Autodesk SketchBook Mobile for iPhone and iPod Touch

Pros:

• Large variety of brushes and brush options, including an eraser and flood fill.
• Symmetric mode, offset painting mode, simulated pressure.
• Six layers, canvas size up to 1024 x 682, zoom from 20% to 2500%.
• Export layered PSD files and send by email for further processing in Photoshop.
• Detailed in-app help, and a brief tutorial for new users.

Cons:

• Performance lags. It is recommended to exit the app about every hour to improve performance.
• Has some limitations if you don't have the latest iPhone and iPod touch hardware.
• Maximum image size is 1024 x 682 (on 3GS/3rd Gen hardware). No exporter for higher resolution.
• Layers editor could be more intuitive, and doesn't offer a merged view of your drawing.
• Changing brush size/opacity and working with layer transformations was difficult for me.

Description:

• Work with 25 brush variations (including an eraser) and adjust brush radius, opacity, spacing, and hardness.

• Choose colors from color wheel, RGB sliders, swatches, or eyedropper. Eyedropper is offset for accuracy.

• Large zoom range (from 20% to 2500%).

• Export drawings and send by email as flattened PNG or layered PSD files. Duplicate drawings.

• Layers: Up to 6 on iPhone 3GS/3rd Gen. iPod, 3 layers on older hardware.

• Layers can be duplicated, merged, hidden, re-ordered, and adjusted for opacity.

• Layer transformations include move, rotate, and scaling.

• Canvas size: 1024x682 on iPhone 3GS/3rd Gen. iPod, 600x400 on older hardware.

• Undo/Redo: 20 operations on iPhone 3GS/3rd Gen. iPod, 10 operations on older hardware.

• Sketchbook Mobile has a dedicated Flickr group for sharing and browsing thousands of artists' images created in SketchBook Mobile.

• SketchBook Mobile is regularly priced at US$2.99 from the iTunes App Store. SketchBook Mobile Express is free with limited features.

Guide Review:

SketchBook Mobile offers a generous 25 brush variations to work with. Among these are flood fill, eraser, airbrush, pencil, and many textured brushes. The brush editor lets you choose the hardness of your brush from 3 settings--soft, solid, and hard. In addition, you can adjust the brush radius min/max, opacity min/max, and spacing. A preview of the brush stroke is provided above the brush editor sliders.

By offering min/max sliders for opacity and radius, SketchBook Mobile allows a simulated pressure effect with strokes that vary in opacity and thickness. This can help you create some unusual painting effects. Another unique feature of Sketchbook Mobile is the symmetric mode, in which your paint strokes on one half of the screen are mirrored on the other half.

SketchBook Mobile's tools (aka "marking menu") are invoked by tapping a small icon which is always visible on the screen. Dragging over the icon while painting does not invoke the menu. This method ensures the menu doesn't pop up unexpectedly. There is an optional feature which enables double-tap gestures in the four corners for clear layer, zoom to fill screen, undo and redo. Several times I accidentally cleared my layer when painting in the corner, so it's good that this is an optional feature.

Sketches are saved to the gallery, and you can import images from your device's photo library, export to your photo library, email a flattened PNG, or email a layered PSD file--all in the gallery.

Layered PSD files can be opened in Photoshop (or other software that supports PSD) for further processing. Although Sketchbook Mobile does not have a desktop application for exporting your drawings at higher resolutions, I found that standard resampling methods within Photoshop did an acceptable job of increasing resolution. It helps that SketchBook's native image size is larger than most other apps.

I did experience some lag--my brush strokes dragged behind my finger at times--but this was only a mild annoyance. Autodesk recommends exiting the app and reopening it about once every hour for optimal performance.

I also found some of SketchBook's gesture-based controls a bit frustrating to work with: adjusting brush size and opacity with the marking menu puck, and the two-finger gestures used for layer transformations. With the puck, you tap and drag up or down to adjust brush transparency, or drag left and right to adjust size. I found it very difficult to get it to do the one I wanted. The two-finger layer transformation gestures are awkward and difficult to control. And if you're not very careful, the program will chop off the parts of the layer that move outside the canvas as you're moving and scaling it.

Another area where I feel the program could be improved is the layer editor. I had to consult the in-app help to understand some of the icons; and the interface is rather plain compared to the rest of the app.

But these issues didn't detract terribly from my enjoyment of the app. Without a doubt, SketchBook Mobile is one of the most flexible painting and drawing apps for the iPhone and iPod touch and it truly showcases the power of the platform. If I had to limit myself to just one creative app for iPhone or iPod touch, it would be Sketchbook Mobile.