How to reference a view using entity reference field type? I have two content types, courses and tutors.
Tutors contains a biography and a large photo

Courses contains lots of other information but more importantly contains a tutor field which is a entity reference field type.  It creates a dropdown list containing all tutors.

The problem I have is that when I create a new course page and select a tutor from the dropdown list, it displays the full biography and large photo. 

What I want it to display is the first say 100 characters of the biography and a cropped version of the tutor photo (I have set up a image style which crops the photo to 100px)

I’m guessing there may be 2 ways of doing this.
1)  Customising a teaser 
2)  Creating a view but I’m not sure how you reference it and how you would get the view to just show the selected tutor (from the dropdown list above)

I am using Drupal 7

Any advice much appreciated.
Sounds like you know what your doing. Like you say either create a 'view mode' in your content type or create a view. All you have to do with the view is create a relationship (under 'relationships' in the advanced section) to get your entity reference and set a filter for the tutor.

Tried to find something similar to your issue, hope it helps. How to use Entity Reference and Views