Tom Barry wrote: > Interesting article, and something I don't think I've ever properly > considered before. Can anyone explain why you couldn't solve the > problem simply by extra pixel bit depth, maybe in a log scale? The sensor has a fixed range between noise and overload. It may not be sufficient for the desired range. Even eyes have irises (and chemical range controls). > Also, assume you instead are Hollywood and currently starting from film > cameras, getting some extra dynamic range. Is there still extra range > by the time you transfer it to some electronic medium? If so, why? Film has a different transfer characteristic than do electronic cameras, so more range can be compressed into the electronic medium from the film. > And does film have better range in theater film projectors as opposed to > current digital theaters? > That's a very interesting question. The film, itself, has terrific range, but it has been copied from a copy (and maybe more generations before that), each copying stage reducing the range. > And how the heck does the human eye do it? > Mostly with chemicals. That's why you can't see much when you emerge from a cave into bright sunlight but can see fine a little later; it takes some time for the chemical reactions to take place. > My apologies as I see my above post looks something like a freshman exam > question that I guess I should research a bit first. But I think it's > an interesting topic with a likely huge payoff for Hollywood once a > solution is (economically) available. Yes. But consider some more features of film. Suppose you want to shoot the brightest thing imaginable -- something like a thermonuclear explosion. Aim a video camera at it, and either you burn out its sensor or you use so much filtering that you can't see anything after the explosion. Use a film camera, and you might burn out a frame, but the next frame is completely fresh. Now consider resolution. Suppose you shoot something electronically that corresponds to just one pixel on the sensor grid (ignore optical low-pass filtering for the moment). Now shift it or the camera by 1/2 pixel diagonally. What was previously 100% in one pixel is now 25% each in four pixels. That shift can cause an awkward effect. In film, grain is completely randomly distributed, both within a frame and from frame to frame. No fixed-pixel-grid effects are possible. There are many more differences. But electronic cameras are certainly catching up. Go see "Click." It was shot on Panavision's Genesis digital-cinematography camera. TTFN, Mark ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.