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Dear Charlie,
I am fairly new to the CCTV industry and was hoping that you could answer a question that is driving me mad. What does the camera format do and which format size should I use inside or outside?
David Hollis
California
Dear David,
To understand format, we must first define it. A camera's format size is determined by the usable portion of the imager as measured diagonally across the chip or tube. As an example; if we take the rectangular, usable portion of a charged coupled device (CCD), otherwise referred to as the chip, and we measured from the upper left corner to the lower right corner, we would know the format size of the camera. If it were 2/3" across, the camera is a 2/3" camera; 1/3" across it would be a 1/3" camera; et cetera.
To understand the effect that the format size has on the out come of the video image, we need to do a short history lesson. Ten years ago the primary cameras used were of the tube type. We had, at that time, two primary tube types that were used throughout the CCTV industry; the one (1) inch and the two thirds (2/3) inch. The one inch tubes has a slightly better resolution and sensitivity when compared to the two thirds inch tube cameras. They were also considerably larger and more expensive. Because of their better sensitivity, the one inch tube cameras were used primarily outside in lower light situations. Because of their resolution, the one inch cameras were perfect for long telephoto and zoom lenses. Since the majority of indoor applications had plenty of light and were generally close range, the two third inch camera was best suited. Obviously cost and size also factored into where these cameras were used.
When we entered into the solid state world of the chip camera, we started by using the same theories for camera usage. That is to say, the 2/3 inch was recommended for inside while the one inch was developed for outside use. However what has happened in the past few years has more or less determined that the format size of the camera is becoming less and less important. Our enhanced technology is now producing one fourth inch cameras that have the same abilities (if not more) as the old two thirds inch tube cameras. It is true that you can still achieve a slight improvement in sensitivity and/or resolution with the larger chips, but this is fast becoming inconsequential. Just one short year ago, I would have recommended that you avoid one third inch cameras in most of your outdoor applications. Today however my only conclusion is if in doubt, hold two cameras up in the position that you are trying to cover and see which provides the best image for your needs.
As a wrap up, you will find that the format size of the
camera is becoming less important with each year and that the advancements in
the overall technology will soon dictate that format become a obsolete
terminology.