I just bought the Lee 4 X 4 filter holder kit. For now, I will fit it onto an 18-55mm lens. Do I need to get a standard 58mm adaptor or the wide angle 58mm adaptor?
Correcton, 18-55mm lens has a 52mm filter size. Not 58 as mentioned above.
The standard adapter may vignette on at 18mm range. It is hard to say, though
I had a wide angle lens with 67mm outer dia and the standard 67mm adapter vignetted on it badly, so I got the wide angle adapter.
Depends on the camera. If using a full frame camera then anything wider than 24mm wide angle lens needs the W/A adapter ring. With less than full frame cameras need to take into account how much cropping there is. May get away with standard adapter if not a full frame camera at 18mm. I use only W/A adapters so I don' t ever worry about it. No disadvantage other than cost. I only shoot full frame so why take a chance?
If you purchase the standard adapter, there is a good possibility that it will vignette at 18mm. The wide angle adapters tend to be just a bit thinner to eliminate this problem.
I would use the wide angle adapter. It is thinner and covers less than the standard size.
Sorry I have no idea what you should buy.