David Kay wrote:- > adding more bits does influence the number of subject >brightness levels in f-stops we can record.
Err ....I don't think so. The chip has a level at which it can no longer record shadow detail and a level at which it can no longer record highlight detail. The difference in these two levels , the dynamic range , is often referred to in f-stops . The range is of course defined by a combination of the physical limitation of the chip and often additionally imposed software limitations ( Noise suppression etc). The higher the bit depth , the more recorded steps there are between the lowest amount of light recordable to the highest amount recordable.Wither higher bit depth , you are not achieving more f-stops , just putting more set graduations between the f-stops.The graduations are the equivalent of click stops as opposed to the constantly variable stops on some large format lenses (These 'click stops' are of course necessary because of the digitisation of an essentiallly analogue scene). I can see your thinking in the maths , but it's another one of those conundrums. Bit depth is not related to f-stops in this way. If the Chip has a dynamic range of two stops and a bit depth of 8 bits , then using your logic there are four bits between each stop. By upping the bit rate , I've now got 8 bits between each stop. I've not increased the dynamic range , but I have smoothed out the digitisation of the image by having more points of reference between stops. Speaking of conundrums, can anybody resolve this one ? If you do a a series of time exposures say 2secs , 3 secs ,4secs then the 2second exposure is logically one less stop than the 4 second exposure (reciprocity ignored ), and the three second exposure is a half stop between the two.If you want to increase the 4 sec exposure by half a stop , then it should be 6 secs . However , by the same logic , if I want to increase the exposure of the 3 sec exposure by a half stop , I end up with an exposure of 4.5 seconds . Similarly , if I do the same with my 6 second exposure I end up with 9seconds , but one stop over 4 secs is 8 seconds ! Regards, Bob Marchant. =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
