In Part I, we are going to talk about using proper hood for the lens. Hoods are one of the best and cheapest way to extract the best optical potential from a lens. You may be very surprised what a difference a hood can make to your pictures.
I have had the Voigtlander Skopar 8.3cm f4.5 lens for a number of years. It was first used on the Canon 5D but the results were not good at all. There was always a white area in the center of the picture, even when shot indoors. I first thought it was the internal reflection from the lens barrel, though it might be a factor, but even after spaying the barrel with black paint, it didn't make too much of a different. I then added a hood to it, and it improved things markedly, but the foggy center remains in most pictures, until one day I put on a very long hood. Problem mostly resolved, although in some situations, the white spot is still visible, but not very frequently.
The picture below shows the effects of using no hood, short hood, and a long hood:
Left: No Hood, Middle: Short Hood, Right: Long Hood. Dramatic, eh? Click for larger.
As you can see, the right hood made a huge difference. But where to find the proper hood? Most old lenses we get do not come with hood, or they were never designed to accept one. Fortunately, they are easy to make using black craft paper and glue/tape. Sure they don't look very nice, or even ugly, but that never deters me :) I have thick skin! I am luckier than most since I have so many spare parts from disassembling old lenses and other devices, and because I am a packed rat. I keep a lot of junks around. In the example of the hood(s) for the Voigtlander Skopar, I found some black tubes that fit almost perfectly. The tubes were just taped to the front of the lens with electrical tape.
How do you determine the length of the hood? At first I thought the one I put on the Voigtlander was long enough, and any longer would vignette, but I was wrong. You would be surprised to find that hood can be very long before they would vignette. The best way to find out is to make one with paper and experiment until it provides full protection from stray light, but would not vignette. I can be wrong here, but I think the length of the hood could be as long as the focal length of the lens.
So, put your hood on your lens, and make beautiful pictures with quality the designers intended!