I have obtained a box of 8 X 10 Portra which I intend to cut down to 4 X 10 for use in my 4 X 10 camera. I normally use Ektar 100 and am wondering if there is anything I should be aware of when using Portra. Film will be used mainly for landscapes and sea and forest scenes both at sunrise and sunset. Any advice welcomed especially in the area of film speed rating and filters.