Vignette Removal When Creating Panorama
I recently relocated from the pitch black skies of Arizona to South Carolina and its somewhat lighter skies. I don't know if it's the type of light pollution (backlit skies) or just the fact that the skies are lighter in general, but I'm finding that my panoramas aren't stitching quite as nicely as before. The biggest issue I'm seeing is heavier vignetting, with the vignettes actually getting stitched into the final panorama. Since I went through a trial and error process to narrow down a good combination of steps, I figured I'd share what I discovered.
- Camera/Lens: Canon 5DMkIII + Samyang 14mm prime
- 8 images, vertical orientation
- f/2.8, 30 seconds, ISO 3200
- Basic processing on RAW images done in Lightroom
- Applied Lens Correction in Lightroom, using the Samyang profile found online
Initially, I decided to try stitching the images in Photoshop. To do this, I highlighted all 8 in Lightroom, right clicked on one of the images, and selected "Edit In" > "Merge to Panorama in Photoshop..." When Photoshop launches, I chose the default settings (Auto Layout, Blend Images Together) and clicked OK. This is the resulting panorama that Photoshop creates.
No Correction for Vignetting
After a quick glance, it's clear that this would be unacceptable as a print. The dark vertical lines that define each of the images (since each image has a vignette to it) does not look good as a panorama. So I started to think of my options. My first thought was to let Photoshop take a guess at the vignette removal since that is one of the check box options when Photoshop launches to create the panorama. So I did it again, only this time I checked that box.
Photoshop Vignette Removal
Well, it looks like Photoshop did a good job at taking out the vignettes, but it looks like it did some serious level work and moved the white and black points. This is clearly not a good rendition of the panorama, especially if you look at it side by side with the individual images that are at the top of this article.
So if Photoshop does a horrible job at stitching the panorama without vignetting issues, what's the next option? What if we feed Photoshop images that have some of those vignettes removed beforehand. My first attempt was to go back to the Manual tab of the Lens Correction panel in Lightroom. I pushed the Lens Vignetting amount from +50 to +75.
Lightroom +75 Lens Vignette Correction
There was very little difference between the +50 and +75 lens vignette correction. Let's push it to +100 and see if there's anything there.
Lightroom +100 Lens Vignette Correction
Clearly there is an issue here, although it looks like Photoshop chose to ignore one of the images during the stitching process. I had one more idea. I knew that Lightroom was doing a pretty good job with providing me with some good vignette-free images, but for some reason Photoshop was having issues with it anyway. So my next idea was to try these two settings again, only exporting the images as full resolution JPEG images and importing them into PTGui and doing a standard panorama stitch.
Note: I did not try Microsoft ICE or any other panorama stitching program, but if I had to guess the results would be similar provided you're starting with the same baseline set of images that had the vignetting removed or partially removed within Lightroom.
Lightroom +75 Vignette Correction, Stitch with PTGui
Now that's what I'm talking about. Just for kicks, let's see how it looks with +100 lens vignette correction in Lightroom. The reason I'm doubtful it will get any better is because to my eye, Lightroom tends to add a fair amount of red noise to the vignetted areas when it tries to remove it. This seems logical since you would think that part of the image would be pretty dark and you're basically rescuing detail in an area that doesn't have much. Let's just see to be sure.
Lightroom +100 Lens Vignette Correction, Stitch with PTGui
My assumptions appeared to be true. You can see a lot of reddish noise along the bottom edge of the image in the dark sand. I'm sure some of this could be rescued by manually vignetting the entire panorama after the fact.
However, I have to say that the previous image is more of what I'm interested in. I don't have to do any of the leg work of vignetting it because a very slight one (at least as much as I would put in myself) is already there.
Anyways, here's the final image after some minor editing. I hope this helps someone out there.