Target Grid | Why You Need a High Precision Calibration Target
Calibration Target Printing

Circle Targets

486 Reviews

We now offer Circle targets on Dibond with an Anti-Reflective surface "flood white" print option for a true matte finish, making them more easily detected in your computer vision pipeline. Read More

  • 0.125
  • 1/2" All Corners $3.00
  • 1/4" All Corners $3.00
  • 3/8" All Corners $3.00
  • Special $54.59


Camera Calibration With OpenCV | Chessboard or Asymmetrical Circle Patterns

This short video will show you how to use Chessboard and Asymmetrical circle pattern grids with OpenCV. Press play to skip the chessboard pattern testing and jump ahead to view Asymmetrical Circle Grid.

Circle Targets

If put to a quality test, our calibration targets are sure to come on top, thanks to their impeccable construction. Our circle targets are crafted from ⅛” rigid Dibond, ensuring each target has just the correct specifications to withstand indoor and outdoor usage.

With our quality products, you can take your project goals to the next level thanks to the high precision nature of our calibration targets. Not only are they ultra-stiff and flat, but they are also lightweight to ensure you make the most out of your calibration applications.

Given the competitive thermal and rigidity targets, expect to enjoy a quality performance.

All target patterns undergo a flood white edge-to-edge print process, giving them an authentic matte finish. If you are looking for items suitable for high-accuracy machine vision applications needing impeccable optical performance plus compatible physical capabilities, our products will have you covered.

Dibond Features

Dibond signage has forever been an industry standard for indoor and outdoor business signs. The material is water, weather, warp resistant and rust proof. It's ultra flat and rigid structure makes Dibond the perfect material for calibration targets.

  • Light weight
  • Ultra flat surface
  • Anti-reflective surface (flood white finish) pitch black on pure white
  • Rigid and sturdy
  • Water, weather & rust proof

Technical Specifications

  • Material Thickness: .125"
  • Panel Type: Aluminium Composite Panel
  • Temperature Range: from -50°C to +80°C
  • Fire Classification: CLASS P/0/1
  • Physical Weight: 0.78125 lbs per ft.²

Common Circle Grid Target Sizes

Helpful Ordering Tips

  1. Order the exact sizes that match your file's artboards; use the keyboard to add decimals if needed.
  2. Upload your own custom files, vector PDF files are preferred for optimal print results.
  3. Full-scale files are required to avoid the files being scaled up or down to fit the image on the board's order size. Need a PDF for print? Try our Free Online Calibration Pattern Generator free now!
  4. During the proofing process, always double-check and compare the file size to each board order size ( is not responsible for artwork scaling if the incorrect board sizes are ordered and proofs are approved incorrectly).
  5. If you have questions about the artwork uploaded to an order; please call, email, or start a live chat before sending the art files to print. Production will begin within 10 mins of approval of artwork. Once production begins, we can not remove approved art files from the production line.

What to Expect from Our Target Grid Patterns

We present quality calibration target grids geared to offer you precise localization of saddle points. The orientations used ensure the robust indexation on partly visible target grids and multifaceted objects. These quality grid patterns ensure superior edge detection to ensure your camera calibration processes are always perfect.

What Are Your Recommendations for Choosing a Target Grid?

Accurate camera calibration is crucial to ensure image precision much-needed in computer vision tasks and many machine types. As you go about picking a suitable target grid for your application, here are some of the best practices to keep in mind.

After extensive experimentation combined with theoretical considerations, we can confidently recommend these considerations to any photographer looking for high image accuracy.

Target Grid Size Selection

Picking a suitable calibration target grid size is of prime importance. Your target grid needs to be a size capable of constraining parameters adequately.

Targets should occupy half of your total area as viewed fronto-parallel in a camera image.

Feature Count

Ensure your target grid has a dense feature count. Fine grid patterns are excellent for camera calibration. However, using targets with very fine patterns may be challenging to detect.

To enjoy the best camera calibration results, use fine target grid patterns on 3MPx cameras and above. Also, ensure your lighting is superb and in check for easy calibration.

Target Flexibility

Why not try out uniquely coded targets like CharuCo patterns? The CharuCo grid allows you to capture observations at the center and up to your camera lens and sensor's extreme periphery. Therefore, you can adequately obtain distortion parameters.

What's more, such a target allows you to get data even when some feature points fail to achieve the other requirements.

How Do I Properly Use a Target Pattern?

While you may select a durable and good target, you may still fail to obtain the performance you expect from your grid. With the vast experience we have in calibration, coming across numerous mistakes when using grid patterns is one of our enjoyed advantages.

Let's help you tune up your camera calibration process and avoid common target usage mistakes.

