Assertion: shutter curtain | /r/CapableOf | block the light
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Source sentences:
text: It is even more important for mirrorless cameras to have EFCS than DSLRs, because the first mechanical curtain is already open, so if the camera is not able to start the exposure electronically, the shutter curtain will have to be closed first to block the light and reset the sensor, then reopen again to start the exposure.