BLENDING SEAMS IN STITCHED PANORAMAS - PHOTOSHOP TUTORIAL
This is an output image from Panorama Tools. It is a layered PSD file with masks, there being four layers. Image 3 is very slightly darker than the others, spoiling an otherwise nice stitch. (The darker image in the middle will be more obvious if you drag the window to and fro or scroll the image). The way to improve the blend of images at a seam is to feather the left edge of the upper image just in the area of the sky, and leave the existing harder edge join in the lower part of the image (to avoid blurring where there is a lot of detail). This is quite easy to do.
Switch into mask editing mode
Display the layers palette:
(Note: This shows the palette in Photoshop CS and earlier versions. In CS2, the second column has gone. The editing mode - image or mask - is then indicated by a highlight border to the thumbnail image).
Click on the black and white mask thumbnail in layer L03. This puts us into mask editing mode and the paintbrush symbol in column two will change to a circle. In this mode, you can paint on the mask with black, which will have the effect of making the corresponding image pixels transparent. Paint with white and the pixels become opaque. Shades of grey give degrees of transparency. As you paint on the image, you will see the affected parts of layer L03 coming and going according to the colour of the paint brush. The mask itself will not be visible, but you can show it as a red overlay by pressing the backslash key. (Press it again to switch the overlay off).
Here, then, you see the outline of the mask in L03. Now make a selection with the rectangular marquee around the seam in the sky, and then bite a lump out of the bottom right corner using the lasso tool with the ALT key. This confines the selection to the sky, more-or-less.
With the foreground colour set to black, and background colour set to white, select the gradient tool and pull it across left to right within the selected area. Hold down the shift key while you drag, to keep it aligned with the horizontal. The start and end points of the drag should be well within the selection to keep the gradient within the area of overlap of the two images. (You'll soon see what happens when you go too far - just repeat the gradient).
Now you can deselect (ctrl/d) and turn off the red mask (backslash key) and see the effect.
This is much better. You can return to normal image editing mode by clicking on the image thumbnail in L03, or go on to edit another mask. (I did the seam on the right as well in the above image).
17th August, 2005