The Joy of Pixel Density

Started Jul 13, 2008 | Discussions thread
Joesiv Veteran Member • Posts: 5,497
Re: Thanks John

Brad Nichol wrote:

On the subject of noise a method I often use with compacts under low
light is to take 4 or more identical exposures and blend them in
registration at 50% in photoshop, what is really obvious by this
method is that once you have about 4 images blended together the
shadow noise has pretty much been all cancelled out leaving just the
real picture information, so even with really high MP counts we could
get totally clean results if we needed it for some non moving

Something that confuses me is, if you take 4 exposures, and those are "canceling" each others' noise, why wouldn't you just take a 4 times as long exposure, at a lower ISO? Wouldn't that result in the same performance?

This doesn't seem to have anything to do with pixel density, but rather how much light is usable in shadow areas, or length of exposure. Circumventing sensitivity constraints of the sensor/electronics.

Perhaps it's a limitation with current sensors that saturdation points are reached too early, thus making ISO 25 not possible?
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