Determining the DOF for an image takes complicated math.
DOF stands for depth of field, and it's a bit of a complicated concept. When taking a picture, only certain parts of the image will be in focus, depending on where the lens is aimed. For example, a shallow depth of field used on an image of a cat in a field would show a cat in full focus, and the field behind it would be blurry. Finding out the depth of field for your SLR camera is a bit tricky, and involves some complex math.
Instructions
1. Determine whether your camera has an APS/APS-C sensor or a full-frame sensor by checking the owner's manual of your camera. Find out what size lens you have by looking at the number on the side of it, then determine the aperture your camera is set at by looking at the display on the top of the camera.
2. Determine the hyperfocal distance by multiplying the size of the lens by itself using the calculator. For example, 50mm times 50mm equals 2,500.
3. Multiply the aperture setting on the camera times the type of sensor you have, using the number 0.019948 for an APS/APS-C sensor and 0.02501 for a full-frame camera. For example, 2.8 times 0.019948 equals 0.0558544.
4. Divide the result from step 2 by the result from step 3 to get the hyperfocal distance in millimeters. Multiply that number by 0.0393700787 to convert the result to inches, then divide that number by 12 to find out the number in feet. For example, 2,500 divided by 0.0558544 equals 44,759.2311mm; 44,759.2311mm multiplied by 0.0393700787 equals 1,762.1744527 inches; 1,762.1744527 divided by 12 equals 146.85 feet.
5. Measure the distance between the end of the camera lens and the object using the tape measure and record this number in feet.
6. Determine the near point for the object, which is the closest amount that the object will be in focus, by first multiplying the result from step 4 by the distance recorded in step 1. For example, 146.85 multiplied by 10 feet equals 1,468.5 feet.
7. Convert the size of the lens from millimeters into feet by multiplying it by 0.0393700787, then dividing by 12. For example, 50mm multiplied by 0.0393700787 equals 1.968503935 divided by 12 equals 0.164042 feet.
8. Subtract the result from step 7 by the number from step 5. Add the result to the result from step 4. For example, 0.164042 feet plus 10 feet equals 10.164042 feet; added to 146.85 feet, the result is 157.014042 feet.
9. Divide the result from step 6 by the result from step 8 to get the near point in feet. For example, 1,468.5 feet divided by 157.014042 equals 9.35 feet, so the near point of the object is 9.35 feet.
10. Determine the far point of the object by first multiplying the number from step 4 by the number from step 5. For example, 146.85 multiplied by 10 feet equals 1,468.5 feet.
11. Subtract the number from step 7 by the number from step 5. Subtract that number from the number in step 4. For example, 10 feet minus 0.164042 feet equals 9.835958 feet; 146.85 feet minus 9.835958 feet equals 137.01 feet.
12. Divide the result from step 10 by the result from step 11 to get the far point of the object. For example, 1,468.5 feet divided by 137.01 feet equals 10.72 feet.
13. Determine the DOF for the object by subtracting the result from step 9 by the result from step 12, to get the total depth of field in feet. For example, 10.72 feet minus 9.35 feet equals 1.37 feet.
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