How to make sure the UIView -drawRect: is drawing with contentScaleFactor of 1.0f?

Question

I've implemented -drawRect: to draw something, and I don't want that this drawing happens on a larger bitmap on the retina display. How can I make sure that this bitmap is always exactly the same across all devices?

I tried to set self.contentScaleFactor = 1.0f; in the initialzier but that didn't help. The system seems to change this back to 2.0f automatically... In my NSLog I keep getting

contentScaleFactor = 2.0f

How to make sure it's 1.0f?