You are probably right that it is a difference in rescaling (focus breathing). However it isn't clear to me why this should yield different sizes based only on the exposure changing. But it does.

A friend has pointed out that there is an option for Helicon Focus not to crop the result - that seems ...

I make focus stacked HDR pictures, using Helicon but I have a problem with Helicon's stacked output file sizes.

Here is the background. To make a focused stacked HDR image, I take a series of photos at different focal points - as one typically does for Helicon - at one exposure. Focal points are ...