# \#practical **URL:** https://forum.opencv.org/tag/practical/233.md [Latest](https://forum.opencv.org/latest.md) · [Categories](https://forum.opencv.org/categories.md) · [Tags](https://forum.opencv.org/tags.md) --- ## [Your opinion about industrial usb cam](https://forum.opencv.org/t/your-opinion-about-industrial-usb-cam/3592)
**Author:** [@delcencen](https://forum.opencv.org/u/delcencen)\ **Replies:** 1\ **Last updated:** [May 31, 2021, 8:45am UTC](https://forum.opencv.org/t/your-opinion-about-industrial-usb-cam/3592 "2021-05-31T08:45:35Z")
I now my question is not directly in link with opencv .For the moment i use old webcam with different integrated fonction(zom x 10,light correction…) and sometime those diffrence make problems. So i wonder if i don’t av… --- ## [Commercial vs printed calibration boards](https://forum.opencv.org/t/commercial-vs-printed-calibration-boards/16655)
**Author:** [@thisischris](https://forum.opencv.org/u/thisischris)\ **Replies:** 0\ **Last updated:** [March 1, 2024, 3:53pm UTC](https://forum.opencv.org/t/commercial-vs-printed-calibration-boards/16655 "2024-03-01T15:53:15Z")
Hello, I’m trying to calibrate a multi-camera setup for research. Is there a significant difference between using commercial calibration patterns (like Calib.io) or hand-made patterns (printed at home or at a print shop… --- ## [Hand-eye Calibration](https://forum.opencv.org/t/hand-eye-calibration/1880)
**Author:** [@Anders](https://forum.opencv.org/u/Anders)\ **Replies:** 35\ **Last updated:** [February 5, 2024, 12:14pm UTC](https://forum.opencv.org/t/hand-eye-calibration/1880 "2024-02-05T12:14:39Z")
Hello, I am trying to do Hand eye calibration with the new OpenCV functions provided in the 4.1 version. I currently have a camera/lidar (Intel realsense L515) mounted to the end effector/flange of an UR5-e 6DOF robot m… --- ## [Using OpenCV to detect unpolished area of metalic element](https://forum.opencv.org/t/using-opencv-to-detect-unpolished-area-of-metalic-element/13759)
**Author:** [@Dewo21](https://forum.opencv.org/u/Dewo21)\ **Replies:** 5\ **Last updated:** [July 5, 2023, 3:53pm UTC](https://forum.opencv.org/t/using-opencv-to-detect-unpolished-area-of-metalic-element/13759 "2023-07-05T15:53:55Z")
Hi guys, I’ve got recently an interesting project to do. I’m trying to get the unpolished area of pilers (not sure if it’s right word, looks like a scissors). The problem is that this certain area is barely visible by h… --- ## [Inexpensive USB cameras with large sensors (9mm or longer diagonal) that work well with opencv](https://forum.opencv.org/t/inexpensive-usb-cameras-with-large-sensors-9mm-or-longer-diagonal-that-work-well-with-opencv/11749)
**Author:** [@BruceAllen](https://forum.opencv.org/u/BruceAllen)\ **Replies:** 4\ **Last updated:** [January 25, 2023, 8:59pm UTC](https://forum.opencv.org/t/inexpensive-usb-cameras-with-large-sensors-9mm-or-longer-diagonal-that-work-well-with-opencv/11749 "2023-01-25T20:59:18Z")
I want to install a USB camera at the focal plane of an instrument. This means putting the raw sensor at that location, so no lens or other focussing system is needed. The image on the focal plane is a 12mm diameter ci… --- ## [Road map to solve recognition problem](https://forum.opencv.org/t/road-map-to-solve-recognition-problem/7786)
**Author:** [@mateczek](https://forum.opencv.org/u/mateczek)\ **Replies:** 4\ **Last updated:** [March 6, 2022, 7:58am UTC](https://forum.opencv.org/t/road-map-to-solve-recognition-problem/7786 "2022-03-06T07:58:54Z")
I’m maintenance department worker (electric + automation) on my factory is some application which recognition wheel (model from small active element list, and measure angle). I want try wrote similar application and tea… --- ## [How to get clear images from webcam in movement with Python?](https://forum.opencv.org/t/how-to-get-clear-images-from-webcam-in-movement-with-python/7458)
**Author:** [@willsm](https://forum.opencv.org/u/willsm)\ **Replies:** 3\ **Last updated:** [February 7, 2022, 2:46pm UTC](https://forum.opencv.org/t/how-to-get-clear-images-from-webcam-in-movement-with-python/7458 "2022-02-07T14:46:33Z")
Hey guys! Is it possible to get very sharp images from a webcam capture? When the objects I want to detect in the image are stopped, the sharpness is excellent, but when the objects are in motion, the frames captured b… --- ## [Label detection advise needed](https://forum.opencv.org/t/label-detection-advise-needed/5719)
**Author:** [@wency.www](https://forum.opencv.org/u/wency.www)\ **Replies:** 28\ **Last updated:** [December 25, 2021, 11:50am UTC](https://forum.opencv.org/t/label-detection-advise-needed/5719 "2021-12-25T11:50:45Z")
Hi, guys! I would like to see your suggestion about this: I’m working on an application that recognizes labels on postal items. Attached below are two sample files. One of them has a white label on a relatively dark b… --- ## [Correct image for distortion by external lens](https://forum.opencv.org/t/correct-image-for-distortion-by-external-lens/5301)
