셔터 속도: HDR 및 저조도 촬영
Shutter speed is the time each pixel integrates light during an exposure. Longer exposures collect more photons but allow more image motion. For a robotics camera, choose an exposure that preserves the required feature detail while providing enough signal for the algorithm.
Motion blur and shutter timing
Motion during exposure spreads a feature across pixels. For approximately uniform transverse motion, smear at the sensor is object speed multiplied by exposure time and magnification. Shorter exposure or a short light pulse can reduce that smear before capture. A strobe limits the effective exposure only when it dominates ambient light and the relevant pixels integrate the pulse.
After capture, classical deconvolution can reduce some known blur. Its effectiveness is limited by noise and information lost in the exposure. Learned deblurring methods can use paired images, synthetic blur, video, or self-supervised training. They do not all require stationary ground-truth images from the same camera, but each model needs validation on the intended scene and camera output.
Motion blur differs from rolling-shutter skew. Skew occurs because rows integrate at different times. A global shutter removes that timing difference, while motion during the common exposure can still blur the image.
Noise, gain, and low light
Temporal noise is the variation between repeated measurements at a pixel under the same conditions. Photon shot noise, dark-current shot noise, and read noise contribute to it. Longer exposure can improve signal-to-noise ratio when the scene allows it, but also increases motion blur and dark signal.
Digital gain multiplies the already digitized signal and noise together. It does not improve input-referred signal-to-noise ratio. Denoising can improve a task result, but may also remove texture or introduce artifacts. Test exposure, gain, and processing together using the features the system must detect.
HDR capture takes more than a shutter click
HDR systems may combine different exposures, equal-exposure bursts, or multiple sensor readouts. A phone's shutter sound or screen animation does not reveal the integration time or acquisition sequence. Frames may already be buffered before the tap. Use documented timing, timestamps, or a controlled timing test when acquisition delay matters.
References and related guides
- EMVA 1288, Release 4.0 Linear: sensor signal and noise definitions.
- Self-Supervised Linear Motion Deblurring: an example of training without paired sharp ground truth.
- Hasinoff et al., Burst Photography for High Dynamic Range and Low-Light Imaging on Mobile Cameras: equal-exposure burst processing.
- Motion blur and camera noise.