Archived posting to the Leica Users Group, 1997/02/18
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I tried piercing a hole in a Leica bodycap but the diameter of the image circle was only the breath of the negative. What should I do?? - --Adi At 10:40 PM 17-02-97 EST, you wrote: >Good Day! > >I just looked through some of my older Zeiss microscopy catalogues, and >have read Dr. Abbe's theory of numerical aperture. > >The numerical aperture of any lens is calculated by dividing the focal >length of the lens by the RADIUS of the physical aperture--1/2 the >diameter of the hole, in mm. >in regards to the pinholes. > >The focal length of the pinhole has nothing to do with its apeture, but >rather it is the distance from the film plane to the aperture. > >So: a pinhole located 50mm from the film plane IS a 50mm lens, a pinhole >located 100mm from the film plane is a 100mm lens etc. > >Apertures at 50mm extension: > >0.25mm hole--f400 >0.5mm hole--f200 >1mm hole--f100 > >f100 at 50mm extension, should yield depth of field of approx 2" to >infinity. > >I hope this helps all you "Pinholers" out there. > >Sincerely, >Thomas P. Myro >Photology@juno.com > >