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.
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.
- Set the iris to manual.
- Set the zoom to manual.
- 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.
- Turn the zoom barrel to extreme telephoto.
- Focus on the chart.
- Set the zoom to wide angle.
- Loosen the back focus ring retaining knob.
- Adjust the back focus ring for the sharpest focus.
- Repeat steps 4 through 8 until focus is consistently sharp.
- 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.
Every day some 8 Billion videos are viewed on Facebook, but most of them are viewed silently. As you probably know, video on Facebook plays automatically, but the sound is off by default. And most people really do not want to turn the sound on. So if you’re trying to promote anything with a video […]Read More
Full HD 360-Degree Spherical Panoramic Digital Camera Here’s what my friend Tim Doherty shot with his Ricoh Theta S. Use your mouse to click and slide the view. The Ricoh Theta S is available on Amazon. The Theta S will shoot 1080p HD at 30fps for up to 25 minutes per charge. It can also […]Read More
How to double your video video views by breaking the fourth wall.Read More
Lufthansa and DJI Drone Technology Lufthansa Aerial Services, a division of Lufthansa Consulting, today signed a deal with DJI to use the world’s leading drone-maker’s aerial platforms to develop commercial applications for its key customers. A recent pilot project to inspect rotor blades on wind turbines was just completed by the Lufthansa and DJI. Other […]Read More