The `image_field` method in `formtastic` generates a file upload field for an image. The generated file input field will use a hidden field for the existing image, and if there is an existing image, a link to the image is created with the ability to remove it. If there is no existing image, a placeholder image can be specified.
The following code sample shows you how to use the `image_field` method:
ruby
f.image_field(:avatar, :label => 'Avatar', :hint => 'Use a 150 x 150px avatar image.')