When it was first announced that the 3DS was keeping 0.3 Megapixel resolution cameras like the DSi, I, like almost everyone else immediately thought "that sucks". It was a few months later that I actually learned a thing or two about megapixels; in regards to the 3DS, 0.3 Megapixels is over thrice the resolution of the 3DS screen, and that there is such a thing as good and bad at any pixel resolution. I took any opportunity to point this out to anyone who was outright complaining about the camera resolution since they likely knew as little as I had. I was just trying to get the word out that it doesn't immediately mean bad things. A few impressions came out from people that played with 3DSes as some press events and the general term being used was "grainy". "Well, I'll see for myself soon enough" I said.
And I did see for myself. Grainy is an appropriate word. But before we get to that, a bit of an observation about how the 3DS uses the cameras. When I first used the 3DS and it's cameras, I immediately noticed that it simply wasn't capturing a sharp image. I went to the camera application, and it did render the pictures cleaner after you took them, so I just chalked it up to a downgrade in resolution to make the real-time capture faster. I tried out the face-merge feature (hilarious results every time, by the way), and it didn't strike me at the time, but the user's face on the outside camera always came up abnormally large even though I tried to hold the 3DS half-way between the two of us. Through more use I discovered what was actually going on; the image from the outside cameras is permanently zoomed at a software level when it's displayed on-screen, thus it's appears more grainy than the end image really is. It actually makes a ton of sense for the end product. The zoom means that the AR cards can go off camera a ways and the AR does not break. It lets you readjust the 3D focal-point after you take a picture, instead of permanently cropping off the right and left of the image. In the end it makes for a better user experience, and if the 3DS can only capture a video at 0.3 megapixel resolution at an acceptable level with it's current processors, then what's the point of asking for something higher?
I've included some pictures I've procured using the 3DS.
In-game screen from PilotWings Resort's handglider
My cat, in 3D! But this is 2D.....
A picture taken in AR Games
A trail I sometimes run
If there's something in particular you'd like clarified about the cameras, or just something (or an idea) you'd like me to capture with the 3DS camera, let me know in the comments and I'll answer or capture the image to the best of my ability.