My last roll of B+W film was taken at a concert in a park. Shooting up onto the stage forced the inclusion of large amounts of sky that were way, way brighter than the subjects. The exposures were fine due to spot metering. But the pure white sky in the background was dissapointing. So, i'd like to try some black and white filters, most notablty either yello or red. One thing that I noticed though is that looking through the filters it doesnt seem to have much of an effect. I guess my question is more about 'visualization' than use. Why is it that looking through the filter doesnt seem to have much of an effect?