Suppose one wants to use a director's viewfinder, such as http://cinemasupplies.stores.yahoo.net/marvdirview.html , with the Letus 35XL.

Tentative method: select to use 35mm format; but use a focal length adjusted to take into account the 1.9x magnification of the Letus. For example, using a 50mm prime on the Letus, one would use a value of 95mm focal length on the director's viewfinder.

Would this work?

The Letus35 flip for XL is likely to be closer to, perhaps a little smaller than the director's viewfinder normal field of view.

In this Letus version, the aquired image off the groundglass is closer to the 24mm x 18mm movie frame, than to the 36mm x 24mm still camera image frame some other adaptors use.

My personal preference would be to put aside the mathematics, test for the actual field-of-view and cut up a small piece of filter gel to make a custom safe-area mask to fit inside the director's viewfinder if this is a possibility, so you immediately see and know what you will get.

Alternatively, one of the inbuilt selectable field of view masks may well be identified as a fit close enough to the Letus35 field-of-view even if it is not the correct choice for 35mm film field-of-view.

The director's viewfinder may well lead you into error otherwise.

Transposing field-of-view and depth-of-field numbers on the fly is only going to get in your way creatively and timewise if you are under pressure.

If you don't already own a Letus35 then ignore my comments. I am also not an industry professional so apply similar judgment to my comments.

Transposing field-of-view and depth-of-field numbers on the fly is only going to get in your way creatively and timewise if you are under pressure.

My thinking is that if I can find a viable procedure & become polished in using it, it could be quite efficient. As far as the viewfinder goes, it would seem more suited to location scouting & previsualisation.

One of these days I'll try to get hold of a viewfinder & test it out following the gist of your recommendations.

Thanks,
H.