Bellows Extension Factor Calculator
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.
How to use Bellows Extension Factor Calculator
- Enter the lens focal length.
- Enter the total lens extension.
- Read the exposure compensation in stops.
- Add that compensation to your manual exposure or flash.
Frequently asked questions
Why does macro need exposure compensation?
Extending the lens far from the sensor for close focus spreads the light over more distance, dimming the image. The tool computes the extra stops needed to restore correct exposure.
How is the factor calculated?
It squares the ratio of total lens extension to focal length to find the light loss factor, then converts that factor into stops of compensation.
When can I ignore it?
Through the lens metering already compensates automatically, so this matters mainly with manual flash, external meters, or view cameras where the meter does not see the extension.
What is Bellows Extension Factor Calculator?
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.
Is Bellows Extension Factor Calculator free to use?
Yes. Bellows Extension Factor Calculator is completely free, with no sign-up and no usage limits.
Does Bellows Extension Factor Calculator work in a web browser?
Yes. Bellows Extension Factor Calculator runs in any modern web browser. There is nothing to download or install.
Is my data private with Bellows Extension Factor Calculator?
Yes. Bellows Extension Factor Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.
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