When I'm walking around in a city it's hard to see the portals because of all the fields. The scanner is also always way too "busy" to find all the portals. I was wondering, is there any way to turn the fields off or down so I can just see the portals?
Unfortunately there isn't a way to achieve that. It's a nice idea, you should communicate it to Niantic.
Here's an idea: I haven't tried it myself, only saw the radar screen on my friend's Note 4 but maybe the grayscale feature in the "ultra power saving mode" of Galaxy S5 and Note 4 could change the outcome in your situation. I'll ask him to try it and post the result here.