Is this lens's image circle geometrically large enough?

Answer

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Geometry, not a vignetting verdict

Image-circle arithmetic can show whether a declared circle is large enough for a sensor rectangle and a requested shift. It cannot show whether a particular lens and adapter will vignette, clear physically, stay sharp, or maintain coverage at every aperture. Use the geometry to expose margin, then verify the real system before an important shoot.

A 36×24mm sensor needs a 43.27mm geometric circle without shift. Add 10mm vertical shift and the requirement becomes about 56.85mm. A declared 44mm circle can barely exceed the unshifted sensor diagonal but cannot cover that shifted rectangle. Even a positive margin needs an actual corner and aperture test because usable coverage is not only a circle calculation.

This result models the values you entered. It cannot see the scene, verify focus or movement, predict camera-specific processing, or guarantee the final photograph. Use it as a stated starting point, then check the important subject area in a test frame or proof.

Make one controlled test with the important variable held constant. Inspect the subject detail, motion, highlights, and intended output, then adjust the setting that protects the priority you named.

FAQ

Does a positive image-circle margin guarantee no vignetting?

No. It only compares declared geometry. Optical falloff, adapter mechanics, aperture, and lens behaviour can still affect the image.

Is this a guarantee?

No. The result is bounded by the inputs and assumptions shown on the page. It is designed to support a better next decision, not replace a test, measurement, proof, or professional judgement where one is needed.

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