Archived posting to the Leica Users Group, 2002/03/06
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 1:17 PM -0500 3/6/02, B. D. Colen wrote: >Okay, all you Optigods, a question for you: > >If a + diopter is a magnifier, wouldn't a +1.25 diopter do the same thing >that the new $229 Leica M 1.25 Viefinder magnifier does - for $73, without >protruding from the back of the camera, and without the really cute little >chain and carrying case? > >I am, of course, being a bit facetious - but the question is absolutely >serious. If they aren't the same thing, what is different about them in >terms of function? > >Thanks A + diopter may be termed a 'magnifier', but is is usually only a simple positive lens (Elpros and some other 'close-up lenses' have a weak negative element glued onto the strong positive element to correct chromatic aberrations). This changes the focal length of the optical system, making it shorter, so that at the same extension from the imaging plane it will focus on closer objects. In a camera eyepiece, it will correct the image so that the person looking through the viewfinder, whose eyes normally focus beyond infinity, can now see clearly in the normal range. Camera viewfinder images are usually projected at a distance of 1-2m. The important point here is that it changes the distance at which the viewfinder image is projected. The 1.25 viewfinder magnifier is a small optical system which acts like a tele-converter, also known as a Barlow lens. This also changes the focal length of the system, but it allows the eyes to focus at the same distance to see the image through the viewfinder. - -- * Henning J. Wulff /|\ Wulff Photography & Design /###\ mailto:henningw@archiphoto.com |[ ]| http://www.archiphoto.com - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html