I have a view that looks like this:

And I display a pop up window like this:

Every transition I try looks like a cheap hack. Apple has a similar white pop up window in their app store that sort of bounces open like an alert view then the background fades a little bit.
How can I achieve this effect?
Right now I just blur it in like this:
[previewView setAlpha:0.0];
[[self.view.window.subviews objectAtIndex:0] addSubview:previewView];
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:1];
[previewView setAlpha:1.0];
[UIView commitAnimations];
and it looks terrible.
I don’t really care what the animation is. I just want it to look professional.
See my answer.
FTUtils has a pop-in animation that does exactly as you describe.
You use it with a single line too:
Or pop out: