If you do any darkroom work, you probably regularly print contact sheets to peek at the positive versions of your B&W negative film strips. Did you know that your iPhone can be used as a quick an easy tool for this same purpose?
To do this, simply go to Settings->General->Accessibility->Triple-click Home, and then select the Invert Colors option:
Once this is set, all you have to do is press the home button three times in rapid succession in order to invert all the colors on your screen.
Now, all you need to do is put your black-and-white negatives up to a monitor or down on a lightbox…
…and then boot up your favorite camera app and point your iPhone at the negative:
Voila! Instant negative viewing without having to waste time and photo paper.
Here’s a great video version of this same tutorial by photographer Nate Matos:
This tip will work for other phones and devices as well, as long as you can find a way to invert the colors of your display. We hear that it also works well with a loupe if you need a closer look at the details of your images.