With a regular 35 mm camera it gets a little more tricky. As mentioned before you can do it through software (I use Picture Window Pro, which has a very neat feature for perspective correction, but PSP or PS should be able to do the same. Its not the same as pincushion or barrel distortion correction, though). You can also do it, when shooting. Imagine taking a picture of an amp. You want all the lines framing the faceplate to be be parallel, yet the sidepanels and the top should be visible. Imagine, pointing your camera straight at the faceplate, the camera/filmplane is parallel to the faceplate and so there is no distortion. Now move the camera to the left and up without tilting or rotating it (you have to step back far enough, so the faceplate doesn't fill the entire frame)!!! The side and top panels become visible, but since your camera is still parallel to the faceplate, there is no perspective distortion of the lines framing the faceplate. Your amp will be in the lower right corner of the picture, though and you have to crop away most of the picture that doesn't show the amp. Hope, that wasn't too confusing...