Photo Tools is a tool for amateur and professional photographers.
With this application you can do this things:
- Calculate the exposure time in a long exposure night photography.
- Calculate the hyperfocal distance in a photograph.
- Shooting stars as points rather than traces

Just enter the data and get results quickly and easily.

One of the necessary data is the circle of confusion. This is a different number for each manufacturer and type of camera. Nikon DSLRs generally have a value of 0.020 and 0.019 for Canon but for sure the value of your camera visit this page:
http://www.dofmaster.com/digital_coc.html
You can also do a search on the web to get this value.