How slow can you go with daytime long exposures?
Most of the time you won’t have to make these calculations yourself, as the camera will automatically compensate for the filter in front of the lens. Simply switch to Aperture Priority (Av) mode, dial in your chosen aperture, and your camera will set the shutter speed accordingly.
However, your camera is usually limited to a maximum shutter speed of 30 seconds in this mode, and very strong ND filters, such as the inky-black Lee Big Stopper, block so much light that exposure times may need to be much longer.
The solution here is to switch to Bulb mode. In this mode you control how long the shutter stays open, using either a programmable or lockable remote release.
Thankfully, gone are the days when you needed to scrawl out calculations on the inside of a 35mm film box; there are a range of smartphone apps on the market that will do all this for you (see below) and even count down the exposure too.
If you notice discoloured streaks or patches on an image taken using a long exposure it’s likely to be the result of light leaking into the camera, either through a gap around an incorrectly positioned filter or (more likely) through the viewfinder eyepiece (remember to cover this, no matter how low the light levels).
If skies look featureless and blown out, and that’s not the effect you’re after, fit an graduated ND filter in addition to the solid ND.
Position the dark section over the sky and the clear section over the sea or land – and be sure to factor this additional filter in if calculating the exposure manually.
PAGE 1: Using ND filters for daytime long exposures
PAGE 2: How slow can you go in your daytime long exposure?
PAGE 3: Calming the waters
PAGE 4: The best way to set up your camera for daytime long exposures
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