If you've ever photographed a screen, or painting, or any flat surface before, and wanted to keep the camera and subject on the same plane, there's a pretty straightforward way to measure the angle of the subject then match it on the camera, simply using your iPhone.
The backstory
This is a pretty old shoot, and I meant to post this long ago but never did. At the beginning of the year, I photographed a setup in my studio to put on the front page of ApertureExpert.com. I wanted a variety of Mac, iOS, cameras and so-on in the scene, and I wanted to be able to replace the images in the screens easily.
Here's the basic behind-the scenes setup.
The setup… one big light and lots of gear. A few gobo cards ended up moving in to block a few untoward reflections as well.
Getting the camera tilted at the same angle as the computer screen was proving to be a little tricky though. In the resulting shot, the screen looks straight on—and that was the point. But I couldn't shoot the camera straight on because I wanted a slightly angled view on the rest of the setup. So how do you measure the tilt of the screen and camera and make them match? The Compass app!
Compass app to the rescue! Just slide to the left from the compass screen to reveal the digital level.
The digital level is just a swipe away from the built-in Compass app in iOS. I was able to hold the iPhone against the computer screen as you see in the shot above to measure it's angle, and then lean it against the back of the camera, tilting it until I got the same 6˚ tilt. Cool huh?
Here's the resulting shot, with and without a red box drawn in Photoshop to show how true the shot was. It wasn't 100% pixel perfect, but it was very very close, and of course good enough for my needs.
Here's the master photo, before retouching. See how straight that Mac screen looks?
Verified! Same image as above, with a red line around the screen. If you look reeeaaaalllly close you'll see it's not completely perfect. But it was really, really close.
The result
Here's how the final image came out. This is fully retouched, with images dropped into the screens. Pretty cool trick there, too. The screen images are smart objects, angled (in the case of the iPad screen) with reflections added, etc. to the smart object. I can replace the photo behind it without having to redo any of the "make it look real" work. Neat!
The landing page of ApertureExpert.com (which of course is about to change to The Photos Expert, so enjoy it while it's up! ;-)
That's all! Next time you're trying to align your camera with another object to make your lines true, break out the Compass app and swipe over to the digital level. It could save loads of guesswork, and retouching later!