Normally I calculate my exposure times for pinhole photography by "guesstimation", especially when I use my converted Gevabox or Agfa Clack.
But sometimes I want to measure the light more securely. When I didn't bring my real light meter, I use the Pocket Light Meter app on my iPhone (also available for android). This app has a minimal ISO setting as low as 0.8 and maximum aperture as high as f/512. This makes this app very usefull for pinhole photography and for using photo paper as a negative. And it is very accurate too. I compared it with my digital camera.
The app is free (with small add in the top of screen) or only $1.00 for the add free version. See for info:
|(screenshots from the app)|
The app has some nice features. It shows also the EV values, if desired. And you can "HOLD" the screen - holding your last reading. You can also take a small snapshot to log the used settings - and add some notes. Here is an example (jpg, 150 KB):
|(sample of a snapshot made with the app)|
The app can also sync with Dropbox to save the snapshots for later. Coming back home you can check the snapshots to see what settings you used when & where: the file names show date & time stamp.
Here you'll find a small test of this app.