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ISO mode on DSLRs


New Member
Dec 3, 2007
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)?

Brad Snyder

Senior Member
Nov 20, 2007
Port Deposit, Maryland USA
Lightroom Experience
Eric, start with the Wikipedia article here:


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There's some very technical stuff, some out of date stuff, some simplistic stuff.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.