Refresh your focus with lens calibration.

What is lens calibration?

Lens calibration, also known as autofocus calibration, is a method of fine-tuning where the focus point falls in your image when you are autofocusing. Theoretically, autofocus should always produce sharp images, with your chosen subject in focus. However, in a DSLR camera, an autofocused image requires clear communication between the lens (which lets in the light), the camera’s autofocus chip (which determines when the image is in focus) and the camera’s sensor (which creates the image).

This leaves room for images to appear in focus in the viewfinder, only to be out of focus when they’re actually produced. And it can happen at any focal length.

“That’s the worst thing,” says photographer Felipe Silva. “Say you’re shooting a client’s wedding, you use autofocus and your image is focused on the back of their ear instead of their eye. Your camera can tell you that it’s focused, but when you zoom in really close, you can see that it’s a little bit off.”

“It’s like a miscommunication between camera and lens,” says photographer Jason Weingart. “And lens calibration corrects how ‘off’ the lens is.”

What causes this unexpected blur?

When you first buy a lens, it should function predictably with your camera body and your autofocus system should work well. However, even new cameras and lenses may have some slight margins of error in how their components are positioned. Over time, inner components can shift and cause your photos to be slightly blurry.

How often should you calibrate your lenses?

You need to calibrate only if and when you notice that your camera’s autofocus isn’t producing a clear photo with a certain lens. It can depend on how much wear your equipment gets. But for some, this may occur about every six months to two years for each camera and lens combination.

If you change lenses often, don’t worry. Many cameras recognise the specific serial number assigned to a lens and will remember its calibration setting from the last time you set it.

Do you need to calibrate a mirrorless camera?

No, lens calibration is not needed with a mirrorless camera and lens. This is because mirrorless cameras do not use an autofocus chip. Instead, the camera’s sensor does both the focusing and the imaging, so there is no room for miscommunication.

How to calibrate your lens.

The calibration process involves taking a series of photos in a controlled way, so you can see exactly how your focus is off. You can then correct it using your camera settings. If the intended subject of your image is blurry, that means your camera is either back focusing or front focusing. A back focus is when the focus falls slightly behind your subject and a front focus is when the focus falls slightly in front of it.

When you calibrate, you’re telling your camera to shift the focus one way or the other when it does the imaging, so your final photo matches what you see in the viewfinder or screen when you take it.

Lens calibration tools and set-up.

To calibrate, you need a well-lit environment, a tripod, a flat surface and a subject to photograph that has easily measurable markings. You can purchase special objects to use as the subject of your test photos, which have been specifically designed to help you to find your focus, such as focus pyramids or calibration charts. Or you can create your own prop.

One method is to use a hardcover book and a 12-inch ruler with clear markings. Stand the book up on its bottom edge, so the cover is facing the camera. Tape a small piece of paper with an “X” drawn on it to the front cover at the centre line. Then balance the ruler against an object, like a coffee mug, so it’s at a 30-degree angle. You want the ruler placed right beside the book, with the top end tilting away from the camera and the middle 6-inch point lining up against the centre of the book cover where you’ve taped the paper.