iOS, iPad Air)
NDCalc by Boris Nienke on the App Store (iPhone, iPad, iPod touch, iPad Mini, iOS, iPad Air)
by Boris Nienke
Screenshots are german but it's translated to english too.
You know the time without the filter -how long do you need to exp. WITH filter? Sounds easy but tell me quickly how long to exp. with an ND 1.8 if the time without filter is 1/320?
Now you can!
Set Filter and exp. time without the filter and you can see the correct time. In the example above 1/5
Even easier it shows you 5 because this is what you can set on a dSLR. Smaller letters showing you the actual time. For 12500'' it shows, that these are 3h, 28m and 20s.
For times of 4+ seconds you get a countdown button to easily stop longer exposures manually with a remote shutter release with alarm and vibration (if supported).