Section 7: Cleaning up the Equirectangular Pano
PTGui note: it is very rare that you'll ever have a pano with problems like the example below when using PTGui. PTMac, however, can often get results like this since it is harder to achieve the same really low control point distances in that app.
The stitching app has now generated a very nice equirectangular image of our panorama for us:
At first glance this rendered pano may appear flawless, but upon closer inspection two issues appear: 1) some seams aren't quite perfect, and 2) some parts of the pano are fuzzy. First, let's tackle the seam issue:
Here you can see that the stitch is off by about 1 pixel - the horizontal features are clearly disjointed. This is easily fixed simply by selecting one of the layers that overlaps this area, clearing its mask to black and then painting the mask with a white airbrush like so:
By setting the airbrush flow to a relatively low value (15 to 30%) you can smoothly blend out the broken stitch seam for a perfect result.
The second issue to deal with is the "fuzzy-zone" issue as shown here:
Here the seam is perfectly aligned, but one side is sharp and the other is very fuzzy. The fuzzy isn't because the camera was out of focus when this shot was taken. Rather, this is a result of PTMac using parts of the image from the edges of the fisheye lens where distortion is very high and the image isn't quite as crisp as it is closer to the center (this sample was shot with a Raynox conversion lens which is very fuzzy at the edges - a Sigma 8mm would never look like this). Luckily, we have lots of image overlap in our shots, so we can use Photoshop layer blending to selectively "repaint" parts of the image that are fuzzy exactly the same way that we fixed the alignment problem above. So, here we select the layer which seems to be the sharpest for this area of the pano, and we paint in its layer mask:
The home's gutter is now sharp and there's no visible seam at all. You should scan your entire pano for areas that are fuzzy and then fix them in this way. Doing this extra step is what makes the difference between a mediocre quality pano, and an amazingly crisp and clear pano, so you need to spend a lot of time going over every square centimeter of your panos looking for stitch alignment offsets and fuzzy zones.
Sometimes it's hard to see all of the errors in the equirectangular image, but it's much easier to see them when they're in an actual VR pano. To make life easier, I've written a free Photoshop plug-in called PanoPreviewer that lets you instantly preview the VR panorama right inside Photoshop. Here is a movie showing PanoPreviewer in action:
PanoPreviewer is only available for the Mac. No Windows/PC version is available or planned.