Stepping up from compact to DSLR: question on low ISO

[IronWing]

Almost all my photos are taken outdoors, and usually at ISO 80 (Southern Arizona sunlight). Reading the specs on the D90 I see that ISO 200 is the lowest standard ISO setting. Should I expect to see color saturation changes at ISO 200 on a DSLR similar to going from ISO 64 film to ISO 200 film or are these apples and oranges?

Also I read that the D90 can be used at ISO 100, sort of, but I haven't seen an explanation of what "sort of" means.

Thanks for any insights.

 

[Deadtrees]

You will get the best IQ using ISO 200 on D90. The downside is that ISO 200 is too high to be used in really light area. In that case, you'll have to step up the aperture or use ISO 100 that'll give you worse DR due to it being software-based ISO. Other option is using ND filter.