Ask a photographer...

[Margus]

Don't want to spoil the Q&A thread but IMO: your chain is as strong as the weakest link in it. Chinese filters would do allright with cheap lenses. Yet when you have decent (i.e. fullframe camera and high-end lenses) equipment you'll definitely degrade if not kill the overall quality with cheap filters. Then you'll see how bad those cheap filters really are. Been there done that.

With the digital I wouldn't bother much with less used filters at all (warming, GNDs, etc), especially when shooting RAW. Doing multiple different exposures will do the trick, even most semi-pro cameras have this AE+/- as a built-in function anyways. Glue them thogether as layers later on in post-processing and it'll look like a shot with a graduated filter, not as good as with a decent optical filter, but close enough. Ditto to warming filters - this you can do in PP (Post-Processing). It's cheating allright, but so is most of digital photography anyways since the very limited information coming from CCD/CMOS goes through massive complex in-camera processing engine of mathematical calculations, de-bayering, noise shapings, multiple levels of signal processing and other visual cheating anyway to make it look "real" for a human eye (have you ever seen a direct-Bayer image from CCD/CMOS?). Other than increased pixels the sensors haven't evolved as much as the mathematical processing engines inside the cameras we don't hear much about other than versions/generations (i.e. "Digic V" etc). Lot of people don't know there's a massive "Photoshop" already in-camera without you knowing about, so doing some dramatic Photoshoping later doesn't make much difference in terms of cheating. But the big pro for all this in-camera manipulation and cheating is that the digital RAW is a finely prepared and very flexible and easy to use medium to work with in PP - this and also the digital PP itself has evolved a lot making usage of optical filters less important IMHO.

All IMHO of course,
Margus