May be I was so bored that went out yesterday and bought the PC-E NIKKOR 24mm f/3.5D ED lens. On the other hand, I can also say that I have considered this lens for a long time and for the coming trip to the US finally pushed me to act. The lens is a manual lens that has two functions: tilt and shift.
In order for all the vertical lines in the above image to be parallel, I have to not only keeping the camera level but also have to position the camera right in the middle between the ceiling and floor. Here, all I have to do is to keep the camera level and "shift" the lens up or down a bit to get the composition that I want.
Then I can turn the lens 90 degree. This time, I have to position the camera level and in the middle between the ceiling and floor then shift the lens from left to right. I took one picture on the left and one on the right. Stitching the two together, I have a perfect panoramic image. Usually it is hard to stitch images from 24mm lens for panoramics, here it was piece of cake. Otherwise, I would have to use a 85mm lens, position the lens at its perfect nodal point then rotate the camera to take several images to get a perfect panoramic.
Now I tried the "tilt" function. I placed the camera in the "portrait" position, first focused on the flower then started to tilt the lens downward till I could see the sofa and piano came into focus. I rechecked the focus then took the picture. Everything now is all in perfect focus. I have to correct the prospective a bit in the PTLens because the "tilt" function not only shift the focusing plan but also the prospective. It could be a problem in the film days but not at digital age. It will also not be a problem for landscape photography. The idea is to tilt the lens to get perfect focus for very close foreground and distant background then shift the lens for panoramic.
Here is a more dramatic demonstration of the "tilt" function. I managed to get both the watch and all the way to the pencil holder all in perfect focus.