P#13 Q4B: What are Mirror Lockup and Back Focus and How Do They Apply to Landscape Photography?

Mirror Lockup and Back Focus 101

Jennifer Wu: Mirror lockup is used to make an image sharper. When we take a photograph, the mirror in the camera goes up and it creates a vibration. This makes our image appear not quite as sharp.

With landscape photography, we can use a tripod to help keep our images sharp, and we can also use a technique called mirror lockup.

When taking our landscape photographs, we can set the camera to do what's called mirror lockup. This brings the mirror up, and then waits a second or two before it takes the photograph. This eliminates the vibration so we don't have any loss of sharpness.

Whenever I'm using a long lens or have a long exposure, I use mirror lockup. This ensures a sharp image.

All DSL cameras will be able to do that. Look in your camera's owner's manual for instructions on how to set your camera to use the mirror lockup feature.

Audri Lanford: What about back focus?

Jennifer Wu: The back focusing button is referred to by different names. What it does is, instead of using the shutter button to focus and create the exposure, it allows you to have the focusing set by a button on the back of the camera, so that the shutter button just controls taking the picture.

That's really helpful because a lot of times when you're photographing landscapes, our subject isn't necessarily in the center of the frame. We might want our subject off center or in the foreground, or some area like that. If I want to focus on that, I can use the back button I've set to autofocus. I just focus on my subject and then I can just use the shutter for taking the photograph.

When I do this, the shot is already focused so when I press the shutter button it's not going to change the focus. It's going to have the focus in the right area. I won't have to hold it halfway and recompose.

Audri Lanford: Roy Toft talked about this as well, but didn't use the term back button. (You can read more about how Roy describes autofocus here.)

To Conclude

While your tripod definitely plays an important role in keeping your landscape images sharp, there are other tools and techniques at your disposal. Thanks to Jennifer Wu, you now know that mirror lockup and back focus are two of them.