What’s the difference between a professional passport picture and going to a “quicky” store?

Oh my… take a wild guess.
 
Now for a US passport, they’re not to tricky.  So even if the picture doesn’t look great, and you hate it, it will work for your passport.  Just that you are stuck with that awful picture for the next 10 years.
 
But immigration and visa photos are a whole different ball game.   You don’t want to mess up these.  Technical shooting and lighting is everything.
 
Here’s the technical aspects of a professional studio that will give you the best passport an immigration photos:

1:  A three light system.  Two front studio lights with modifiers for even facial lighting.  One back light to eliminate background shadows on the backdrop.
2:  Several backgrounds.   White, grey, cream, blue…. every country is different.
3:  High resolution portrait camera.  
4:  Large computer screen.   So we can check everything is good:  no shadows, no teeth showing.  Stuff like that.
5:  Computer.   For precision cropping.  And printing templates for the various countries, to make sure their meet the specs.  
6:  Cutting templates for various sizes.  (Every country is different).
7:  Photographer’s address stamp for stamping photos (as required by some countries, like Canada).