Adjusting The Back Focus of a Lens

In most cases, changing a lens will not require adjusting the back focus of a lens. But when a lens does not hold focus at both ends of the zoom range, you may need to adjust the back focus. By adjusting the back focus, you are changing the distance of between the pick-up device and the rear element of the lens. Technically, it’s the distance from the vertex of the rearmost element of the lens to the focal plane, but we’ll keep it simple. Note that not all lenses have a back focus adjustment.


The Steps

Before starting, put the camera on a tripod and adjust your camera’s viewfinder so it is in sharp focus. Ideally, you’d want a test pattern chart (looks like a dart board) to be at least 75 feet from the camera. Otherwise, as far as possible. If you don’t have a test chart, Use a page from a magazine.

  1. Set the iris to manual.
  2. Set the zoom to manual.
  3. Open the iris to 1.4 or its widest aperture. If the illumination on the test chart is too bright for the open iris, reduce the light or move the chart to a darker area.
  4. Turn the zoom barrel to extreme telephoto.
  5. Focus on the chart.
  6. Set the zoom to wide angle.
  7. Loosen the back focus ring retaining knob.
  8. Adjust the back focus ring for the sharpest focus.
  9. Repeat steps 4 through 8 until focus is consistently sharp.
  10. When it is, tighten the back focus ring retaining knob to secure the ring.

Note: Most lenses are at their sharpest focus at about a middle iris position like F5.6.


Keep Reading...

Google and GoPro Make 16 Cam VR Rig

Wanted: Filmmakers To Test Google’s GoPro VR Camera Rig

GoPro and Google have joined forces to create a Virtual Reality camera rig with 16 GoPro HERO4 cameras. It’s called Jump. It can transform 16 pieces of video into one stereoscopic 360 degree VR video. The 360 degree camera array allows all 16 cameras to act as one. This makes camera syncing easy, and includes […]

Read More
Produce Business Videos

Professional Video Producer: How To Start a Successful Video Production Business

Start part-time or full-time in this lucrative and satisfying work. Earn the respect of small businesses, corporations and non-profits who rely on your expertise. This is an amazing adventure and the best way to pay for video equipment!

Read More
Vine Video

Making Money Producing Videos For Vine

Producing Vine videos for money.

Read More
C'est Un rendezvous

Ford Motors remakes “C’était un rendez-vous”

The famous French film of high speed (illegal) driving through the streets of Paris is being remade by Ford Motors and this one will be a 360 degree video.

Read More


Facebook Comments

Leave a Reply

Your email address will not be published. Required fields are marked *


  • Forbes Magazine calls VideoUniversity one of the best business-to-business sites for digital video production.
  • WINNER
    Videography Magazine's
    "Website of the Month" Award
  • WINNER
    PC Magazine Online "Best Desktop Video Site" Award
  • WINNER
    CyberFilm School's "FOUR STAR" Award