I am sure the data recorded is different. I think this is because the analog signal is subject to more gain 'pre-digitisation'(!). I cant think of a tehnical reason, but I am sure that this results in a better/cleaner picture than if you shot at a lower ISO and just lightened it in PS for example. Positive that the techies here will provide the accurate reasons why, and maybe we will understand them. Even if we don't, logic suggests that you would be better off shooting at the ISO you need for correct exposure rather than boosting later - they wouldn't bother with an ISO setting otherwise.
> -----Original Message----- > From: Mark Cassino [mailto:[EMAIL PROTECTED] > Sent: 13 April 2004 18:43 > To: [EMAIL PROTECTED] > Subject: Digital ISO And Raw Files > > > Something for the folks with a more technical bent - > > When the ISO setting is changed on the *ist-D, does that > change the data > recorded in the RAW file by actually changing the sensor > sensitivity, or > does it only affect how the recorded data is processed, post exposure. > > Let's say I'm shooting at 1/250th and f 8 and I shoot one > shot at ISO 200 > and one at ISO 800, and everything - lighitng, subject, etc - > is identical > except the ISO setting. So, exactly the same about of light hits the > sensor. Does this result in two identical files, which are > then processed > differently (due to the different ISO settings) to create effectively > different exposures. Or, would changing the ISO result in a > true change in > sensitivity in the sensor, resulting in two RAW files with > different data > in them? In this case, even though the amount of light > hitting the sensor > is the same, the sensor itself would be more or less > sensitive and record > data differently. > > I hope this makes sense - > > MCC > ----- > > Mark Cassino Photography > > Kalamazoo, MI > http://www.markcassino.com -----
