Thanks everyone. Some random questions on doing away with graduated ND filters.
1. If you're using one photo, would it be better to expose for the skies and adjust the ground or expose for the ground and adjust the skies? (Note that I'm using medium format positive film - Velvia).
2. If I took two film shots and exposed for each area, which program would be best assuming again I'm using film. (Note this doesn't seem a cost effective way. If I really like a shot, I intend to drum scan it. I would have to do two scans in this case).
With transparencies, the only option is to base your exposure on the brightest areas of the scene, which would otherwise overexpose to glaring clear film base. With a single exposure the darker ground will simply have to be what it is, which under some circumstances may be quite dark. The opposite is true of color negative where it is best to bias the exposure somewhere towards the darker areas up to the point where the brighter sky areas start to block up on the negative. For film work, the best HDR technique is probably to shoot color negative. When last I used it, with some burning and dodging color negs had an effective dynamic range of perhaps 10 or more stops, versus roughly 7 stops for transparencies. But color neg is a much different look, and generally not as pretty as transparencies, depending on the subject matter. As I just mentioned, shooting transparencies is the game of "waiting for the light." You arrive at the scene, then hang out with fingers crossed until an attractive lighting situation within the range of the film either does or doesn't show up, repeat as needed.
The only combining program I can recommend experience is PS. If Elements or some other program has layers with individual adjustments, that's all you need.
HDR is kind of iffy with original files shot on film. HDR software somewhat depends on the original exif exposure data carried in digital files, although some programs allow you to guesstimate the relative exposures at the start of the process, and Photomatix will usually just plow ahead whether it has metadata or not. If you do drum scans the registration will probably be ok, but if you scan mounted slides the curvature of the film at the time of scanning will probably cause some registration issues which may or may not be a shot killer.
