### Error in transormation using FindHomography

I have two images (img_1 and img_2) of a plane "A" acquired by the same camera in two consecutive times. Between these two instants the camera performs a little rotation around one of the two axes x, y (considering that the z one points to the plane "A" ...so the transformation between the images is perspective.

My goal is to find a point (previously detected in img_1) in img_2.
So i use FindHomography function and than i multiply the coordinates of such a point (setting z=1, normalized as suggested here: findhomography) with the matrix obtained.

The problem i that the new point in img_2 is always shifted a bit in one direction with respect where it should be....

what am i doing wrong? could be something about the scale factor? (take into account that the transformation matrix for translational movement of the camera is ~~computed) properly ~~computed properly).

My code is the same of this example obviously my code stops at:

```
Mat H = findHomography( obj, scene, CV_RANSAC );
```

..than, in the main function, i simply do:

```
dstMat = H*srcMat;
```

where scrMat is the point in img_1 (setting z=1) and dstMat is the point in img_2