> > My question is not about face recognition. Its another big problem. My > question is about zooming till possibility to recognize face (recognize by > human). > >
> Experimenting with telelenses and professional photo cameras I come to > conclusion what it would be enough to recognize face if it will be > minimum 150 pixel height. So if face is about 20cm height, lenses must > provide zooming for 150pixels/20cm at 60 meters. Dont know how to > convert it to lenses units :) (x-y, f...) > That's not that difficult. With that data and knowing that the pixel size is 0.0022mm you can calculate focal length of an ideal lens: http://www.google.com/search?hl=en&q=60m%2F((200mm%2F150)%2F0.0022mm)+in+mm- that would be ~100mm. The lens for the 2.2um senors should have power not less than 3-4, if it has less (or iris is closed more) you'll have resolution degraded by diffraction (pixel size is just about 3 times the wavelength) And 100 mm is for _ideal_ lens, if one has just 150lp/mm, taking 2 pixels/lp would result in some 150mm focal length. > > Actually, I thought about 2 lenses, but its not nice and general solution. > But its real right now. > I would not agree - sensors are cheaper than lenses. And you are looking for a top performance lens, not just the zoom one for low-res video. The calculations above show that it is a challenge to get the results even with a 120mm fixed-focus lens. I > I supposed if I have such a wide picture from camera I can zoom into > certain regions (for example with your built in Point of View). > Without rotating or tilting. > I need only about 20-30 degrees of view. > With the 120mm lens you will get less than 3 degrees horizontal If you need 150 pixels on 200 mm than 5 MPix sensor will give you 2.5m x 3.5 m field of view (100mm lens). With 120mm - it will be even less. Zoom/no zoom lens, but without rotation platform you will not be able to see anything with full resolution (1.33mm/pixel) outside of that area. to be able to see 30 degrees with resolution of 1.3mm at 60 meters without mechanical rotation you'll need to have 0.5gigapixel sensor. Or about hundred 5 megapixel sensors with individual lenses (still probably cheaper) Andrey
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