David,Hi Woody, congrats on your IQ180. As I understand it, these are your steps for using the IQ180 for composition using live view:
1. Eyeball an initial composition, choose your lens focal length and orient the camera as a first guess.
2. Mount a variable ND filter to the front of the lens.
3. Capture live view with the IQ180 and adjust the setting of the ND filter until you can see a decent image.
4. Now, you adjust the camera orientation to get your desired composition.
5. Focus your scene using distance measurement with a Leica Disto.
6. Remove the ND filter.
7. Measure an initial exposure for the scene and take the shot.
8. "Work the composition", by re-mounting the variable ND filter and repeating steps 3 - 7 for each new composition.
I do not doubt the value of the live view feature of the IQ backs, but I find the repeated re-mounting of a ND filter to be a hassle. In the field, I almost never get the composition right on my first attempt, and am never sure of which composition actually "works" until I am analyzing my various captures on a computer. So, in general, I need to shoot many times from many different angles and positions, changing often from landscape to portrait orientation, etc. The thought of having to put a ND filter on and off between different compositions sounds painful to me.
I prefer the iphone solution myself, at least for composition, as it is much faster to test the different possibilities in the scene. The need to work quickly is often critical. For example, the available light in a landscape scene is somewhat "short lived" and fumbling with a ND filter may lose potential compositions.
David
There really is no need for a ND filter for composition..... just stop the lens down. Use the Disto for distance checking and set your HPF ring and you are done. If, however, you are using Live View for focus then you may, or may not need a ND filter. I have not needed one except for very bright scenes.
Victor