Before I leave the house, I check my pockets for two things: my wallet and the iPhone. It's at the top of my essential gear list for nimble photography. In fact, I can't imagine my work without it.

But not for the same reasons as many others.

When you're the type of shooter that I am - always working with new gear ranging from the latest digital to decades-old analog - I need a constant that I can depend on. The smartphone is the one tool that works with everything else. Here are five top of mind examples.

Snapshot Camera - Yes, I'm starting with the most obvious. But the ability to never miss a moment is huge to me. For decades, I've always wanted a camera that would be my constant companion, and the iPhone 6S is exactly that.

Mirrorless Conduit - I love mirrorless gear for event coverage, whether it's being a spectator at an NBA game or working as a festival photographer. Generally I shoot RAW+Jpeg, allowing me to transfer files from the camera to the iPhone, then publish them online while still on location. Whether I'm using WiFi or the Lightning card reader, the iPhone is my conduit from professional camera to the online world.

Personal Backup - The minute I copy an image from the mirrorless, or capture it with the phone itself, those images are automatically backed up to iCloud and Flickr. I don't have to think about it. I don't have to push a button. It just happens. That means I will never lose those shots.

Competent Light Meter - I was shooting with a Pentax ME Super this morning and the light meter decided not to work. This happens with older cameras. No problem. I used the 1/125th mechanical shutter option on the ME, pulled out my iPhone, and launched ProCamera. I set the app to ISO 200 and took a meter reading. Those are the settings that I used for the Pentax, and I kept on shooting. I'm sure the shots will be terrific.

Metadata Tracker - I keep a photo journal with the Day One app. So when I shoot a film or digial shot, I grab a quick iPhone image too that also records weather and location. Plus I can add my own notes and comments. I cannot express how helpful these journal entries have been toward helping understand my photography and improving it.

All of this without even discussing image editing or swiping through Instagram shots while standing in the grocery checkout line.

A competent smartphone has the highest of nimbleosity ratings. And it's the parachute that has saved me so many times.

-Derrick