[Note:  In the interest of full disclosure, we must confess that Phil & Otto are sometimes recognized as their alter egos Randy Fredlund and Joe Manico]

Otto: Perfesser, I have a question to challenge that fancy science degree of yours that impoverished your parents.  Why have electronics based "motion imaging" gismos like video cameras been around since the last millennium, while only recently we've had those digital "still imaging" gismos that seem like something reverse-engineered from Area 51

 

Ancient video camera and weight training device

Area 51 refugee KODAK EASHSHARE V705

Phil: Well my unlettered friend, it has to do with light.  There is no limit to the lack of light in the universe.

Otto: Or lack of baloney!  If you don't know the answer, just say so and repay your parents so that they can retire to someplace warm.

Phil: Mom and Dad love both Oscar Mayer and the change of seasons.  Regardless, I'll try to make it simple enough for you to understand.  For years, consumer analog video cameras have captured video at NTSC resolution and recorded those signals on tape.

Otto: N-T-S-C?  Not Too Super Camera?  Nobody Trusts Siamese Cats?  Never Taste Slimy Cooking?

Phil: Or Never The Same Color!  That's an old engineering joke, and a good one.  Actually it stands for National Television System Committee, which was established by the Federal Communications Commission in 1940.  This group was responsible for determining what signal would be broadcast so that our analog TV sets could receive them.  Fascinating signal.  A triumph of engineering!

Otto: Maybe fascinating to pointy-headed Perfessers, but of little interest to the followers of the Simpsons.

Phil: Perhaps you are correct.  But the efforts of television engineers like Vladimir Zworykin and Philo T. Farnsworth have saved you from pressing your ear up to the Victrola to hear Homer shout "Doh!"  You and the masses of Homer wanna-bees care little for them or Georges Valensi's brilliantly backward compatible use of the 3.58 Megahertz carrier to introduce color to the airwaves, yet you are happy to enjoy the donuts..er ah..fruits of their labors.

Otto: Doesn't phase me a bit, pal.  But as usual, you've changed the channel.  We were talking about camcorders.

Phil: Yes, yes, my friend.  Because the NTSC signal was a broadcast signal, its use of bandwidth had to be limited.

Otto: What does the distance from the lead singer to the base player have to do with anything?

Phil:  Bandwidth has everything to do with it, if you want to see them both in good focus.  Though it was analog, the television signal was limited to channels with a specified resolution of 4.2 Megahertz.  Grossly oversimplifying, the digital equivalent of this limit is about 440 by 484 pixels.

Otto: What are you talking about?  Everyone knows that VGA is 640 by 480.

Phil: Slow down, my anachronistic friend.  We're talking about a system created in the 40s, and VGA is an 80's computer standard.

Otto: And why would the computer geeks go to all the trouble of doing something different?

Phil: That's another long story, so suffice to say there were some issues with text and interlace and our old friend flicker.

Otto: Who'da thought those geeks cared about an old movie about a horse?

Phil: Reigning this discussion back in, 440 by 484 comes out to be less than 250,000 pixels.

Otto: 250,000 pixels?  I'd never want a camera with only that many pixels.

Phil: Well, then how about 2 Meg?  That's about how many pixels are in a frame of 1080p HD video.

Otto: Maybe 3 years ago.  No way that would cut it now.  I just bought a beautiful little 12Meg job with digital zoom.  And everything digital is better!

Phil: Not always a good assumption with zoom.  Digital zoom can be useful, but you're really throwing pixels away.

Otto: What?  Throwing pixels away?  You can never have too many pixels.

Phil:  Well, yes, you can, and that's exactly why digital still cameras appeared so much later than video cameras.  Since video only needed 400K pixels to match the TV standard, those pixels could be big and collect a lot of photons.  Or more correctly, the vidicon tubes of yesteryear needed less resolution than a still camera.  Still cameras, like digits on the other hand, need more pixels to create a decent picture, so for the same size sensor, the pixels had to be much smaller.  Correspondingly, their ability to collect photons was much less.  And until recently, it was not possible to create an economical sensor with enough pixels and light sensitivity for decent still imaging.

 

Otto: Wait just an atomically-clocked second, Mr. See-it-all.  Video looks good on my TV.  So why can't I just grab a picture out of a video.

Phil: Good thought, my prehensile friend.  The answer is, "Yes, you can," but you won't like it very much.  In fact, both Sony and Canon brought out cameras that did just that back in the 80s.  They captured a field of analog video and stored it on a two inch floppy disk. But they were not embraced by the marketplace. 

Otto: Were there problems?

Phil: Let's just say that they were a bit ahead of the marketplace - the value they provided for the price was somewhat less than what the customer demanded.  You see, the video system takes full advantage of the fact that our eyes and visual system are very forgiving when viewing a moving image.  So you can get away with a lot of inaccuracies in video that would be objectionable in a still image.  HD helps, but the issue doesn't go away.

Otto: OK, OK.  So you are saying that video pixels are big and there aren't so many of them, but that's OK 'cause motion covers up the need for lots more pixels like in a still camera?  And this is all because of the unlimited lack of light in the universe?

Phil: Yes, brave Photon!  You are enlightened!