Stitching scanned images

[a d]

Hello
I am using Hugin (v 2012.0.0.a6e4184ad538) to stitch two scanned pictures together. For this particular job it is essential that images are not scaled (only rotated and translated), that the exposure is not corrected and that I keep the same resolution as the original pictures (always 100dpi). The images have been manually cropped, so they do not always have the same size. I am a little bit lost in all the potential settings, and I was wondering if somebody could help me. I have read the relevant tutorial (http://hugin.sourceforge.net/tutorials/scans/en.shtml), but in this tutorial the image orientation Z parameter is optimised, which if I understand well would potentially result in one of the image being scaled down or up relative to the other. When I optimise the image roll, X and Y parameters only, I get strange results: it seems that one of the images is scaled, and I don't understand why. I get seemingly better results when I optimise image roll and lens x and z shifts, but I would like to be certain there is no scaling in that case. Should I optimise the view parameter too? With regard to the exposure, I simply un-ticked all parameters in the exposure tab, and used the "exposure corrected, low dynamic range" in the stitcher tab. Is that the correct thing to do? Finally, how do I keep the same resolution as the original pictures?
Many thanks for your help.
Arnaud

[Merlin Kramer]

Hey, I did a similar Thing with paintings (on cardboard or canvas) from school and here is what I did:

1. Load Images. Type 10 in HFOV
2. in the Images tab, select all of them and do Feature Matching, Settings: Hugins's CPFind, Points per Overlap: Doesnt Matter with CPFind, it uses a different Algorithm to spread the Control Points
3. turn the images with roll in 90° steps so the are the right way up
   
4. in the Control Points tab, select the same image on both sides (it needs to have a visible border), then set a cp on one end of the border and the corresponding point in the other view on the other end of the boarder, click fine tune (or press f)
   
5. in the Optimizer Tab, optimize "the Custum parameters below": deselect everything, then select roll for everything, X, Y and view(v) for everything but the first Image.
6. in the Image Tab, select all Images, then Cean control points
7. optimize again  with the same settings
8. select Projection Rectilinear, calc FOV, calc optimal size, fit to crop images
9. click stitch