How to Calculate Distance and Exposure Time

How to Calculate Distance

In order to calculate the distance your camera needs to be from the object you are trying to capture, you need the dimensions of the photo paper you are join to use, the dimensions of the camera, as well as the height of the object you are trying to capture.

ALL OF THESE DIMENSIONS SHOULD BE IN INCHES. CONVERSION TO FEET CN BE DONE AT THE END.

Measure the distance from the side of the aperture to the side of the photo paper (the blue line in the image below). This is the Focal length, which will be represented by f.

Next, if the object is tall and you want to capture its height, find the height of the photo paper you are going to use. However, if you would rather capture the length of an object (such as a longer building) use the width of the photo paper. (they both are the green line). This will be represented by i

Next, find the height (or width, depending on which you chose for i ) of the object you are going to take the picture of (the red line). If you were to take the picture of a group of people, use the height of the tallest person. This is represented by the O.

Once you've got these, you will be able to find d, or the distance, in inches. Since i/f =o/d, you can find d with the formula (O x f)/i

[(O times f) divided by i]

The distance will be in inches, and you can convert it to feet and remaining inches (if any) by dividing by twelve.

How to Calculate Exposure Time:

Follow these instructions to know exactly how many seconds you should keep the aperture open and exposed to sunlight. My camera needed 12.8 seconds, however, the different dimensions and sizes of the photo paper affect the outcome.