Exposure
Subject Motion Blur Calculator
Project subject travel during exposure onto sensor pixels.
Enter the exposure values
For Subject Motion Blur, keep units and the camera, meter, frame, or lighting reference attached to every entry.
The exposure result will appear here with supporting checks.
The exposure question answered by Subject Motion Blur Calculator
Project subject travel during exposure onto sensor pixels.
The calculator reports projected blur from Subject speed, Subject distance, Focal length, Pixel pitch, Shutter time. Treat Subject speed, Shutter time, and projected blur as one Subject Motion Blur case. Mixing Subject speed from one frame with Shutter time from another would answer a different question.
Use it to connect real subject speed with an approximate number of sensor pixels.
Recording the inputs behind projected blur
Record Subject speed and Shutter time with their displayed units. For Subject Motion Blur, retain any ISO convention, sensor or lens reference, meter constant, pixel basis, and clock date that gives Shutter time its intended meaning.
Identify whether Subject speed came from EXIF, a handheld meter, an equipment specification, or a field measurement; those sources may use different conventions. Note the source beside the saved result.
How Subject Motion Blur Calculator calculates its result
Project subject travel during exposure onto sensor pixels.
Subject Motion Blur Calculator evaluates the entered values at full precision; rounding is reserved for the displayed projected blur. Predict the direction of projected blur before calculating: changing Subject speed alone should produce a physically explainable response.
Checking subject speed with the starting values
For Subject Motion Blur, run the published values unchanged and save projected blur. The supporting values beneath projected blur expose the ratio, stop change, timing quantity, or sensor measurement used to check this particular model.
Then change only Shutter time. Return Shutter time to its published value afterward and confirm the original projected blur appears again. Changing only Shutter time isolates its effect; moving every Subject Motion Blur input together would conceal which assumption caused the difference.
Where Subject Motion Blur stops
The model assumes motion perpendicular to the optical axis and a small field angle.
Projected blur alone cannot decide whether the resulting blur, highlight placement, noise, optical behavior, or timing serves the intended photograph.
Reading projected blur in stops and ratios
When interpreting projected blur, remember that one stop doubles light, time, or ISO but changes an f-number by the square root of two. The labels in Subject Motion Blur Calculator determine which version belongs in the equation.
When Subject speed changes, state whether projected blur rises or falls and whether that direction adds or removes recorded exposure. That direction check prevents a sign error when the displayed scale for Subject speed runs opposite to the underlying physical opening, time, or margin.
Verifying projected blur against the camera or meter
Compare projected blur with the camera display, raw histogram, meter, stopwatch, lighting test, or known reciprocal-rule case that applies. If the independent check disagrees with projected blur, inspect Subject speed, Shutter time, and their units instead of averaging incompatible answers.
The Camera Panning Speed Calculator provides a nearby exposure check when the next question changes. Carry Subject speed into the neighboring calculation only when it still refers to the same frame, light, camera, and exposure plan.
Translating projected blur to available settings
Projected blur may fall between the full-, half-, or third-stop choices available on the camera or lens used for Subject Motion Blur. Keep the unrounded projected blur for comparison, then choose the available setting that protects the photographic priority.
If Shutter time reaches a flash-sync, aperture, ISO, shutter, stabilization, or motion limit, move the remaining stop change to an available control and rerun Subject Motion Blur.
Saving a reproducible Subject Motion Blur case
Save Subject speed, Subject distance, Focal length, Pixel pitch, Shutter time, projected blur, units, date, camera or meter reference, and the calculator name. Mark measurements separately from assumptions.
For Subject Motion Blur, when the light, framing, subject, or equipment changes, keep the earlier projected blur as a labeled baseline. A later Subject Motion Blur version should differ because Subject speed, Shutter time, or another recorded input changed—not because an undocumented correction was applied.
Measurement boundary for Subject Motion Blur
Define exactly where Subject speed begins and ends and what the entered Shutter time includes. For Subject Motion Blur, distinguish a value measured at the subject, derived from reflected light, read from the camera, or taken from an equipment specification.
List deliberate exclusions beside projected blur. An omitted stabilization allowance, motion pattern, transmission loss, clipping rule, changing light level, or calibration of Shutter time can alter how this output should be interpreted.
For Subject Motion Blur, apply one boundary to both the practical test and the saved Subject Motion Blur record. If Subject speed already contains a filter, crop, calibration, safety, or correction allowance, do not add that same adjustment a second time when reporting projected blur.
Questions about subject motion blur calculator
What does Subject Motion Blur Calculator return?
It returns projected blur from Subject speed, Subject distance, Focal length, Pixel pitch, Shutter time using this relationship: Project subject travel during exposure onto sensor pixels.
Which entry should I verify first?
Verify Subject speed and its unit, then confirm that every other value describes the same exposure setup.
What is the main limitation of this result?
The model assumes motion perpendicular to the optical axis and a small field angle.