Rumors regarding the second-generation iPad have been circulating since the release of the first model, and some of the most popular recent speculation relates to cameras. It’s widely assumed that the new iPad will have one camera on the front for FaceTime, and potentially one on the back as well, the latter point seemingly confirmed by iPad 2G cases this morning. Yet there has been considerable ambiguity as to whether, why, and how Apple would implement a rear iPad camera up until this point, so we’re going to discuss the issue and add a little to the speculation here.

Whither A Rear Camera? Prior to October, FaceTime seemed to demand two cameras, as Apple included a camera switch-off feature in both the iPhone 4 and iPod touch 4G, the latter of which needn’t have included a rear camera at all. However, in light of FaceTime’s jump to single-camera Macs in October, it became obvious that Apple thinks “FaceTime” should minimally require “a camera focused on your face,” a microphone, and a speaker, plus the horsepower and battery life to maintain smooth audio and video calls. Beyond that, FaceTime can leverage whatever other related hardware the device happens to otherwise include, but nothing’s mandatory. So the choice of whether to add a rear camera to the iPad would be strictly optional from Apple’s standpoint, at least if adding FaceTime support is the key reason to do so.

Why Do It, Then? Competition is a starting point. Regardless of whether Apple likes to appear above adding features merely for the sake of adding features, an increasing number of rival tablet products are including rear-facing cameras. The rest of the iOS line is another factor. Leaving a rear camera out on the iPad when the iPhone and iPod touch now both have them would surprise and disappoint some people, leading to “wait for 2012” discussions Apple would rather not start. There’s also the issue of practicality. Unlike a Mac, which sits on a desk or lap in positions that make less sense for taking rear pictures, the iPad is held in one’s hands and can easily be positioned for photography. It mightn’t be as ideal for photography as something smaller in some ways, but it could be positive in others.

How Will Apple Do It? One thing that Apple really enjoys doing, particularly when adding a new feature to an established product, is rethinking things that competitors have attempted and gotten wrong. In a highly unusual public blasting of the current crop of Android tablets, Steve Jobs personally criticized the whole lot for trying to use a phone-optimized operating system in what amounts to a bigger shell, without going into specifics as to why that was a bad idea, or why Apple’s approach with the iPad (iOS 3.2) was so different. The rear camera could be a prime example.

If you’ve ever tried taking a picture with an Android tablet (say, Samsung’s Galaxy Tab), you probably have some sense of what Jobs was referring to. Filling the screen of a 7” tablet with the same image that appears on the screen of a 3.5” phone just doesn’t feel right. Part of the problem is the field of view. Another is the quality of the photo. The third involves the disorientingly large previewing of that small, low-resolution image. Apple has a chance to fix all three of these things with the iPad.

The first part of the fix would involve using a lens that lets the iPad capture an even wider picture—something closer to a 28-millimeter equivalent. Picture the iPad in an advertisement looking out at a landscape, snapping a picture, and having the landscape appear on the iPad’s screen looking just like what your eyes were seeing. Or taking a picture of a group of people, then becoming the picture frame for the family photo. It sounds so simple, but with the lens on the back of the Galaxy Tab (or, say, the iPod touch) right now, that’s not happening. The iPhone 4 at roughly 30-millimeters comes the closest in its family (previously 37-millimeter equivalent) to being able to capture a wide angle, but the iPad could go further. Even if it was iPhone 4-like, it would be pretty wide—better than the iPod touch by far.

With the right lens and field of view, the next issue becomes image quality. The iPod touch’s 0.69-Megapixel rear still camera has been pilloried for mediocre image quality and lower resolution than any iPhone ever released. Its 960×720 images look so-so on the iPod touch, so upscaling similar images to the iPad’s current 1024×768 display would look pretty weak, ignoring whatever improvements Apple has planned for the next iPad’s screen. An iPad rear camera will need to be better than what’s in the iPod touch to be at least acceptable, and as rivals are using much higher-specced sensors in their devices, it wouldn’t be crazy to see something similar to the iPhone 4’s 5-Megapixel sensor inside.

Last is the previewing issue, and this one’s tricky. Try and hold the Galaxy Tab up to take a picture and what you see on the screen is a big blown up picture of a narrow area in front of you. It just doesn’t feel right, and Apple has to know this. So it has two choices here: adjust the lens and fill the screen, or use a phone-like lens size and display video in a smaller and thus less disorienting preview window. The former would be really cool without much effort, but the latter would give Apple the chance to add buttons, filters, and other stuff around the edges of the window, including features previously found in iChat.

Previewing becomes especially complex because most of the video that’s going to be displayed on the iPad’s screen over FaceTime is going to come from 640×480 front-mounted iPhone and iPod touch cameras—ones that won’t look so hot filling a big iPad screen in any case. On the Mac, it displays FaceTime videos by default in a small window, but the windowless iPad presents a new challenge. Apple’s going to need to figure out whether to fill the iPad’s higher-resolution screen with blocky upscaled pixels, or do something different. Apple favors consistent interface solutions, so it wouldn’t be a shock if it introduced an across-the-board “live video” interface that doesn’t fill the screen either for FaceTime or Camera applications. Then again, it wouldn’t be surprising if it went full screen for both, or used different approaches because different teams are working on the apps.

Our Predictions. Our best guess at this moment is that the rear camera on the iPad will be bigger, wider-angled, and better in resolution than the one on the iPod touch, with at least one if not two of those factors at least rivaling if not surpassing the iPhone 4. We’d expect new FaceTime and Camera applications for the iPad, the former with a well-considered approach to handling both outgoing and incoming video from the increasing array of FaceTime devices, and the latter with a previewing methodology that makes more sense on tablets than what Android-based rivals have accomplished. And of course, we’re betting that there will be ads that focus on the camera and iPad synergy as creating the first picture frame that actually takes photos worth framing. If Apple pulls off such a feat, which depends on the right lens, sensor, and UI, the next iPad will instantly be even cooler and more social than the first one.

What do you think, readers?