Since it keeps coming up I figured I would just create a new topic on the subject to put all my answers in one place.
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Ad-hoc doesn't work on the current iOSs enough to be reliable. Period. If this is how you make money then you need the reliability of "mobile hotspot".
Ad-Hoc is a "peer to peer network" what that means is that your device(camera, wifi card, WT, etc.) is talking directly to the receiver. The receiver is where the pictures are going, be it an iPhone, iPad, computer, etc.)
A "mobile hotspot" is a small battery powered router, usually with the capability to access a cellular data connection (not needed for in the field use, more bellow) that creates a wireless network that you can put both the transmitter of the photos and the receiver of the photos.
In my opinion using a "mobile hotspot" (as defined above) is the only way to even come close to the reliability of shooting tethered in a studio. If you have power than you can even use a home router. Internet is t required to get the photos to ShutterSnich, only if you want to post them somewhere else (Facebook, FTP, Dropbox, etc.) so don't worry about an Internet connection. The device that you use to transmit (Eye-Fi, Transend, WT, built in wifi, etc.) doesn't matter. They will all function more reliably with the stable network of a router, mobile or not.
So then these questions usually come up:
Which "mobile hotspot" should I buy?
Easy. The cheapest. Mobile upload speeds mean nothing if you aren't gonna use it. I try to find MiFi (brand name) just because I know the interface, and I buy 3G (out dated technology) and look for ones from out of business carriers(not Sprint or T-Mobile, company's that are long gone) since they are super cheap.
NOTE: My iPad (my reciever) has the option to add a month of Internet to it at anytime that I need it. When I had an iPad that didn't have that option then I bought mobile hotspots from pre-paid cell companies. That way if a job needed me to be posting "live" from location I could pay for that one month of data. The rest of the time I didn't have to and it could wait till I got home.
What home router?
Anyone that will run DD-WRT. I prefer Linksys referbuished but that's because I get them cheap and they are worth it. A $5 used E-Bay router with DD-WRT will out run most $200 commercial routers. HOWEVER if you run DD-WRT there is no support for it here or the manufature of your router's website. That is advanced stuff handled on their website, but we will help you there.
No this is not the setup everyone needs, nor what would work best for everyone. This is just my recommendations on a reliable, in the field setup. I tried to hold my personal preferences out of it (only one brand of camera touches my hands) but I wanted to post what has worked so well for me and many others since this seems to come up a bit and it's not always appropriate to dump all this in a troubleshooting thread.
Any questions ask.
-MDJ