A Litte Garden

Viewfinder cameras such as Minox GT-E or Minox B are scale focusing cameras, you have to estimate the distance and set the distance scale on these cameras accordingly.There are many ways to determine the object distance, from eyeballing to using a separate range finder.Do you know that you can make a rangefinder for you Minox subminiatures or Minox 35mm for next to nothing ?All rangefinder has two windows, separated by a distance, called the baseline. The longer the baseline, the more accurate the ranger finder.One day, I suddenly realized that a pair of human eyes is a natural rangefinder, its base line is between 6cm to 8cm. Why can't I use my eyes as a rangefinder to determine the focusing distance of viewfinder cameras such as Minox GT-E or Minox B ?I performed an experiment: I held a ruler with right hand at arms length, first closed my right eye, used only my left eye to align one end of the ruler with a line or an edge of an object, then close my left eye, open the right eye, I noticed that the line now aligned at a distance X to the right of the edge. I noticed that the further the object, the greater the displacement.After some simple calculation I found that the image displacement X is given by the following formula :X =E*(D-A)/D; where E is separation of eyes D is object distance, A is arm's length.For example let Eye separation =7 CM, Arm's length=60 CM ;D=1 M X= 2.8 CMD=1.2M X= 3.5 CMD=1.5M X= 4.2 CMD=1.7M X= 4.5 CMD= 2M X= 4.9 CMD=2.5M X= 5.3 CMD= 3M X= 5.6 CMD= 4M X= 6.0 CMD= 5M X= 6.2 CMD=10M X= 6.6 CMD=20M X= 6.8 CMDistance Marking1 M 2.8 CM1.2M 3.5 CM1.5M 4.2 CM1.7M 4.5 CM2M 4.9 CM2.5M 5.3 CM3M 5.6 CM4M 6.0 CM5M 6.2 CM10M 6.6 CM20M 6.8 CMI drew these lines on the back of a piece of calling card for use with Minxo GTE I also drew the eye-rangefinder marks at the back of my Minox C.A simpler method of drawing this eye-rangefinder marks is the following: mark 1 m 1.2m 1.5m, 2m,2.5m, 3m,4m etc on the floor,with ruler level at arm's length, read off the ruler at points corresponding to the distances. Then mark these on a piece of calling card or at the back of Minox 8x11. ( whichWhen use, I hold the Minox or calling card leveled with my right hand at arm's length, align one end with left eye, use right eye to read the distance. When object fall between two marks, set distance proportionally.For example, if the object lies between 1.7 M and 2M, set distance at 1.8MAfter some practice, I now can see two images of calling card from two eyes and read off the distance without closing one eye.Try it, it works.