Learn How to Focus A Camera Lens from Our Optical Engineering Consultants.
Getting Started With Your Camera Lens Focus Process
1.) Find your Camera Focus Card
We include a focus card with the majority of our M12 Lenses and CS Mount Lenses. We suggest a minimum of 4 cards for the proper focus process.
The 2" FocusCard 36 has 36 square wave spoke line pairs and a contrast ratio of 80:1. This is a subjective focus tool and is not suitable for objective eSFR measurements.
2.) Calculate the FoV of Your Lens. Then, find the FoV that corresponds to 50% from the center to the DFoV.
3.) Determine the Nominal Object Distance for your Camera
Consider all of the objects you intend to capture with your vision system.
What is the closest? What is the furthest? What is the median of the object distances?
A good starting point is to set the focus target(s) at the median object distance.
Our Depth of Field Calculator can also provide the hyperfocal distance of the sensor+lens combination. This is the maximum distance the FocusCard should be set.
4.) Prepare Your Camera Set Up
Set 1 focusing card in each diagonal direction 50% from the center to the corners. Use the values calculated in step #2. These should be set at the closer of the Nominal Object Distance, or the Hyperfocal distance, calculated in step #3.
You can move these around, but using only a single target in the center usually does not yield optimal focus across the image.
We recommend using a neutral gray background to minimize auto-exposure clipping.
5.) Start Your Camera. Go Past Focus. Come Back.
1.) Open a real-time output stream from the camera. Refer to your camera manufacturer for details.
2.) Clean your sensor, lens threads, lens mount threads, and lens rear surface using an air dust tool. Don't use an aerosol-type air dust tool; it needs to only use room air.
3.) Slowly thread your lens into focus.
4.) Go approximately a 1/4 to 1/2 of a turn past focus. You want to be able to clearly determine that the camera is out of focus.
5.) After the lens starts going out of focus, return to best focus using 1/16 turn increments.
This process makes sure you are at the true peak contrast.
6.) Lock Focus and Return to Console
Use a low-outgassing adhesive to secure focus. If you do not have adhesive, you can use a focus lock ring. We do not recommend using a set screw as your camera can go out of focus on one side.
Return to console to start using computer vision. Let us know if you have any feedback or questions about these instructions.