One of the “fundamental” rules for capturing panoramas is that all of the individual frames must be shot using the same exposure settings or else the exposure differences will be visible in the merged images. But when merging RAW images in Lightroom using the Panorama Photo Merge tool, it is no longer necessary to use the same exposure settings for each of the individual base images.
I collected some images for an impromptu test of this capability on my last drone excursion. I had flown the drone, a DJI Mavic Pro, about a mile away from my location with a strong tailwind, so I knew I needed to start flying back with plenty of battery in reserve. Flying over the canyon, I found this composition looking down into the canyon, but the image did not include enough of the sky. The shutter was set at 1/100 sec* to capture the darker details since the canyon was in shade. I decided to swing the camera up and capture a second image for the sky and realized that the exposure was far too bright. I lowered the shutter speed to 1/500 sec and got the second image. Because I was so pressed for time when flying over the canyon, I decided not to get another exposure looking back down at the faster shutter speed.
Back at home, I merged the two exposures using the perspective projection with no warp or fill. I think because Lightroom produces a DNG file for the merged images, it is able to adjust the exposure of each frame as it processes the panorama. The end result is a seamless stitch of the two base images that includes all of the shadow and highlight detail present in each one.
Having the ability to create panoramas using “bracketed” exposures without having to actually collect 2 or more true brackets for each frame is really useful for a lot of shooting situations, particularly for drone photography when trying to manage many other variables that make capturing panoramas more challenging.
*When using the DJI Mavic Pro, I always capture stills using the built-in HDR capture setting with raw DNG output. It takes a bit longer to capture an image, but the resulting file will have better shadow and highlight detail and greatly reduced noise compared to a standard raw image. For high dynamic range scenes, I will typically capture two or more exposures manually bracketed. I do not recommend using the built-in auto bracketing feature.