ImageReasonExposure, Dynamic Range, and Low Light
What ND filter gets me to my target shutter time?
Enter a baseline shutter and a target shutter to see the ideal attenuation in stops, then compare it against a real filter option and the residual it leaves.
Answer
Want to learn more? How ImageReason Tests Calculations and Local Analysis
Explore results
Calculate to see the time scale.
| Filter | Result shutter | Residual |
|---|
Calculate a result to generate a copyable plan.
The stop difference is the real calculation
An ND filter reduces light so the shutter can stay open longer at the aperture and ISO you want. The useful calculation is the stop difference between a tested baseline and a target time, not a generic filter label. A 1/125-second baseline needs about 6.97 stops to reach one second. A six-stop filter reaches about half a second, leaving almost one more stop. That remaining difference can matter when the target is a deliberate motion duration rather than merely "long exposure."
Choose the target shutter from the subject motion you want to test, then calculate the ideal attenuation. Compare the nearest filter options and keep the residual visible. A stronger filter may force a longer exposure than intended; a weaker filter may require an aperture or ISO change. Very long times can cross camera timing limits and film can introduce reciprocity behavior. The filter calculation does not know color cast, flare, moving light, or camera processing, so make an unfiltered composition and focus check before adding the filter.
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
- Can I use the nearest whole-stop filter?
- Yes, if you also account for the displayed residual stop difference. The filter label alone does not guarantee the target shutter.
- Why no universal best setting?
- There is no universal best setting because the relevant tradeoff changes with the subject, light, movement, output, and the part of the image that matters. This tool makes the stated tradeoff visible rather than hiding it behind a generic recommendation.