forms - How to represent optional fields?

I've read somewhere, that if you have more required fields than optional, best practice is to mark the optional form fields.

However I think that asterisk notation for required fields is a widely known pattern. The form will be used by novice/beginner web users, is the above statement (marking the optionals) still better?

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Update: @Janel: thanks for clarifying my question, I have to practice this language a little bit more, if I'd like to work abroad later :). It's important however that there are much more required fields than optional (if there would be eg. 3 optional and 4 required field, than I'll definitely mark the required ones - but there is 12 required and 5 optional fields on one page of the form)

Answer

Good question. There are two opposing considerations here:

1. 
   

   Marking exceptional fields. You want to highlight the fields that aren't like the others. This way you can mark fewer fields in total and reduce visual noise added by each highlight.

   
   


2. 
   

   Following convention by marking required fields. Since users are used to forms highlighting only the required fields (with an asterisk, for instance), suddenly flipping that model on its head could be counterintuitive.

   
   

I admit this is an interesting challenge. My approach would be to A/B test it and see which leads to better conversion. Forms are one of those bottleneck points where you can do some really accurate testing. I'd be curious to hear the results!