Megapixel myth, image quality & stuff
OK, so lots of opinions and uninformed discussions here. Please allow me to try explain this stuff: (no, I'm no expert. Just read a lot off stuff online
)
- Why is mega pixel important? Well, digital imaging is sampling. Put it simply, it's the process of converting the analog stuff into digital data. The more mega pixel there are, more detail we can have.(higher rate of sampling) However
detail/resolving power is only ONE of many factors that determine image quality. We'll get to it later.
- How many mega pixels? It depends on various factors, but first,
the most limiting factor is the resolution of the output device - i.e. the display. Once you have enough mega pixels to fill the display, then more mega pixel is really only wasted unless you plan to manipulate images or zoom in to see further detail. On a related note, yes, 12 mega pixels and 5 mega pixels don't make a lick of difference unless you zoom in or print large, assuming everything else is the same(a big assumption). More on this later.
- Then the iPod Touch's camera is as good as it gets for the iPod screen right? Well, not quite. Theoretically it has enough pixels to fill up the "Retina" display but the actual resolving power/detail isn't really good enough to fully use the screen. To be more precise, most modern digital cameras use something called "Bayer interpolation" to make up the images from the sensors. It's a nice efficient process for colors but has a side effect of "losing" some detail. In other words, 10 mega pixel pictures don't really have full theoretical details you'd expect from 10 million pixels. So to get the "true" 0.7 mega pixel worth of sharp detail, you have to take a larger mega pixel picture and downsize it. But more importantly...
- Other factors that determine the image quality: dynamic range, noise, color accuracy, etc. Dynamic range is the range between the extreme brightness and the extreme darkness the camera can capture. This is what allows you to get a nice picture with a blue sky instead of a white hole. Remember Apple's HDR demonstration? That's an attempt to increase the dynamic range through software processing. Noise is the "dirty" speckles you see in the pictures.
- How do you improve dynamic range and noise? Two ways:
larger sensor and
better technology. Most times you only see mega pixel numbers and don't see the size of the sensor, but the size of the sensor in the camera is probably the single most important determiner of image quality outside optics and image processing. There's simply no way to get around the law of physics. Larger sensor = more photons collected = better image quality. However technology used in the sensor to catch photons more efficiently with less electric noise is obviously very important too, and many latest smallers sensors do better than old larger sensors because of newer technology. If you wondered why your 12 mega pixel cameras take better pictures than your old 2 mega pixel camera, the newer sensor technology + improved image processing is the answer, not the pixel count. (unless you print large that is)
- No autofocus. Without autofocus, the iPod Touch camera relies on a deeep depth of field to get everything in focus(so to speak). This is OK for video but doesn't really give you that sharp image for photos, especially close shots.
So the problem with the iPod Touch camera is simple: it lacks autofocus, the sensor is too small(bad noise and DR), and the native resolution (720p) isn't really large enough to take full advantage of the screen resolution. The iPhone takes better pictures because it has all those things with a larger sensor.(1/3.2" for the iPhone vs I believe 1/4.5" for the iPod) A larger sensor obviously would mean a thicker body but I personally would welcome it. However it will mean the iPod with a larger sensor will cost more too. Would you be willing to pay for it?
