Last updated: October 1, 2026.
The calculators, guides and data on LensMath are provided for general informational and educational purposes only. We work to keep the formulas accurate, but we make no representations or warranties of any kind, express or implied, about the accuracy, completeness or suitability of the results for critical or commercial use.
What the results do and do not include
Our Speed Booster & Effective Aperture Calculator assumes ideal optics, so its results are theoretical values. They do not account for:
- light absorbed by the glass in a specific adapter (real exposure is measured in T-stops)
- vignetting, edge softness or other optical quirks of a particular lens or adapter
- video crop modes or other settings that change your camera’s effective crop factor
Camera crop factors in our list are typical values and may differ from your exact model or shooting mode. You can read the formulas and examples in our guide to speed booster effective aperture, and the full method on our methodology page.
Use at your own risk
You use LensMath at your own risk. To the fullest extent permitted by law, LensMath and its owner are not liable for any loss, damage, ruined exposures, missed shots or equipment problems arising from use of this website or reliance on its results. Always check your exposure, focus and gear settings in real shooting conditions, and follow the manufacturer’s instructions for your equipment.
External links
Some pages link to external websites for reference. We do not control their content and are not responsible for it.
Questions or corrections
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