Focus Stacking for increased depth-of-field.

To use this technique, one must take several shots of the same object, each focused at a slightly different point, so that the desired depth of field is covered. The images are then combined (stacked)  in post-processing, to produce one image, sharp over the entire field (the number of required images and depth difference between points, depends on the 'real' depth of field at the distance and aperture used).

In macro work it can be done in two ways:

1. Camera and object are in fixed positions. The lens focus ring is adjusted to focus at different points for each image, to cover the desired depth.

2. The relative position camera - object is changed, without changing the lens focus setting. For instance, for the first image focus the lens on the closest point of the object which should be in focus. Then move the camera towards the object at the desired steps and take an image at each step, without touching the lens focus (of course it helps to have the camera on a 'focusing rail').

Which way is the preferred one, and why?

I don't know how other softwares which may be used for P.P. behave, but the 'Align Layers' function in Photoshop, not only aligns the layers position relative to each other, but also the image sizes.

Thanks, Moshe