With more people packing smartphones and mobile hot spots, a camera with Wi-Fi gives you the control, flexibility, and quality of a dedicated camera with the capability to back up to a cloud service, computer, or mobile device while you shoot, or share shots online without offloading to a computer first.
However, while many new point-and-shoots have Wi-Fi built in, fewer dSLRs and mirrorless interchangeable lens cameras (ILC) have wireless connectivity. Also, if you have a camera that's only a year or two old, chances are you're not ready to run out and buy a new one just to add some wireless functionality to your shooting experience.
There are ways to add wireless features to your current camera of choice, though. Some are just for image transfers or for remote control with a smartphone or tablet, while others can do both and more.
Wi-Fi-enabled SD cards
Getting a Wi-Fi-enabled SD card is the easiest way to add some wireless functionality to your camera. Considering you're getting storage and wireless in one card they're reasonably priced. They work with most cameras that use SD cards, and once you have one set up, it's relatively easy to use. However, the initial setup can be tricky, and the cards use your camera's battery for power, so you can expect slightly shorter battery life.
The biggest name in the space is Eyefi, which currently offers two SD card options: Mobi and Pro X2. (If your dSLR uses CompactFlash rather than SD cards, you can try your luck with an adapter.) Most cameras are compatible, but if you have an Eyefi Connected camera (of which there are many) you get extra features such as the capability to turn on and off the Wi-Fi radio, and to select and prioritize which images are transferred.
The Mobi card is the easiest to setup and use: download the Mobi app to an iOS or Android device, put in an activation code that comes with the card, and you're basically done. With the app open you can start taking photos, and the card will connect to the device and start transferring images to it.
You can also use a Mac or Windows desktop application to transfer images directly to a networked computer. The card will only support transfers of JPEGs and video formats supported by your phone or tablet and computer.
The Pro X2, on the other hand, will transfer raw format images to your mobile device; however your device may not be able to save or view them. It can also send them to any folder you want on your computer or public FTP server. For the most part, the rest of the features are the same between the two cards, but you do need to setup the Pro X2 on a computer -- it cannot be done on a mobile device.
After Eyefi, there is Toshiba's FlashAir card, which works a little differently than Eyefi's. Instead of just creating a single connection between the SD card and your mobile device or computer, the FlashAir acts like a hotspot, allowing up to seven wireless connections at once.
One benefit to the FlashAir card is that once a device or computer is connected, you just need to open a browser window to view the photos on the card. Also, a firmware update to the FlashAir II cards enables an Internet pass-through feature, so your mobile device can still connect to a regular Web-connected access point.
The cards won't, however, push your shots to your device: you'll have to select the shot you want and download it from the card to your smartphone or tablet or computer.
You can use this list on Toshiba's site if you want to be sure your camera and the features you're after are available, but the cards are compatible with most cameras.
Beyond those two you have Trek 2000's Flucard (there's one specifically for Pentax cameras that allows you to remotely control your camera with your smartphone) and Transcend's 32GB Wi-Fi SD card. I have no experience with these, but judging by user reviews, they seem a bit hit-and-miss.
One last option here: Monoprice and others sell a microSD-to-SD card Wi-Fi adapter. It seems to work similarly to the FlashAir cards by creating a hotspot that up to five devices can connect to as they would to a regular Wi-Fi network. Then you just point to an address in a browser to see and download images.
You supply your own microSD card (up to 32GB is supported), so you're not stuck with one size. Using an adapter might be a bottleneck for high-speed shooting, but if you just need a simple solution, this might be your best bet (and the cheapest, at less than $40).
Camera manufacturer-specific adapters
There aren't many options when it comes to wireless accessories made by the camera makers themselves. In fact, there are really only a few models from Nikon and Canon.
For Nikon, there's the WU-1a/WU-1b. The tiny dongle pops into the Micro-USB port (or Mini-USB port for the 1b) on your camera, and you turn it on via a menu setting. You can connect to it using your iOS or Android device simply by selecting it from your mobile's Wi-Fi settings.
Using Nikon's Wireless Mobile Adapter Utility app you can view the photos and videos on dSLR or ILC and transfer them to your device. You can also use the app as a remote viewfinder and shutter release.
The adapters retail for $60 (£55, AU$70), though you can find them for less. All they do is send to mobile devices, so if you want to wirelessly transfer shots to a computer you'll need something else. Nikon does have professional solutions for this, but they're closer to $1,000 than $100.
Canon doesn't have a mobile solution like the WU-1a/b, just professional transmitters for the EOS-1D X, 5D Mark III, and 6D. There are transmitters available for older Canon dSLRs, too, but they are all hundreds of dollars. If you don't mind going the DIY route, you can do a Web search for adding Wi-Fi to a Canon dSLR and you'll come up with a few interesting solutions.
Picking up the slack for the camera makers are a few third-party adapters that offer quite a bit of functionality without being ridiculously expensive.
The CamRanger, Weye Feye, and iUSBportCamera are the main options currently available. They work about the same, too, letting you tether a Nikon or Canon dSLR to your iOS or Android phone or tablet, or to a computer.
Connect one of them to the USB port on your camera, turn it on, and you can create an ad-hoc network between it and your mobile device or Mac or Windows computer by selecting them in your wireless network settings.
Once connected, you can use the free iOS or Android app to control your camera's settings, get a live view from the camera (if your camera has live view), tap to focus, and trigger the shutter release.
You can set them to automatically transfer shots to your device, or you can just view what you've captured. The apps also have an intervalometer, bulb mode, HDR bracketing, macro photography, and self-timer controls.
The $300 CamRanger seems a bit more polished compared to my experience with the iUSBportCamera, but the latter is also about $100 less expensive.
The Weye Feye at $250 falls in between the CamRanger and iUSBportCamera, and can essentially do the same things like give you full control over the camera via a mobile device. It, too, works only with Canon and Nikon dSLRs. But, the company announced the Weye Feye S at CES 2014, which will work with dSLRs and ILCs from other manufacturers and lets you wirelessly view and transfer photos and videos between cameras and Android and iOS devices or anything with a Web browser.