| 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 |