| When you finally set out to select your | | | | related properties (i.e. the depth of focus). |
| Surveillance Camera, for realizing your well | | | | The overall result is a matter of compromise |
| thought out Home Security project, you should be | | | | whereby, by sacrificing somewhat one feature |
| advised that, besides other elements equally | | | | one gains a better response from another one. |
| important, the lens plays a determining part in the | | | | Fixed focal length is a common selection: although |
| camera performance. | | | | limiting somewhat the dimension of the space |
| It is the lens that determines the amount of light | | | | where all objects result clearly perceived (depth |
| entering the camera. Besides the quality of | | | | of focus), it simplifies the mechanical construction |
| materials and of manufacturing, usually reflected in | | | | and reduces the price. |
| the price, some of the lens characteristics have | | | | You may be familiar with autofocus feature found |
| much bearing on the viewed picture. | | | | in modern digital cameras. There is no comparable |
| Even if you do not want to become an expert in | | | | capability in cameras because they must work |
| lenses, there are a few concepts that you should | | | | unattended. A lens whose focal length can be |
| understand before you purchase your surveillance | | | | manually adjusted is called a Varifocal lens but |
| camera. | | | | should not normally be considered for surveillance |
| The subjects are well known from the field of still | | | | purposes. |
| photography, so that the principles should not be | | | | Equally too sophisticated for the application would |
| completely unfamiliar for whoever has some | | | | be a motorized zoom lens, capable of being |
| practice of family picture taking even at a very | | | | commanded from a distance to select the |
| basic level. | | | | preferred level of detail between wide-angle and |
| In most surveillance cameras, lenses are | | | | telephoto. |
| interchangeable. Therefore you should decide if | | | | Fixed iris or aperture is another characteristic to |
| the picture seen on the monitor is satisfactory | | | | be considered that simplifies construction and |
| for your application, with reference to the depth | | | | operation, albeit with some compromise on picture |
| of focus, the angle of view and the amount of | | | | quality. It would probably be easier to provide |
| detail you want to distinguish. | | | | sufficient illumination then going for more complex |
| In case you are not satisfied with the | | | | optics. |
| performance of the standard lens supplied, you | | | | In conclusion, despite the nice and costly |
| should ask to see how a different lens would | | | | alternatives available, for a simple home |
| improve the images you want to observe. | | | | surveillance system it would be advisable to select |
| Normally one should select the best overall picture | | | | one of the simplest lenses, provided that the |
| for the purpose. Note that by changing one of the | | | | quality of the picture is sufficient for the intended |
| characteristics (i.e. aperture) one modifies other | | | | purpose. |