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Focal Distance Formula:
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Focal distance is the total distance from the optical center of a lens to the focal point, calculated as the sum of the focal length and any extension used. It's a crucial parameter in photography and optics for determining focus and image formation.
The calculator uses the focal distance formula:
Where:
Explanation: This simple additive formula combines the lens's natural focal length with any extension tubes or bellows used to achieve proper focus.
Details: Accurate focal distance calculation is essential for macro photography, telescope setup, microscope configuration, and any optical system where precise focusing is required.
Tips: Enter focal length and extension in millimeters. Both values must be positive numbers. The calculator will sum them to give you the total focal distance.
Q1: What's the difference between focal length and focal distance?
A: Focal length is an inherent property of the lens, while focal distance is the total working distance including any extensions.
Q2: When would I need to use extension in photography?
A: Extension tubes are commonly used in macro photography to achieve closer focusing distances and greater magnification.
Q3: Does adding extension affect image quality?
A: While extension allows closer focusing, it may reduce the amount of light reaching the sensor and potentially affect depth of field.
Q4: Can I use negative extension values?
A: No, extension values represent physical distance and must be positive. Negative values are not physically meaningful in this context.
Q5: How precise should my measurements be?
A: For most photographic applications, measurements to the nearest millimeter are sufficient, though precision optics may require more accurate measurements.