Validate single fields of a backbone form - validation

Question

I would like to be able to validate single fields at a time in my forms using backbone forms and backbone validation, however I am having problems getting this to work if I put my requirements in the model validation, rather than the schema.
My model is:
class Event extends Backbone.Model
url: ->
'/events' + (if #isNew() then '' else '/' + #id)
validation:
title:
required: true
start_date:
required: true
end_date:
required: true
schema: ->
title:
type: "Text"
start_date:
type: "DateTime"
title: "Start Date"
DateEditor: "DatePicker"
end_date:
type: "DateTime"
title: "End Date"
DateEditor: "DatePicker"
The code in my View that uses these is
class Events extends Backbone.View
...
initialize: ->
#form = new Backbone.Form(model: #model).render()
Backbone.Validation.bind #form;
validateField: (field) ->
#form.on "#{field}:change", (form, fieldEditor) =>
#form.fields[field].validate()
render: ->
...
#validateField for field of #form.fields
...
However, my problem is that it only seems to validate if I move the required: true into the schema like so:
schema: ->
title:
type: "Text"
validators: ["required"]
However I'd rather not do this since, backbone.validation has a broader range of built-in validators which I would like to make use of outside this example.
I've noticed that backbone-forms states
There are 2 levels of validation: schema validators and the regular built-in Backbone model validation. Backbone Forms will run both when either form.commit() or form.validate() are called.
However I'm not sure it's running the regular validation when I validate the individual fields? The reasoning behind wanting to do this is that when a user starts creating an event I do not want to validate fields that they are yet to fill in.
Is there any way I can still validate individual fields without having to move the validation into the schema?
Thanks in advance.
======= UPDATE =======
On looking at the form editors source code for individual fields, the validate function is as so:
validate: function() {
var $el = this.$el,
error = null,
value = this.getValue(),
formValues = this.form ? this.form.getValue() : {},
validators = this.validators,
getValidator = Form.helpers.getValidator;
if (validators) {
//Run through validators until an error is found
_.every(validators, function(validator) {
error = getValidator(validator)(value, formValues);
return error ? false : true;
});
}
return error;
},
It does not appear to use the model validation, so I wonder how I can incorporate this?