Hugin ­ Stitching auto-exposed panoramas

This tutorial is a preview of features in the upcoming 2009.2.0 Hugin release.

The standard advice for shooting panoramas is to disable all 'automatic' camera features, i.e. to use fixed focus, aperture, white balance and shutter speed. This advice hasn't changed, but many point and shoot cameras don't allow you to alter any of these settings, this tutorial shows you how to get the best from a sequence of photos taken with auto-exposure.

Hugin has long used seam blending with enblend for creating invisible seams between photos with similar exposures. Hugin also uses exposure fusion with enfuse for selecting the best parts from photos with dramatically different exposures - Usually this exposure fusion is used for assembling stacks of bracketed exposures, but it is also good for blending partially overlapping photos.

Here are four shots taken with a cheap cameraphone:

The range of variation betwen the sky and ground photos is around 3EV, this is much more than can be hidden by seam blending with enblend. Here is the (not so good) result from stitching this in Hugin using the default Normal -> Blended panorama output option which corrects exposure before seam blending:

Note that to equalise the exposures of the overlapping photos, Hugin has overexposed the sky and underexposed the ground. Note also that the overlapping photos have little common detail, resulting in an ugly seam between top and bottom.

Hugin now features an additional Exposure fusion - > Blended and fused panorama output option. This uses a two step process, first images with a similar exposure (within a 0.5EV range) are seam blended together with no exposure correction, then these blended layers are exposure fused into the final panorama result:

That's it, this isn't the highest quality example but hopefully it shows the possibilities of this new Hugin functionality.

September 2009 ­ Bruno Postle