Per Öfverbeck writes: 24 sep 2008 kl. 21.24 skrev ADavidhazy: > Hi, > > I was given a sample of some photographs taken of the propeller > of an airplane made with, I believe, a phone camera. There is an > obvious anomaly present. Although I suspect the reason I am not > really sure (really I do not know!) how this came about. If you > can shed some light on the effect for me it would be much appreciated. :These observations seem like a dead giveaway that we do have some kind :of scanning effect within the camera itself. Only, the scan isn´t :just sequentially one line at a time like a flatbed scanner; there are :several parallel channels at work simultaneously, spaced a certain :fraction of the image width apart. AFAIK, many CCD devices do work :that way. :When watching a dull TV show next, try waving your hand rapidly in :front of the screen, with fingers spread (works well with an old- :fashioned CRT TV; don´t know about modern flat ones). You´ll be :surprised by the apparent form of your fingers.... ;-) It´s a :similar phenomenon of scanning interference. it's not as noticeable with computer LCD's, but try wiggling your hand in front of them and then in front of an incandescent light for comparison - you'll see even many LCD's do it too .. by design now many (most?) actually introduce a 'flicker' deliberately (flashing a black screen at regular intervals) in an attempt to make game play show less of the blurring seen on early LCD's .. it's one of the many tricks they use to try to make lcd's behave closer to what CRTS do Back to the question - antialiasing, demosaic tricks and algorithms play havoc with moving subjects in the digital world (that's an extreme example Andy!) , more can be found here: http://scien.stanford.edu/class/psych221/projects/98/demosaic/kodak/ Anyone who wants to try can wiggle their camera while photographing a point source light.. occasionally if you hit it right, rather than get the nice long streaks we were used to with film you're quite likely to get repetitious images - and more: http://photo.net/digital-camera-shopping-forum/00CKgJ - also a discussion about a propellor photo, the photo link it's self is no longer there though :/ which poses an interesting thought - it would have been nice to see what images taken at different angles and different orientations of the camera would have produced - this would have given more insight into how that particular camera did its magikery :) another digital prop pics http://www.boingboing.net/IMG00005.jpg k
