Here’s a few tips how to ensure you will get better result when taking a picture for photomerge. Because your source photographs play a large role in panoramic compositions.
a. Overlap images sufficiently Images should overlap by approximately 25% to 40%. If the overlap is less, Photomerge may not be able to automatically assemble the panorama. However, keep in mind that the images shouldn’t overlap too much. If images overlap by 70% or more, it can be difficult to work with them, and blending may not be as effective. Try to keep the individual photos at least somewhat distinct from each other.
b. Use a consistent focal length Avoid using the zoom feature of your camera while taking your pictures.
c. Keep the camera level Although Photomerge can process slight rotations between pictures, a tilt of more than a few degrees can result in errors when the panorama is assembled. Using a tripod with a rotating head helps maintain camera alignment and viewpoint. When photographing a panoramic scene from a high place, the natural inclination is to keep the horizon level in the viewfinder. However, this actually produces a noticeable rotation between images. Try using a tripod to keep the camera level when taking photographs in this situation.
d. Stay in the same position Try not to change your position as you take a series of photographs, so that the pictures are from the same viewpoint. Using the optical viewfinder with the camera held close to the eye helps keep the viewpoint consistent. Or try using a tripod to keep the camera in the same place.
e. Avoid using distortion lenses Fish-eye and other distortion lenses can interfere with Photomerge.
f. Maintain the same exposure Avoid using the flash in some pictures and not in others. The advanced blending feature in Photomerge helps smooth out different exposures, but extreme differences make alignment difficult. Some digital cameras change exposure settings automatically as you take pictures, so you may need to check your camera settings to be sure that all the images have the same exposure.
2. In the Photomerge dialog box, click Browse to open all the file you want to merge. Select Attempt To Automatically Arrange Source Images if you want Photoshop to try to line the images up in their proper order. Deselect this option if you want to arrange the images in the lightbox yourself.
3. Click OK when you have open all the file.
4. Adjust image position by dragging or rotating it if necessary. If you want to save each image in the composition in individual layers, select Keep as Layers. (This is useful if you need to correct the color of each image separately.)
5. Click OK to get the photomerge result.
Note: You can use crop tool to cut the unwanted edge of the picture.