I have a pinhole adapter. It’s actually for a Canon FD mount, but I have an FD-M mount adapter so I can use it on my digital camera. Adapter on adapter.
According to the supplier the pinhole has the following specifications:
- F-Stop: F204
- Hole: 0.22mm
- Angle of view: 52º
So, naturally, I wondered whether this configuration would produce optimal images. By optimal, I really mean in focus.
There are two variables to play with in a pinhole: [1] the size of the hole [2] the distance between the hole and the sensor plane. The size of the hole is fixed; drilled by the manufacturer at 0.22mm. As well, the distance is fixed, but I don’t know what that is and thus it needs to be calculated. I completed the following: [1] distance from sensor plane to flange (lens mount) [2] height of FD-M Adapter [3] height of pinhole adapter. This works out to distance = [1] + [2] + [3] or 28.4 + 11 + 3 = 42.4 mm.
Using the formula [1] to calculate the pinhole size I can see if what I have is close enough. The formula where r = pinhole size is r = SQRT (wavelength of light * magic constant * focal length); r = SQRT (0.00055 * 1.9 * 42.4) = 0.290.
That is the optimum pinhole size for the focal length (42.4) is 0.29 mm. What I have is 0.22 mm. So, will this difference be observable?
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