Catedral de Cristo Salvador, the Cathedral of the Savior, the oldest Gothic cathedral in Spain. Construction began in 1091 and was completed (mostly) by 1475. It is both cathedral and fortress with the apse forming one of the towers in the wall of the city. Our visit to the cathedral was one of the highlights of our recent trip to Spain and France, my first time overseas.
I've wanted to visit the great cathedrals of Europe for almost my entire life, and ever since I became a photographer, getting an interior panorama of one of these ancient structures has been on my list. I spent more than 2 hours wandering around the interior of the cathedral with my camera, in awe of the unbelievable and almost incomprehensible skill of the builders and artisans, and hoping that I could somehow capture the raw image data that would allow me to produce a photograph that could somehow convey a hint of what I saw.
This image shows the view from the crossing looking forward into the Capilla Mayor with both transepts captured to the left and right. This image is a composite of 86 individual photos captured with a 12 mm wide-angle lens on my Sony a6500 APS-C camera to capture a more than 180-degree field of view (the upper windows to the left and right are actually behind where I was standing). I originally captured 215 (43x5) raw images shot in 5-image brackets at 2-stop intervals. I was shooting handheld (no tripod); all images were captured at ISO 400 using a base exposure of 1/40th of a second. Even though I was using the in-body image stabilization, the longest exposure (0.4 sec) of each bracket was blurry, so I had to remove 43 exposures. I also removed the shortest exposure (1/640 sec) because it was not needed-even the brightest highlights in the upper windows were not blown. With 129 exposures remaining, I learned that Lightroom has a limit of 100 exposures for the HDR Pano Merge tool. After reviewing the exposures, I decided to keep only the darkest and brightest remaining exposures (1/10th sec and 1/160 sec, 4 stops difference) for a total of 86 source images.
All of the processing was done in Lightroom using the HDR Pano Merge tool. Unfortunately, I didn't make a note for the panorama settings. After merging, I used the Transform tools to adjust the perspective, then cropped the image to the final version. The resulting image is almost 92 megapixels. I initially thought I would need to use Photoshop to make the perspective corrections, but I'm happy with the Lightroom result. I had to make some strong adjustments using the Vertical, Aspect, and Scale sliders to correct the distortion and retain much of the field of view-by default, Lightroom removed a lot of the outer parts of the image to the left and right.
In capturing the images of this cathedral, I also found a very practical use for ISO invariance. The base exposure for my brackets (1/40th sec, f/5.6 at ISO 400) is underexposed by about 3 stops for the center image of the chancel. Since I was using a 2-stop bracket interval, I picked 1/40 sec as the base exposure to allow me to get a sharp image at 2 stops longer exposure time (1/10th sec). Any longer would risk getting a blurry image (as evidenced by the brighter exposures at 0.4 sec which I had to discard). So I should have been capturing these images using a 2-stop higher ISO (ISO 3200) which certainly would have resulted in the loss of highlight detail (needlessly since a faster shutter is used). However, based on my previous testing of ISO invariance of the a6500, I knew that I could simply set the exposure to a "safe" base exposure and make whatever exposure adjustments needed in Lightroom. And since HDR processing inherently reduces noise, the final image is free of noise, even in the deep shadows.
Be sure to check out my other post (coming soon) of a virtual tour of the interior of the cathedral.
Update (April 2020): This image was critiqued by Blake Rudis at f.64 Academy (he said that anyone who goes through the effort to capture and process 86 source photos deserves to have their final image critiqued!). Blake's criticisms were very constructive. His main comments were that the image was too dark, it had an overall cyan color cast, and the highlights in the upper windows had been pulled down too far. I made some quick edits in Lightroom to address these comments, and I think the image is much better for it. Thanks Blake!