For anyone studying photography out there, what was the process you used to combine exposures? How did you make your selections?
The actual editing process is very simple. I used an app called Image Blender to make the composites (almost always a direct 1:1 correspondence with no masking or tweaking), and then applied Instagram's filters. The selection was the hard part—I probably scrapped 10 or so versions of each double exposure before arriving at the final product. It takes a delicate balance to create an image with the right spatial distribution and influences from both cities. Fortunately, London's perpetually gray skies work really well in double exposures!
Why did you choose to work with a smartphone instead of a traditional film camera or a DSLR? Did anything significantly better or worse happen with your project as a result of your decision to use a smartphone?
I've recently fallen in love with iPhone photography. Many of the images for New York + London were taken while I was also carrying my 5D, but there's something very informal and undemanding about smartphones. You don't draw any attention to yourself when you hold up an iPhone, whereas a pro DSLR definitely elicits stares, or worse, people hurry to get out of your way. The iPhone makes casual street photography a little more natural. The only real downside is that these images are a lower resolution than photos produced by an SLR, so they can't be printed as large as I'd like.