7D and noise

[Tabazan]

Hello to all,


Just come back to a mountain shooting at 3100 meters, , with the 7d.


Weather : sunny with a light fog (i.e. luminous but partly foggy).


My question : all pics have been taken at 320 ISO and they all look kinda noisy (at 100%).


Is is specific to that kind of weather / heights ?


Is it specific to the 7D ?


I didn't make much ISO changes because it seemed to me that 320 was quite good (knowing that I needed speed to shoot fast action)


What did I do wrong ?


Thansk for your advices.

[Sheiky]

Hey


well I can't tell you what you might have done wrong, but I could tell you that ISO 320 gives about the same noise as ISO 400. ISO 320 is called a tweener-iso, aka a fake ISOvalue. The true values are 100, 200, 400, 800, 1600 etc. Whole stops. ISO 320 is nothing more than a picture metered at ISO 400 and underexposed 1/3 of a stop digitally.


This is also why a lot of photographers(including me) turn of the 1/3 steps in ISO values, since they don't really matter anyway.


Jan