In close up and macro photography you move the lens far from the sensor to focus on tiny subjects, and that extra extension spreads the same light over a longer path so the image gets darker. The bellows extension factor tells you how much light you lose and how much exposure to add back. This calculator uses the standard relation where the factor equals the total lens to sensor distance divided by the focal length, all squared. Enter your focal length and the total extension, which is the focal length plus any bellows draw or extension tubes, and it returns the exposure factor and the number of stops of compensation to dial in. Through the lens metering handles this automatically, but manual flash, external meters, and studio setups need the correction. Without it your macro shots come out too dark. All the math runs in your browser with nothing sent to a server.
In close up and macro photography you move the lens far from the sensor to focus on tiny subjects, and that extra extension spreads the same light over a longer path so the image gets darker. The bellows extension factor tells you how much light you lose and how much exposure to add back.
Yes. Bellows Extension Factor Calculator is completely free, with no sign-up and no usage limits.
Yes. Bellows Extension Factor Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Bellows Extension Factor Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.