jizzer Posted October 19, 2005 Share Posted October 19, 2005 Hello, I have bought 2 cheap Baxall CD9312/LV cams Mainly to experiment with and learn the various functions and settings of a cctv camera. I have downloaded the Baxall guide to cameras which is very informative. The question I have is regarding back focusing The guide says the following " Automatic Iris and direct drive len's......Fully open the iris by covering with a suitable netral density (ND) filter.Set the focus to infinity.View an object greater than 2 metres away.Focus the image using the back focus screw.Remove the ND filter and set the lens focus as required" I understand this but as the lens is a varifocal 4-8mm when I set the lens focus to infinity where should the other control ( Tele/Wide)be The one with W-T on.should it be in the middle of its travel or to one end or the other when back focussing Also One camera has a DD drive lens the one with the little plug and the other has An AI lens the one where the wires connect to the terminals at the back of the camera. whats the advantages over either type of lens apart from the DD lens appear to be cheaper. Another quick question the first dip swith is labelled ID what does this one do I cannot see a reference to it in the info I have I assumed it meant Camera ID and that when switched to on it might put a number or letter on screen to identify the camera but it does not While the guide is very good does anyone have any other tips or tricks when setting up a cam to get the best results . Thanks Link to comment Share on other sites More sharing options...
Doktor Jon Posted October 19, 2005 Share Posted October 19, 2005 Hi jizzer, I haven't used your camera but the principles for backfocusing are the same for any camera / lens combination. If you are using a varifocal or zoom lens, always set it to the longest focal length (i.e. the telephoto setting); the reason is that the "depth of field" (at maximum aperture) is minimal, so after you've set the back focus, as you then change the lens setting towards wide angle, the DoF will increase, and if the lens focus shifts slightly (usually because it is of a poor optical design) hopefully, it will still be within the expanded DoF, and so will still appear sharp throughout the 'zoom' range. The two lens types you mention, DD and AI differ in that the former does not have an amplifier board built in, relying instead on that function being built into the camera itself. Some years ago, no cameras had lens iris amps built in, so anyone wanting to use auto iris, had to buy the "AI" type with the amp built in (or the now defunct "EE" type with built in light sensor). You will often find that the Neutral Density or "ND" filtering built into the lenses will also differ, with DD lenses often filtered to f64, whilst AI lenses can be filtered to f 360 and beyond. It is really not possible to generalise too much, but AI lenses, particularly larger format ones, are often optically superior to some of the more basic DD lens designs. That is a general observation, and there are sometimes exceptions. The "ID" function may well be an on screen number generator (I'm sure someone will know the answer), but you may well have to set a (or a couple of) small rotary switches to select the ident. The only other thought is it may be a function common to the camera PCB used for a range of cameras, but not necessarily enabled on this particular model. Link to comment Share on other sites More sharing options...
Mavrick_001 Posted October 19, 2005 Share Posted October 19, 2005 If it's a coax jobby take no notice of the id function, however if it's network cam (which I'm sure it won't be) then it may be of use addressing it.... tbh I wouldn't bother with it.... baxall... say no more!! As above post qfa... there's all you need to know If it's a coax jobby take no notice of the id function, however if it's network cam (which I'm sure it won't be) then it may be of use addressing it.... tbh I wouldn't bother with it.... baxall... say no more!! As above post qfa... there's all you need to know CCTV Intruder Access Control Tony Hughes, Proprietor, TRADE MEMBER Link to comment Share on other sites More sharing options...
jizzer Posted October 20, 2005 Author Share Posted October 20, 2005 If it's a coax jobby take no notice of the id function, however if it's network cam (which I'm sure it won't be) then it may be of use addressing it.... tbh I wouldn't bother with it.... baxall... say no more!! As above post qfa... there's all you need to knowIf it's a coax jobby take no notice of the id function, however if it's network cam (which I'm sure it won't be) then it may be of use addressing it.... tbh I wouldn't bother with it.... baxall... say no more!! As above post qfa... there's all you need to know Thanks for the comprehensive reply Mavrick that helps alot Link to comment Share on other sites More sharing options...
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