> I just read the article G. Penate referred to about calculating exposures, > by calulating the f stop of the pinhole and trying to devine the exposure by > counting f stops from a referral point. It doesn't need to be that hard. > 1. Measure the pinhole to film distance and divide by 22. That gives you the > diameter of f22 for that distance. > 2 Then calculate the area of this f22 aperture by multiplying half the > diameter x half the diameter x 3.14. > 3.Then measure the diameter of the pinhole, using the same measure as you > did before, inches or millimeters both times. > 4.Then calculate the area of the pinhole using the same formula. > 5. Then divide the area of the pinhole into the area of the F22 aperture you > calulated, and use the result to multiply times the metered exposure at f22. > > At an optimal pinhole to film distance of three inches, for instance, the > multiplier is about 120. If the metered exposure at f22 is 1/10 second, the > calculated metered exposure for the pinhole would be 12 seconds. You can > drive yourself batty trying to work it through the f stop comparison method.
The beauty of math is you can get to "Rome" using many "roads". The example I give is using "sunny-16", so I ask you to find the number of stops separating f/16 to the f/stop of your pinhole, in the case of the example is 9. Then I ask you to double the exposure time 9 times, which is the same as finding 2 to the power of 9 or 2^9 = 512 that 512 is the MULTIPLIER, again in the example the exposure using "sunny-16" is f/16 and 1/6secs then the exposure for the pinhole would be 1/6 * 512 or 512 / 6 = 85 which is the same thing as doubling 1/6 9 times. The idea of doublings is that you are just "adding", sometimes I am afraid of suggesting anything that has powers or roots because I want the explanation to be as down to basics as possible. Nevertheless, anybody that has at least high school should know that doubling the number two "n" number of times is equal to 2^n. Guillermo
