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film speed
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DIN
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ISO
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15
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25
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18
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50
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21
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100
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24
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200
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27
|
400
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30
|
800
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|
33
|
1600
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|
36
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3200
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1
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16
|
32
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19
|
64
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22
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125
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F-stop
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| 1 |
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f 1.0
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f 1.4
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f 2
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f 2.8
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f 4
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f 5.6
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f 8
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f 11
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1
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f 1.2
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f 2.4
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f 3.4
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Shutter
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| 1 |
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1/4
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1/8 (x)
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1/15
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1/30
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1/60
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1/125 (x)
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1/250
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|
1/500
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|
|
|
|
| ISO Film speed is determined by the amount of light necessary to produce a minimum density (read that as enough silver buildup) to produce resolvable detail in shadow (0.1) density.
So then, how much silver (read that as density) is built-up when a digital ccd collects light? Maybe how much silicon? Obviously none!
Hence: ISO 100 on one digital camera may not be equal to ISO 100 on a second digital camera, and should be considered a reference value. 200 will be twice as fast but 100 is not necessarily the same on all Digital cameras.
Traditional film VALUES have been adopted by digital camera makers to provide an easy transition for the "old timers".
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ISO values are purely reference values in the digital world, whereas the good old f-stop is still calculated using the same lens diameter to focal length ratio. But there is no guarantee that changing a dial labeled f-stop actually changes an iris opening, it might be adjusting the ccd speed. (This one can be tested by a series of depth of field shots.)
Shutter speed might or might not be calculated the same way. Without actually seeing a mechanical shutter, there is no way to know if the shutter speed changes or if the film speed changes. Either might be capable of stopping action in slower exposure situations.
Take all of this with a grain of salt ... I am not suggesting that all digital cameras use subterfuge in their workings, but most of the exact values specified by traditional cameras may or may not produce identical results with digital cameras as "other" adjustments are possible. As you move up in the various camera lines, toward the digital "SLR" cameras you can be sure that things work pretty much as expected. But at the low end, things may not always work as expected!
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