Yes your information is correct. A black ring around your image usually denotes that you used the wrong formatted lens on the camera. When picking lenses for cameras, there are six different factors that must be taken into consideration to insure compatibility of the lens and camera. They are:
1. Does the situation require a fixed or auto-iris lens? 2. Is the camera equipped with auto-electronic shuttering and if so, do you plan to use it? 3. Is the camera a C or CS standard or is it designed to work with either format? 4. Is the camera equipped to work with a "Video" or "DC" lens or both? 5. Is the camera color? If so a color corrected lens must be used. 6. What is the format size of the camera?
For the purpose of answering your question, we must look at number six. Just as all cameras come in different format sizes (referring to the size of the imager), so do lenses. The lens must meet or exceed the size of the camera. Therefore if you are using a 1/3 inch camera, you must use a 1/3 inch or larger lens. If you are using a 2/3 inch camera, you cannot use a one half inch formatted lens or you will have the symptom that you described in you note to me.
To help you better understand, you can do the following experiment. You will need two pieces of equipment. A screw ring from a canning jar and a cardboard tube from the inside of a roll of paper towels. Cut the cardboard tube so that it is two inches (2") long. Hold the canning ring up to your eye first. What do you see? With the canning ring, you should see the whole area that you are looking at with no obstruction. That is because you have a one inch formatted lens on a one half inch camera. Now look through the two inch paper towel tube, you should have a sort of tunnel vision. This is because you have a one third inch formatted lens on a two third inch camera.
Please note that the image you were seeing did not change in size when looking through the canning ring or the 2" tube. This is because format has nothing to do with image size. That is determined by the focal length of the lens which is a whole different subject.
Hope this helps you out with your understanding of lens to camera relationships.
