Monito wrote:
I really don't need the values between (like 400 and 500). It is easier to adjust the shutter or aperture by a third of a stop.
Sometimes the third stop ISOs are useful, for instance in certain cases using the flash and trying to keep the maximum shutter for flash sync, while keeping the same aperture (for DOF) and balance of ambient / flash the same.
When I took psychology in College the teacher said one common inability in the modern world is the ability to sort or rate concepts in terms of their importance or relevancy to the task at hand. With so much information out there, people often seize on some minor detail and spend hours researching, rationalizing, agonizing, explaining that detail while neglecting that the time could be better spent on another more relevant task.
Great discussion, but after reading this thread and the links, it's not clear to me whether I should change how I choose the ISO (other than avoiding ISO 125, 250, etc.). It would also be odd that Canon would "optimize for" ISO 160 instead of ISO 100 when they know 95% of shots are going to taken at ISO 100, 200, etc., regardless of this thread. :-)
This also reminds me of "Highlight Tone Priority", which effectively raises shadow detail at the cost of DR. I.e., if ISO 100 is the "native" ISO for Canon digital sensors, then using ISO 160, 320, etc. would be similar to giving up some DR to increase the signal-to-noise ratio.
Suresh T wrote:
...It would also be odd that Canon would "optimize for" ISO 160 instead of ISO 100 when they know 95% of shots are going to taken at ISO 100, 200, etc., regardless of this thread. :-)
It might not be -- and probably wasn't -- a deliberate choice by Canon. Rather, testing has revealed that due to the amplifier design, the sensel sizes, etc., ISO 160 (159, actually) yields an almost imperceptably cleaner raw image than the ISO 100 setting on this camera.
Experience has shown that different camera brands -- and even different models in the same brand -- actually yield different exposures when aperture, shutter speed, and ISO settings are the same, so this really shouldn't be a surprise. What each manufacturer calls ISO-this or ISO-that isn't really as standardized as it should be.
