DirtFarmer wrote:
As far as the ISO numbers are concerned, they are usually increasing by factors of 2 (with some numbers in between steps) so you have 100, 125, 160, 200...400...800...1600 and so forth. When you get to higher numbers they are still labelled by powers of two, so you get to 3200...6400...12800...25600...51200...102400
There is no real reason to specify these numbers to more than 1 or 2 significant figures. I think that above 6400 you could call them 12K, 25K, 50K, 100K, without any real confusion. The numbers represent an amplification of the signal from the sensor, and I would bee surprised if the accuracy of the amplification is better than maybe 5-10%. After all, these are pretty much mass produced items.
If you refer to the Hi-5 level on the D6 as 3 million, it's not going to be significantly different from 3,276,800 practically speaking.
As far as the ISO numbers are concerned, they are ... (
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It’s a factor af two because that’s what each full stop is, whether it’s aperture, shutter speed or ISO.