"Someday, smartphone cameras will be just as good as DSLRs!"
No. That is marketing speak. And while industrious photographers have taken some amazing shots with smartphone cameras, their achievements will always represent the exception, not the rule. Still, not everyone's going to lug a DSLR to their family gathering. A smartphone may be your only option.
You also can't just rely on someone else capturing memorable moments. Believe it or not, some may be interested in turkey, football, or something weird like spending time with loved ones. So if you've got that photo album mentality, don't let this be another year of missed photo-ops where your smartphone's automatic settings produced an automatically terrible photo. Here are some of the most dangerous perils of smartphone photography, and how to work around them in a pinch.
Tricky White Balance
White balance, or color balance, defines what your camera considers "white," and therefore affects the color cast of your entire shot. If you've ever had a photo come out orange, that's bad white balance. While cameras and smartphones can usually do a good enough job outdoors, the warm glow of incandescent light bulbs is going to throw any camera for a loop.
Sure, there are times when the welcoming glow of indoor light is going to look great, giving you the warm and fuzzies. Other times, it's going to look like Uncle Rich got a spray tan. If he did, that's wonderful. More power to him. If not? He'd probably like to not have relatives wondering why he looked like an Oompa Loompa back in 2013.
So how do you get around indoor lighting? You advanced shooters out there can capture RAW photos (which let you set white balance later) or take a custom white balance on the spot. Everyone else can usually get a good enough result by finding the camera's white balance presets and setting it to the "Incandescent" or "Tungsten" option. The symbol for this usually looks like a light bulb, making it pretty easy to find.
Flash + Food = Bad
Flash is generally considered a poor choice for food photography illumination, and while I've had the privilege of working with some excellent food photographers that did use flash, their setup was a bit more complicated than "my phone's LED I otherwise only use when the power goes out." Even with a real camera, the harsh on-board flash will give your food an unappetizing, artificial look (and it won't do much better for human subjects either).
Since one can hardly be expected to carry diffusers and reflectors to Thanksgiving dinner, you're going to need to work without flash. Unfortunately, smartphone sensors are woefully unprepared for low- or even medium-light situations, which will lead to plenty of lost detail. Again, even nicer point-and-shoots will perform far better.
There's no easy fix for this one, but try to seek whatever additional light is available. Turn on some extra lamps, move to an area that's more brightly lit, or outside if the weather permits. The more natural-looking light you can get, the better, especially for any photos you may actually want to get printed. One thing you absolutely want to avoid is relying on filters and modes like "HDR" because...
HDR Rarely Works Out
If "HDR" is one of those settings you've seen in your smartphone, but couldn't figure out what it's used for, here's the deal. HDR or "High Dynamic Range" photography causes the camera to shoot three photos in a row: one that's a little too bright, one that's a little too dark, and one that's just right. The software then combines only the properly exposed parts of the three shots to create—in theory—one shot that's perfectly exposed throughout.
Problem is, HDR is designed to be a subtle technique primarily for landscapes. Your family is not a landscape, and the filter-laden app you're likely shooting with is about as subtle as an ugly Christmas sweater.
Use HDR if you want to, but choose your shots wisely. HDR can be nice in some situations, but HDR will rarely rescue a shot that your smartphone wouldn't have done a fine job with anyway. Watch out for motion too. Remember we're combining three shots, so if your subjects shift position midway through, it'll cause a blur.
While we're at it, let's just throw out the whole suite of Instagram filters. Sure, they make your Venti Machi-whatever look fancier than just coffee in a cardboard sleeve, but nobody really cares. For family portraits, they're even worse. There's no reason to make your in-laws look like they were photographed with a Soviet-Era film camera. It's not the 70s anymore. The wall came down. Billy Joel sang a song about it. Sure, we're not all driving hovercars and taking monorails to work, but we're also not wearing polyester everything anymore. Embrace the future.
Depth of Field
Bokeh—the flattering background blur found in good photos of food and people—is often the quality that first-time DSLR owners make the jump for. The presence of bokeh is a function of three in-camera factors: sensor size, aperture setting, and focal length (a.k.a. optical zoom, digital zoom doesn't count). Smartphones are terrible at all three. They're equipped with tiny sensors, filters in place of apertures, and fixed focal length lenses; meaning they're wholly unable to produce flattering, defocused backgrounds.
Even a cheap point and shoot camera would be better at creating bokeh than a smartphone, because at least then we could recommend zooming in your camera but backing up yourself, which would separate your subject from the background and create at least a modicum of blur. But, and please correct us in the comments if we're wrong, as far as we know the only smartphone with any optical zoom at all is Samsung's new GALAXY S4 Zoom. There are apps out there that will draw fake bokeh on top of your photo, but they aren't very convincing, and then you're stuck messing around on your phone during Thanksgiving, which is really the worst mistake of all....
You're on Your Phone
The "anti-social factor" is sort of the be-all, end-all of most smartphone vs. anything discussions. And you know what? We think the social faux pas probably won't even be worth the effort.
Ignoring the fact that you're puttering around on a phone while arguably the most important family holiday takes place around you, all this lowest-common-denominator Thanksgiving smartphone photography just isn't worth your time! Think about the albums you click through on Facebook, you do so because those people are doing something unique and interesting, like that time your cousin went skydiving. Thanksgiving happens at the same time, on the same day, for everyone in your social circle.
Put down the smartphone. In fact, consider just putting down cameras altogether, or set aside 10 minutes for "picture time." But if you choose to ignore our advice, please, make sure most of your subjects are people. In twenty years, you're not going to care about how perfectly set the table was, you're going to miss the people. Photograph them well.