Guys, Why does an image of a chicken pass through glass? Not to get to the other side! Real good answer here: http://answers.yahoo.com/question/index?qid=20081113042053AAS9p2i I used WickiAnswers and got: "Because glass is transparent which means light can travel through it. Also because glass is clear. Thats another science question answered by the Wizzo." No, that's not from "Ask Dr. Science"! AZ Build a 120/35mm Lookaround! The Lookaround Book. Now an E-book. http://www.panoramacamera.us > -------- Original Message -------- > Subject: [SPAM] Re: Why does light pass through a lens? > From: Guy Glorieux <guy.glorieux@xxxxxxxxx> > Date: Thu, January 01, 2009 12:09 pm > To: List for Photo/Imaging Educators - Professionals - Students > <photoforum@xxxxxxxxxxxxxxxxxx> > > > > Ahah! So what kind of an image would you get if you drilled a pinhole in > > the center of a glass lens? > > > > Greg > > > > Oooops! A pinholed lens? > I've tried to find funny answer but I just couldn't. So here are some > thoughts. > 1. You'd get an image with a tiny white imageless hole in the center. This > is because the thickness of the glass lens would prevent a pinhole image to > actually form. The reason we use extremely thin brass shim in which to drill > the pinhole is to ensure that the vignetting arising from the thickness of > the shim is reduced to a minimum. > 2. If you could design an extremely thin glass lens and drilled a pinhole > in the center, then you would have two images that should normally perfectly > overlap since the lens focal length would be identical to the focal length > of the pinhole. However, since each lens will have their own distortion > features, the pinhole and the lens will not produce identically configured > images. > 3. Evidently, the pinhole image would be washed out completely by the lens > image since the effective aperture of the pinhole would be far less than > that of the lens. > Some have reversed the question: what if you put a lens in from (back) of a > pinhole? I'll let you figure that one out, if you can... -:) > Happy New Year! > Guy
