# ISO mode on DSLRs



## PhotoMoose (Mar 5, 2008)

This might be a silly question but how does the typical DSLR sensor implement different ISO speeds?   Does the sensor actually somehow change sensitivity or is it a simple matter of multiplying the sensor's recorded input values by the ratio of the current ISO speed to the base ISO speed (e.g. 4x when using 4'' on a camera that supports 1'' at its slowest)?


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## Brad Snyder (Mar 5, 2008)

Eric, start with the Wikipedia article here:

http://en.wikipedia.org/wiki/Film_speed

and then Google "Digital ISO".  

There's some very technical stuff, some out of date stuff, some simplistic stuff.  Fundamentally, I believe the answer is yes, increasing Digital ISO is an electronic/mathematical manipulation of the photon count the sensor saw.


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