GND is used to reduce the Dynamic Range (DR) of a scene....after you get the smaller DR, it is still up to you where (as in the highlight or shadow, not foreground or background) you want to meter for the mood of your pic....to be safe, meter the mid tone item. Or meter the brightest highlight and the darkest shadow, then calculate the middle for a safe exposure.....thats how I do.
( unfortunately all the talk, but i dun have an array of GND to cater for all the various differences , so it is at best a guesstimate )
Landscape with my wide angle lens, i go down to the range of f8-11 if i want to keep everything in sharpness. There is this nagging thing about stopping down too much and get diffraction effects . I never really pixel peep and compare but for all means and purposes f11 is ok for me.
Aperture size really depends on what you are shooting and what you wanna achieve?
You know, I have no real idea what you are asking, and I don't mean any offense, no idea how to put it any other way; first you ask about metering, then you ask about aperture and shutter speed. What are you asking?
Aperture and shutter speed have NOTHING to do with GNDs, the only link I can think of is how stopping down more (i.e. using a larger f number) might reduce vignetting from the usage of GND on certain lenses.
PP's can save you money and can even enhance your creativity and skill but there special filters that can be quite hard to emulate in PP's. (e.g. Polarizer)
Heyo, someone mentioned that UV filters aren't very useful in Singapore. Is that true? How does it reduce image quality, though? 'coz I'm not entirely sure how UV actually degrades image quality in the first place.
As to the degradation, IMHO it is best not to put any extra un-needed glass in front of your lens. I used to have a few NC filters for the sole purpose of protecting my lenses, but after a while I have removed my NC filters off my lenses, and be extra careful with my stuffs. ( Maybe until something happens .. )
Eh, well, I really protect even my UV filter, so I don't think it's really an issue. I can't actually see a quality difference before and after the filter, so that's why I was asking. I know some really picky photographers swear that the UV filter "degrades" their images, but I think that kinda degradation is probably detectable only with computer analysis and is probably not significant for use even in competitions (unless those also use computer analysis =p)