Some Very Nice Pixels
January 24, 2010
Lets say you want to own the ultimate digital camera. You want the image quality to be absolutely state-of-the-art; something that can see even better than the human eye.
You hire yourself some really smart engineers, and you go to work. So, what kind of camera specs do you end up with?
Well, the little gadget I’m referring to is the “Wide Field Camera 3.” It was installed during the Hubble Space Telescope repair mission last May (after a several-year delay, while the Space Shuttle fleet was grounded).
And the specs are kind of interesting. Does it boast a bazillion megapixels? It does not.
The larger of the two detectors, the wideband UVIS, includes 16.8 megapixels (4102 x 4096). Considering that back down here on earth, you can buy a 56 Mp digital back for a mere $30,000, perhaps that’s surprising.
The secret is that each pixel is really, really big: 15 microns wide. That gives each one quite a large area to absorb light; and it allows each pixel to store lots of electrons (for a wide dynamic range from darkest to brightest).
Each UVIS pixel is about 7 or 8 times the area of the ones in your typical consumer DSLR. But compared to mini point & shoots, it’s even more ridiculous. Their teensy pixels are about 1/100th the area.
Anyway, the WFC3 does take pretty nice pictures:
Even when price is no object, remember it is still fiendishly hard to make a large CCD completely free from flaws. Instead of one big chip, WFC3 needed to use two, pushed side-by-side.
And even the chips carefully selected to fly in the UVIS instrument have some pretty obvious scars (er, “prominent local structures”) that must be subtracted out of the final image.
Anyway, if you decide to you can’t live without this ultimate in digital cameras, I do have a couple of cautions:
And even though delivering the camera was a little slow, it wasn’t exactly cheap. You better budget a little more for shipping: 1.1 billion dollars.
At that price, you might as well go back to shooting film.