atropine 0 Posted April 2, 2007 (edited) HI, Haven't got any cameras yet, but looking into getting a couple for home external. I don't understand the requirement for auto aperture lenses when security cameras can alter exposure via shutter speed alone via shutter durations of 1/50th to 100,000. I was looking at lenses and ofcouse the auto aperture lenses are way more expensive, but is there any reason at all to use them? I'm thinking they are an archaic function from the days when security cameras used to be picture tubes and there only was a single shutter speed, and for some reason instead of dying out with picture tubes they've remained. I understand the use of automatic aperture when wishing to keep shutter speeds stable. (shutter priority) and would be necessary for television production use, but in situations where you don't care what the shutter speed is, do auto aperture lens hold any advantage? Edited April 2, 2007 by Guest Share this post Link to post Share on other sites
phred 0 Posted April 2, 2007 atropine What an appropriate name for a question on irises. Auto iris is usually essential for outdoors of where light levels vary considerably. Current CCDs have a limited dynamic range, an iris effectively increases the range. The old Vidicon tube cameras actually had an extremely wide dynamic range so a manual iris was fine. Share this post Link to post Share on other sites
kensplace 0 Posted April 2, 2007 you can get second hand lenses real cheap on ebay for home use Share this post Link to post Share on other sites
atropine 0 Posted April 2, 2007 atropine Current CCDs have a limited dynamic range, an iris effectively increases the range. Ok, so although a camera may be capable of correctly exposing a F1.4 lens wide open in full sunlight via a very fast shutter speed the quality suffers due to this poor dynamic range. I would guess dynamic range is seen as the contrast - the amount of shades of grey between black and white. Thanks Kensplace. there sure does seem be some really cheap 2nd hand lenses on ebay, about 1/10th the price of new. Worth having a gamble on. Share this post Link to post Share on other sites
kensplace 0 Posted April 2, 2007 If its for home use it is worth the gamble. Usually they are fine, only had a few bad ones, but at the price I paid, I could buy lots of lenses before I even came close to the price of one new one. When it comes to zoom lenses, it gets even better - some 500 dollar + lenses for about 20 dollars, bought one lens that probably cost thousands (25 to 350 mm) for 20 pounds, about 40 dollars - works perfect... Would stay clear of ebay for business use though, no warranty.... Share this post Link to post Share on other sites
forecamsales 0 Posted April 2, 2007 i'm wondering the shutter speed of auto aperture depends on how the DC driver works,for the advantage,comparing to manual iris,it could be more convenient and just two status,close or open,but once you installed the camera with manual iris at a hard-touched position,it seems simlilar to auto iris given the stable light. Share this post Link to post Share on other sites
videobruce 0 Posted April 2, 2007 Where you really have a real problem is with snow! Also, white garage doors, houses & buildings. The shutter can't increase enough to stop down the reflection. The price difference between manual and auto iris 2-3x lenes I have found is $10 - $30. Unless you are looking for a telephoto or a larger zoom ratio $50- $60 (US) should get you something halfway decent. Another advantage (unless you want/need this) is you don't have the 'strobe' effect (frozen rain drops for example). Share this post Link to post Share on other sites
