NDCalc2

Screenshots are german but it's translated to english too.
This is a completely rewritten Version of NDCalc - now called NDCalc2. It's all new with these great features:
- build for iOS7
- supports the 4" Screens of iPhone5/s/c
- supports retina
- Much more comfortable selection of shutter speed and NDFilter (no wheel control)
- Multi-Select! Finally! You can switch to Multi-Select-Mode with a single tap in the toolbar if you are a ND-Filter-Stacker like myself :) Just activate Multi-Select-Mode and tap on any Filter you have stacked to the lens for really long exposures.
- Add your own Filters! Finally! You own a filter which is not listed in the default list? Just add it by f-stops, ND-Value or Factor.
- Delete Filters. Just delete all filters you don't own and make selecting filters much more convenient
- Reorder Filter. Order the Filter-List as you like it. Bring up the most used filters to the top of the list.
The core function is still the same as NDCalc:
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).