This is how to do it:
- For a content type "News" create two image fields, lets say: Foto big and Foto thumbnail,then go to: admin/content/node-type/news/display
- Check excluded for teaser and full node, there will be no display for this field you on will see it in the form.
- Prepare your images in a folder and download: http://thumbnail-generator.en.softonic.com/ it is a free software that will automatically create your thumbnail images for a whole folder.
- Create you content with both images: Foto big and Foto thumbnail
- Create you view with only Foto thumbnail as image.