Autoexposure Hugin Example Files

Ripon Cathedral Library. The contrast within the scene was quite large, varying from 0.63s exposure at ISO100 F8 looking down into the dark interior of the Cathedral, to 1/40th when pointed at the sunlit windows of the Library. But since these appeared on two different frames, I could simply expose separately. The traditional approach would have used a 1/5th base exposure together with a +/-3EV bracket to capture the darkest and brightest parts of the scene.

Traditionally, panoramas would be taken using a fixed manual exposure, bracketed if needed. But panoramic software has advanced to the point that they can handle the assembly and blending of source images taken with wildly different exposures. I am making available a set of files taken in Ripon Cathedral that shows the ease at which high contrast scenes can be tackled without having to take large amounts of bracketed photos.

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In this example, the base exposure throughout the scene varied by 6 stops (1/40th to 0.63s) hence there was a large amount of inter-frame contrast. But the contrast in any one frame (intra-frame) was just within the capabilities of my camera, hence I was able to take a 5+1+1 shooting pattern, without bracketing, and capture the scene without excessively blown highlights. This is variation of the usual 4+1+1 shooting pattern but with an extra shot that was taken aimed at the bright highlights of the sunlit windows.

Hugin Fast Preview Window. The position of the control points are marked by green crosses. The frames have been exposure matched and photometrically optimised for better blending. Normally, I use a 4 shots taken at -10 deg pitch and at 90 degree yaw intervals, together with zenith and nadir shots (4+1+1 shoot pattern). Here, there is an extra shot taken in between the 3rd and 4th shot at approximately 225 deg yaw that has captured the highlights of the sunlilt windows.

This extra shot was masked into the rest of the pano and invoked for an “underexposed” export of the stitch in addition to the normally exposed export. Hugin has no problems in handling the differently exposed frames and after photometric optimisation, the frames blend seamlessly. The normal and underexposed versions were combined using Enfuse and minor edits performed.

Top: Assembled panorama before photometric optimisation. Bottom: Optimised and exposure blended result (before final adjustments).

Hopefully this example demonstrates that panoramic software tools have come a long way since the traditional advice of locking off exposure was formulated. With some practice, the use of autoexposure when taking panoramas can be quite effective in speeding up workflow and creating a more efficient workflow. Of course, judgement is still required to use where necessary bracketing in order to tame intra-frame (as opposed to inter-frame) contrast.