Making a DOF ring for a geared focusing knob (for any camera with geared focusing knob) Making a DOF calculator knob min f-Number and delta on friction knob for Arca Swiss F-line cameras Change c as you wish c: circle of confusion (mm) MF 0.05 4x5 0.089 5x7 0.12 8x10 0.18 10x12 0.24 N = 10^(1/2*log(2)*Av) delta: distance on the rail (mm) delta = 2*c*N delta = 2*c*10^(1/2*log(2)*Av) There are a couple of ways to measure or derive D: delta on ring/delta. For example, place a strip of paper on the focusing knob and glue ends together. then mark 0 on the strip and mark a fixed reference point somewhere close to but not on the focusing knob. Then rotate the knob and until you advance to delta at N = 45 according to the table below. Here given c = .089 mm, delta = 8.1mm at N = 45. So advance the rear standard 8.1mm then mark on the strip. Now calculate D: delta on ring/delta = (delta on ring at N = 45)/delta For example, I've got 37.6mm for delta on ring at N = 45. delta on ring (mm) at N = 45 (mm) 37.6 delta at N = 45 (mm) 8.1 D: delta on ring/delta 4.67 Aperture Value Av f-number N delta (mm) 4x5 delta on ring (mm) scale lines delta (mm) MF delta (mm) 5x7 delta (mm) 8x10 delta (mm) 10x12 -11.0 45 -8.1 -37.6 5.5 -4.5 -10.9 -16.3 -21.7 -10.7 40 -7.2 -33.5 5.5 -4.0 -9.7 -14.5 -19.4 -10.3 36 -6.4 -29.8 5.5 -3.6 -8.6 -12.9 -17.2 -10.0 32 -5.7 -26.6 5.5 -3.2 -7.7 -11.5 -15.4 -9.7 29 -5.1 -23.7 5.5 -2.9 -6.8 -10.3 -13.7 -9.3 25 -4.5 -21.1 5.5 -2.5 -6.1 -9.1 -12.2 -9.0 23 -4.0 -18.8 5.5 -2.3 -5.4 -8.1 -10.9 -8.7 20 -3.6 -16.7 5.5 -2.0 -4.8 -7.3 -9.7 -8.3 18 -3.2 -14.9 5.5 -1.8 -4.3 -6.5 -8.6 -8.0 16 -2.8 -13.3 5.5 -1.6 -3.8 -5.8 -7.7 -7.7 14 -2.5 -11.8 5.5 -1.4 -3.4 -5.1 -6.8 -7.3 13 -2.3 -10.6 5.5 -1.3 -3.0 -4.6 -6.1 -7.0 11 -2.0 -9.4 5.5 -1.1 -2.7 -4.1 -5.4 -6.7 10 -1.8 -8.4 5.5 -1.0 -2.4 -3.6 -4.8 -6.3 9 -1.6 -7.5 5.5 -0.9 -2.2 -3.2 -4.3 -6.0 8 -1.4 -6.6 5.5 -0.8 -1.9 -2.9 -3.8 -5.7 7.1 -1.3 -5.9 5.5 -0.7 -1.7 -2.6 -3.4 -5.3 6.3 -1.1 -5.3 5.5 -0.6 -1.5 -2.3 -3.0 -5.0 5.7 -1.0 -4.7 5.5 -0.6 -1.4 -2.0 -2.7 -4.7 5.0 -0.9 -4.2 5.5 -0.5 -1.2 -1.8 -2.4 -4.3 4.5 -0.8 -3.7 5.5 -0.4 -1.1 -1.6 -2.2 -4.0 4.0 -0.7 -3.3 5.5 -0.4 -1.0 -1.4 -1.9 0 6 0.0 0 5.5 0.0 0.0 0.0 0.0 4.0 4.0 0.7 3.3 5.5 0.4 1.0 1.4 1.9 4.3 4.5 0.8 3.7 5.5 0.4 1.1 1.6 2.2 4.7 5.0 0.9 4.2 5.5 0.5 1.2 1.8 2.4 5.0 5.7 1.0 4.7 5.5 0.6 1.4 2.0 2.7 5.3 6.3 1.1 5.3 5.5 0.6 1.5 2.3 3.0 5.7 7.1 1.3 5.9 5.5 0.7 1.7 2.6 3.4 6.0 8 1.4 6.6 5.5 0.8 1.9 2.9 3.8 6.3 9 1.6 7.5 5.5 0.9 2.2 3.2 4.3 6.7 10 1.8 8.4 5.5 1.0 2.4 3.6 4.8 7.0 11 2.0 9.4 5.5 1.1 2.7 4.1 5.4 7.3 13 2.3 10.6 5.5 1.3 3.0 4.6 6.1 7.7 14 2.5 11.8 5.5 1.4 3.4 5.1 6.8 8.0 16 2.8 13.3 5.5 1.6 3.8 5.8 7.7 8.3 18 3.2 14.9 5.5 1.8 4.3 6.5 8.6 8.7 20 3.6 16.7 5.5 2.0 4.8 7.3 9.7 9.0 23 4.0 18.8 5.5 2.3 5.4 8.1 10.9 9.3 25 4.5 21.1 5.5 2.5 6.1 9.1 12.2 9.7 29 5.1 23.7 5.5 2.9 6.8 10.3 13.7 10.0 32 5.7 26.6 5.5 3.2 7.7 11.5 15.4 10.3 36 6.4 29.8 5.5 3.6 8.6 12.9 17.2 10.7 40 7.2 33.5 5.5 4.0 9.7 14.5 19.4 11.0 45 8.1 37.6 5.5 4.5 10.9 16.3 21.7 film size CoC (mm) delta (mm) at N = 45 delta (mm) on ring at f-number N = 45 MF 0.05 4.5 21.1 4x5 0.089 8.1 37.6 5x7 0.12 10.9 50.7 8x10 0.18 16.3 76.0 Printing the strip Set the printer scale option based on above delta at N = 45 Example: Printing with default setting gives delta on ring equal to mm at N = 45: 115.2mm Delta on ring at N = 45: 37.6mm For 4x5 strip, calculate %rescaling factor = 100*37.6/115.2 The calculation gives about 32.6%. So set the rescaling factor to 32.6% of the default print size setting. Then print and check if a value on printed scale matches to the actual value of delta on tension knob for a given f-number N. default print scale at some N delta on ring at N = 45 %rescale factor 115.2 37.6 32.6

??? 00/06/24
?? Masayoshi Hayashi