How is the spectral sensitivity of these films. Basically, I want to know if I will expect to get gray skys without a filter. I'm really not so familiar with the technical details of films but some films give me gray skys (modern emulsions) and others do not (traditional emulsions) without yellow filter. how does foma compare? I ask because some of my point and shoots do not take filters (atleast not practically). I will test but an informed decision will save me money and time. More importantly, any unfiltered examples?