Optimal Calibration Distance

Calibrate your camera at roughly the working distance of your last application. Focus your camera at this particular distance, and don't change your lens focus once you finish calibration.

Quantity and Coverage Extent

Capture the target grid images from multiple tilts and locations. Adjust the target pattern's position to ensure total coverage of your image area.

You can properly determine lens distortion using fronto-parallel photos. However, the estimation of your focal length depends on studying foreshortening.

Take both fronto-parallel pictures and images of your target in both vertically tilted and horizontally tilted positions of up to 45 degrees from the baseline. Tilting past 45 degrees is unwise as it negatively impacts the accuracy of feature localization, and it may lead to biased camera calibration.

Have Good Lighting

While many photographers tend to overlook lighting while calibrating their cameras, adequate lighting is a factor impacting calibration accuracy.

Illuminate your calibration target with controlled lighting and in a diffuse manner. Strong point light sources result in uneven illumination. This can cause the failure of detecting some points while also limiting the utilization of the dynamic range of your camera.

Improper lighting is not only about point sources, as shadows can have a similar limiting effect.

Ideal Number of Target Observations

Ample target observations are necessary for proper calibration. Typically, you need a minimum of six target images for fairly accurate calibration. If you are using a distortion model or have a higher-order camera, taking more pictures of the target will ensure a better calibration result.

Grid Pattern and Camera Placement

Accurate camera calibration also requires a proper camera and target mounting. Mount your camera and grid pattern while lying horizontally on firm support or vertically. This way, you can minimize the amount of bow and distortion in large targets.

Another placement tip is to consider adjusting your camera position instead of your target grid. Try not to touch your camera while you take the grid pattern photos. Moreover, ensure you use legit tripod support.

Bad Observation Elimination and Error Analysis

Carefully study your reprojection errors for both per-feature and per-view incidences. If any reprojection error seems like an outlier, remove it and repeat the calibration process.

Take time looking at each reprojection error. What is the error magnitude and direction? What is their relation with the position? Ideally, the position should not correlate to the former two but instead, point haphazardly in undefined directions.

With good software, you can get powerful visualizations for proper reprojected error investigation and analysis.

Achieving Impeccable Camera Calibration

Getting low reproduction errors does not automatically define a superb camera calibration. A low error is a mere indication that you can describe the model you used with the available evidence/ data.

The failure to obtain camera calibration accuracy even with low reproduction errors can result from overfitting. Parameter uncertainties point to the extent of constraining the used camera model.

Finally, know that calibration accuracy primarily depends on the calibration target grid used. Inkjet and laser printed targets are only ideal for testing and result validation.

Our quality grid patterns available in various sizes, and both coarse and fine options ensure you calibrate your camera with ease.

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Frequently asked Questions


What are calibration targets?

Circle calibration targets are small, round discs with a single black dot in the center. They are used to calibrate cameras and other optical instruments.

The target is placed on a flat surface at an appropriate distance from the instrument's lens so that it fills most of the frame when looking through the viewfinder or eyepiece. The camera will then be focused on this point, ensuring objects at different distances appear equally sharp in photographs taken by that camera.

Is a calibration target the same as a calibration pattern?

Calibration targets are used in calibration, which is the process of matching a measurement device to a known standard. Calibration targets can be printed on paper or displayed on a computer screen. They may be used with any measuring instrument, including optical devices such as microscopes and cameras.

What is a calibration grid?

A calibration grid is a set of lines that can be used to measure the accuracy of an instrument. A calibration grid is usually made up of parallel lines spacing between them and some scale. The scale may be in centimeters, inches, or any other unit, depending on what measurement system you are using.

How is camera calibration done?

Camera calibration is the process of estimating how a camera responds to light and producing an internal map or matrix that relates the relative distances between objects in the 3-D scene to their image positions.

Camera calibration can be done using two methods: photogrammetry or geometric modeling. Photogrammetry utilizes photographs taken by a camera to create a three-dimensional model of an object. At the same time, geometric modeling relies on measurements from other sources such as CAD drawings or laser scanning.

How accurate is a calibration target in calibrating an instrument?

A calibration target can be considered as the best-known method to calibrate instruments. The calibration target usually is very accurate. Several factors are involved in achieving a correct result when using the calibration target to calibrate an instrument.

The calibration target is designed to be used in a specific environment, and each condition is considered in the design of the target. The calibration target is a flat, concave piece of glass or similar medium. The surface of the target has a predetermined contrast.

An instrument that is to be calibrated may have a predetermined contrast. This can ether be arranged on the face of the instrument, or the object's outer surface can be designed so that it has a known contrast.


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