Mark, Be careful with exposure when using filters on cloudy days. Since the light on an overcast day is much bluer in quality than on sunny days, the filter factor for all blue-eliminating filters will be increased. This includes yellow, orange, green and red filters. The opposite happens with blue and cyan filters. I use a Zone VI modified meter and read through most of my filters, which eliminates the problem, but if you apply factors, adjust them for cloudy days. It's better to err on the side of overexposure or bracket if you are not sure.(posted 8068 days ago)Is it worth it? You bet. Yellow to red filters can eliminate a lot of haze (which is mostly scattered blue light), increase contrast between bluer shadows and more brilliantly lit highlights and gratifyingly darken the darker clouds in an overcast sky (which are usually bluer due to the removal of the longer wavelengths by the water vapor in the clouds. The thicker the cloud, the bluer the light). Film is cheap; take one with and one without to see the difference.
Regards, ;^D)