<p>You need three things.<br>
The first is, obviously, a dark /ND/ filter - or better, a set of them. I have a 4, 6 and 10 stop filters in my bag all the time.<br>
The seciond would be to know how to calculate the correct exposure. There are a lot of applications for that, but you can also calculate it. For example, if your camera shows you recommended exposure of 80ms without the filter, that would be 1000x more with an 10 stop filter. So you need 80 seconds<br>
The third think would be a programable cable release in order to get the well-calculated long exposure.</p>
<p>Thats it. Happy shooting</p>
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