HerbChong wrote:
10 stops of dynamic range can reference maximum and minimum light levels referenced to some external value or it can merely specify how many steps there are between and arbitrary maximum and minimum. both are valid and seen in engineering literature.
Herb...
Actually, neither would be correct as stated. The last would be as the ratio between an arbitrary maximum and minimum, not the number of steps between them (a stop is a logarithmic value and cannot be used correctly as stated), the first would be as the ratio between maximum or minimum light levels referencing an external value, but as stated neither is correct since they misuse the unit in which they are stated. In all the literature I\'ve run across (which is a fair bit, although generally the unit in question is decibels due to the industry in question, I\'m in IP Networking) there\'s generally a certain assumption of familiarity involved. If there\'s a unit and an arbitrary maximum or minimum than the other maximal/minimal value is in reference to a single arbitrary value in a known unit or the unit is merely designating the separation of the two arbitrary values (IE the arbitrary maximum and minimum are 10 stops apart and thus have 10 stops of dynamic range, not there are 10 steps between the two although the latter may also be true).
Note this is a classic case where Photographers, especially Zone System afficionados, make mistakes. 1 zone is NOT 1 stop. It can be, or it can be a multitude of other values since it is simply 1/10th of the SBR (subject brightness range). Unless you have exactly 10 stops of SBR, a zone is not a stop.
With regards to dynamic range, the maximum and minimum values used to measure it can be completely arbitrary, in fact they effectively are as the ADC implementation has a fixed maximum and minimum value so that it can correctly convert analog values between those two points to meaningful digital values.
Feb 08, 2010 at 01:16 PM
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