Safety Shift has been around for a long time but almost every Canon user I talk to has no idea what it is or has ever used it.
That’s a shame. Because Safety Shift is a valuable tool. It allows you to over-ride exposure when in Aperture or Shutter Speed priority modes. Why would you need that? What if you’re in a situation where the light changes quickly – or as in my case, where the subject moves from a dark to light or light to dark area quickly? How do you compensate quickly? The answer is Safety Shift.
With Safety Shift on, the camera will adjust either your shutter speed or aperture (depending on whether youre in Av or Tv mode) to make sure you get the best exposure. If, however, you are using a particular shutter speed or aperture to achieve a specific look to your images, the EOS 5D Mark III, EOS-1D X, EOS-1D Mark IV and EOS-1D Mark III DSLRs offer the ability to adjust the exposure using ISO instead. (Auto ISO) This allows you to retain control of your shutter speed or aperture and thereby maintain the look you were after, using the extensive ISO ranges of the cameras to get the correct exposure. (Auto ISO works the same way on some of the higher-end and newer Nikon cameras.)
If none of this is making sense, you need to do two things.
1) Learn the – Aperture, Shutter Speed, ISO – these three tools work to deliver the correct exposure. They work in concert with each other. You need to understand this if you ever want to shoot in manual mode.
2) Read the camera manual. All of this is very well explained in every camera manual I’ve ever seen, yet most studies show that less than 15% of people read the manual.
If you’re a Canon user, read the section of your manual dealing with Safety Shift and practice using it. If you’re a Nikon user read about Auto ISO. Even if you think you’ll NEVER ever use it – learn it. The more you know about your camera, the better your chances of being ready when you see the next great shot.