Best Configuration for attachment fu (images)

Hello,

Well I’ll like to know which is the best configuration or the most
used (standard) when uploading images via attachment fu (or related).
In particular I’ll like to know which is the best resizing option and
the best “thumbnail” size for large images. This is my current
configuration. When I resize strictly to 640x480 the image loses its
original ratio.

has_attachment :content_type => :image,
:storage => :file_system,
:max_size => 4096.kilobytes,
:resize_to => ‘640x480’,
:thumbnails => { :thumb => ‘32x32’, :medium => ‘96x96’, :large =>
‘320x240’},
:processor => :ImageScience
.

Thanks,

Elías