To calculate the correct exposure equivalence based on an initial shutter speed aperture and ISO settings.
You can use the calculator with ND filter. Determine how to make 1000 times longer photos for example.
Two of the three parameters can be blocked the last parameter is determined automatically.
The minimum and maximum speed can be set it goes the same for aperture and ISO to be specific to your device.
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photo ND filter long exposure exposure calculator
Advanced settings that allow you to configure all speeds apertures and sensitivities manually.