Archived posting to the Leica Users Group, 2006/09/20
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>http://www.luminous-landscape.com/tutorials/expose-right.shtml > A 12 bit image is capable of recording 4,096 (2^12) discrete tonal > values. One would think that therefore each F/Stop of the 5 stop range > would be able to record some 850 (4096 / 5) of these steps. But, alas, > this is not the case. The way that it really works is that the first > (brightest) stop's worth of data contains 2048 of these steps ? > fully half of those available. Even if we assume that the brightest stop (blinding white vs. temporary loss of vision white) contains 2048 discrete tones, if we don't record these, we're not throwing away half the information. The human eye can't ascertain 2048 distinct tones within the brightest stop. Heck, 256 tones from black-cat-in-a-coal-mine to polar-bear-in-bright-sunshine are enough for us to perceive as being continuous without interruption. So to claim that we're throwing away half the bits if we don't have the very highest stop is a bit misleading, at best. I enjoy reading Reichmann's articles, and looking at his pictures. He appears to be a very competent photographer. But just because he knows how to make a photograph doesn't necessarily translate into his being correct when it comes to all things digital. (Maybe he is correct. I have a feeling that he isn't entirely wrong, but I believe that saying half the information is in the brightest stop is misleading, at best.) If half the information is in the brightest stop, wouldn't it follow that if we remove that one stop, our file sizes would drop by 50%? After all, if you remove half the information, there's only half as much remaining to store. -- Eric http://canid.com/