the amount of light on the subject (see Figure 10).
Figure 9 I used the extreme settings of the Ambience slider here to show its effect on an evenly lit image. You can use it to lighten or darken the background (left to right, the settings for the three images are -100, 0, and 100).
Figure 10 You can also use the Ambience slider to compensate for a backlit subject. Here, moving the slider to the right lightened the darkest tones in the image.
Straighten & Rotate Filter
Use the Straighten & Rotate filter to straighten a crooked horizon by rotating and cropping the image. Snapseed displays a grid to help you judge when the horizon is straight (see Figure 11).
Figure 11 With its helpful grid, the Straighten & Rotate filter makes it easy to nudge the image to the specific horizon you want.
The crop filter lets you crop to commonly used aspect ratios such as square (1:1), micro four-thirds (4:3), or DIN (to match the aspect ratio of an A4 page). Or you can select Free and crop to the dimensions you want-a useful trick if you just need to trim the edge of the image to remove a distraction (see Figure 12).
Figure 12 The Crop filter has six preset aspect ratios you can choose, or you can use the Free option to crop to your preferred dimensions.