What's the maximum reliable length of USB cable that you can use when shooting tethered?
Does it depend on the camera?
There's lots of conflicting information out on the web; I'm hoping Photo-SE can provide some reliable info.
USB 1.1/2.0 specifies a maximum cable length of 5 meters (~16 feet) as a function of a minimum required transmission speeds. That's pushing the limit, to some degree, and will be highly dependent on how well the cable is made, shielding, etc. If you're worried about reliability, I would go under that, probably no more than 3 meters (~10 feet).
USB 3.0 doesn't actually specify a maximum length, but we're still talking copper here generally, and so the maximum practical length is probably around 3 meters to meet the speed requirements, so on USB 3.0, I'd go less than that again, maybe 2 meters (~6.5 feet).
My source for this is Wikipedia which is usually pretty good at explaining standards items. In this regards, I'd probably trust them. In any case, 10 feet is a pretty decent cable length, but if you need much longer, you can also get USB repeaters, bearing in mind that you often get what you pay for with these.
So, in general, I think the limiter is most likely associated with cable quality as opposed to the camera. If the camera is truly specified to the USB 2.0 standard, going with a good cable smaller than the maximum, should be more than fine and use of a good repeater can help in extending that length as you need.
I have 2 12' long active repeater cables and a 6' usb cable I have successfully daisy chained ONE of them from an actively powered USB hub to control my Canon 5Dmk2. As far as I can tell, you can't put a second one on the chain without another power source. I have seen 16' repeaters advertised for ~20USD. So in my successful setup it was:
Mac -- 3' USB cable -- powered hub -- 12' repeater cable -- 6' usb cable -- camera
trying to put both repeater cables in at the same place the first was didn't work, but if you can put another powered hub in place you could probably string quite a distance.
If you need really long distance and don't mind a bit of expense, there's a MUCH better solution: USB over cat5. Example: http://www.amazon.com/IOGear-Ethernet-Extender-GUCE51-Black/dp/B000O2X2OA They say you can get "close to 200'" with that + a cheap cat 5e cable.
A former co-worker uses these (I think that's the model he bought) to operate his telescope, one extends the USB connection on the scope base to his computer, and another extends the USB connection from the computer to the camera he has attached to it. he's using 75' long ethernet cables pulled through a conduit from his basement out to the slab in his backyard where he mounts his telescope.
The issue with the cable length is related to signal quality, some cable will work at lengths greater than 5 meters as previously stated, If you use a hub at the end of the first 5 metre cable the HUB effectively "cleans up" the D+ and D- lines and enables another length of cable to be added. up to 5 hubs can be daisy chained as also previously mentiond! limitations of power only come into the equation if you need the maximum 500mA available from a standard USB port as each hub will consume some of this "power" available. you can use self powered hubs for the first 4 in the chain (without additional usb devices connected) and then use an external PSU for the last externaly powered hub. this then allows the maximum current available at the end of the run! - depending on the type of device used the USB current limitations may not be an issue, general rule of thumb - if the device has its own PSU it wont draw much from the USB host HUB/PC ie a printer, but any thing that can be charged via USB will probably push it over the limit! All "Certified" USB ports must be able to withstand an over current/short circuit condition without any long term failiure. during the USB "enumeration" process the device current demands must be reported to the host and the host must "report" its maximum current available to the device. in the case of apple products USB specs are thrown out of the window, iPad will suck 2.1 amps from a USB port if it can!
In my experience working as a digital operator on pro photoshoots, cables longer than 5m start to have issues 5m is what I and many others I know work to as a maximum without adding repeaters and power boosters etc
Obviously buy the best quality cable you can afford it will help and try not to go over 5m If you are looking at longer cables maybe you need to look at moving your camera closer instead
I bought a cheap £3.5 1.8m "Superspeed USB 3.0" cable on eBay. They sent me a 3m "Hey, we upgraded you for free" cable. My WD Passport Ultra portable hard drive isn't recognised at all, and my Integral pen drive worked erratically (note that both devices are USB 3.0). After reporting the problem, they sent me another cable, this time 2m (so still not quite I ordered). Originally, both devices worked, but occasionally the hard drive connection drops. So in my experience, the only limit is "anything that works well". If you have a crappy el-cheapo cable like mine, even 2m (6 feet ish) can be too long. Conversely, I assume that if you get a really good quality cable that has been tested and certified, then it's ok whatever the length is! So this time around, I did get what I paid for.
There are USB repeater cords that include a hub in the connector. The obvious application is to put a hub in the middle or periodically, and I had an early (long) USB cable that I think was just that.
Most recently, I got a long cable to use with a webcam, and it probably uses a converter on each end molded into the connector, with whatever non-standard transmission it likes over the wire (but see below).
Monoprice shows a 15′ USB extension cord for $1.95. If it's just a normal passive cord with A-male and A-female ends, how does such a long cable work? ⋯ Looking it up, USB 2.0 provides for a maximum cable length of 5 meters for devices running at Hi Speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. So, that is the longest passive run that you can have without a hub visible as a routing hop. A well-made cable of sufficient gauge and quality can do that.
Since the issue is time limits, a funny long cable that doesn't have lumps along its length could emulate the routing hops in one end so the host knows to expect more time.
“close to 200 feet” could mean 30 meters. That's 6× the maximum run, or 5 hubs. If the 5 tier limit refers to hubs after the root exposed on the computer's backplate (as opposed to counting that as 1), then that's probably right: the gizmo on the A side claims to be a chain of 5 hubs, emulates communication directed at those hubs, transduces the data over a different media (ethernet driver chips are commodity) and forms a packet that makes it look like it came through those five hubs.
So to summarize,
the camera and host computer don't matter, if the camera is a normal USB 2 device and the host implements the full USB standard and doesn't chew up tiers internally. IOW, the host might matter more than the camera. A front-panel USB port might be a hub, using one of the available tiers. A multi-device panel that fits where the floppy drive used to go is probably a hub.
A well-made normal cable can be 15′ long and these can be found cheaper than the shipping cost. That should work no matter what.
The longest you can get, period, with any kind of fancy intermediate stuff is a little under 200′.
The direct way, which might be perfectly usable in the circumstances, is 15′ cables separated by plug-in mains power hubs. A suitable intermediate location might be near a plug, or you can run power extension cords along with the USB cables.
Cameras seem to be adopting a standard USB profile for operating the controls and viewing the display, downloading images, etc. They are still spotty, but it does indicate that normal USB communication is used by the tethering software, or a generic program could be used which indeed uses the USB port through the operating system in a proper manner.
Note that some cameras can be connected via WiFi as well as USB. The DSLRDashboard documents (an old version for Android only) seems to imply that this is also fairly standard (or at least is readily accommodated for each brand by the software) and the feature set of controlling is the same for either method, with the exception of speed.
That brings me to one final note: