Can to_representation() in Django Rest Framework access the normal fields

DRF’s ModelSerializer already has all the logic to handle that. In your case you shouldn’t even need to customize to_representation. If you need to customize it, I would recommend to first call super and then customize the output:

class PersonListSerializer(serializers.ModelSerializer):
    class Meta:
        model = Person
        fields = ('foo', 'bar',)

    def to_representation(self, instance):
        data = super(PersonListSerializer, self).to_representation(instance)
        data.update(...)
        return data

P.S. if you are interested to know how it works, the magic actually does not happen in ModelSerializer.to_representation. As a matter of fact, it does not even implement that method. Its implemented on regular Serializer. All the magic with Django models actually happens in get_fields which calls get_field_names which then considers the Meta.fields parameters…