**Author:** [@Oryx](https://forum.opencv.org/u/Oryx)\ **Replies:** 2\ **Last updated:** [September 26, 2021, 4:24am UTC](https://forum.opencv.org/t/correct-image-for-distortion-by-external-lens/5301 "2021-09-26T04:24:02Z")
Hi All I am capturing images of an object inside an acrylic cylinder filled with oil (simple plan view sketch below). Due to the refractive index mismatch the cylinder acts as a lens and distorts my images horizontally… --- ## [Feasability and suggested approach to detect river-waterlevels?](https://forum.opencv.org/t/feasability-and-suggested-approach-to-detect-river-waterlevels/4418)
**Author:** [@sirtet](https://forum.opencv.org/u/sirtet)\ **Replies:** 7\ **Last updated:** [July 22, 2021, 5:59pm UTC](https://forum.opencv.org/t/feasability-and-suggested-approach-to-detect-river-waterlevels/4418 "2021-07-22T17:59:06Z")
Hi everyone. I am new to CV (or, actually not even started yet), so assume no specific knowledge on my side… I want to read waterlevels from pictures like these here: https://data.rivermap.org/wassenphoto/hs-index2.ph… --- ## [Using the optical flow for motion detection in Supernova remnants in astronomy](https://forum.opencv.org/t/using-the-optical-flow-for-motion-detection-in-supernova-remnants-in-astronomy/4236)
**Author:** [@Aktro](https://forum.opencv.org/u/Aktro)\ **Replies:** 1\ **Last updated:** [July 8, 2021, 4:37pm UTC](https://forum.opencv.org/t/using-the-optical-flow-for-motion-detection-in-supernova-remnants-in-astronomy/4236 "2021-07-08T16:37:15Z")
Hi, This topic is about a recent experimentation I’ve tried on using the openCV optical flow implementation to measure the velocity and expansion of the blast wave in an exploded star (known as supernova remnant) using … --- ## [How to evaluate camera calibration quality?](https://forum.opencv.org/t/how-to-evaluate-camera-calibration-quality/4135)
**Author:** [@Witek](https://forum.opencv.org/u/Witek)\ **Replies:** 5\ **Last updated:** [July 3, 2021, 5:38pm UTC](https://forum.opencv.org/t/how-to-evaluate-camera-calibration-quality/4135 "2021-07-03T17:38:21Z")
Hi, I am wondering how I can evaluate the quality of camera calibration. The average reprojection error is SOME way, but it depends on the calibration target distance and its placement in the image, so it cannot be used… --- ## [Using opencv to track change over time](https://forum.opencv.org/t/using-opencv-to-track-change-over-time/3991)
**Author:** [@LemonSplat](https://forum.opencv.org/u/LemonSplat)\ **Replies:** 3\ **Last updated:** [June 24, 2021, 5:29am UTC](https://forum.opencv.org/t/using-opencv-to-track-change-over-time/3991 "2021-06-24T05:29:13Z")
So I am trying to write a program to see the change in two images over time (images are attached bellow) I want the program to see change in color and shape. The two images change some color and some parts of the pipe ar… --- ## [CUDA Fast detector much slower than normal FAST](https://forum.opencv.org/t/cuda-fast-detector-much-slower-than-normal-fast/3532)
**Author:** [@Kansai](https://forum.opencv.org/u/Kansai)\ **Replies:** 9\ **Last updated:** [May 28, 2021, 9:08am UTC](https://forum.opencv.org/t/cuda-fast-detector-much-slower-than-normal-fast/3532 "2021-05-28T09:08:31Z")
I am using OpenCV FAST Feature detector in both CPU and CUDA versions as follows: For the normal CPU version cv::FAST(img,kps, threshold, true); For the CUDA version ptrDetector= cv::cuda::FastFeatureDetector::create… --- ## [Making a checkerboard for UV Camera Calibration](https://forum.opencv.org/t/making-a-checkerboard-for-uv-camera-calibration/3450)
**Author:** [@BradenLuan](https://forum.opencv.org/u/BradenLuan)\ **Replies:** 1\ **Last updated:** [May 20, 2021, 8:06pm UTC](https://forum.opencv.org/t/making-a-checkerboard-for-uv-camera-calibration/3450 "2021-05-20T20:06:47Z")
I’m currently trying to perform camera calibration on a camera lens with a UV filter on it using the checkerboard method. I’ve had a very tough time making the checkerboard visible with enough contrast for the FindChessb… --- ## [Using Open CV to detect greenhouse crop detection & infestation](https://forum.opencv.org/t/using-open-cv-to-detect-greenhouse-crop-detection-infestation/2365)
**Author:** [@jeffingeorge](https://forum.opencv.org/u/jeffingeorge)\ **Replies:** 70\ **Last updated:** [May 20, 2021, 6:46am UTC](https://forum.opencv.org/t/using-open-cv-to-detect-greenhouse-crop-detection-infestation/2365 "2021-05-20T06:46:15Z")
Hey, Jeffin here, I’m new to Open CV. am building hardware system to detect greenhouse crop infestation using the help of Open CV. I tried some cascade and did some training the results are zero. What all the things i n… --- ## [How to Follow the Action on a Basketball Court](https://forum.opencv.org/t/how-to-follow-the-action-on-a-basketball-court/3180)
**Author:** [@tps](https://forum.opencv.org/u/tps)\ **Replies:** 6\ **Last updated:** [May 12, 2021, 2:20pm UTC](https://forum.opencv.org/t/how-to-follow-the-action-on-a-basketball-court/3180 "2021-05-12T14:20:13Z")
Hi All Is it possible? I want to track players ( and the basketball if possible ) on a basketball court and decide where the action is. Tracking input video comes from a stationary wide angel camera that covers the en… --- ## [How to remove reflections when wearing glasses in order to detect the eye directions correctly](https://forum.opencv.org/t/how-to-remove-reflections-when-wearing-glasses-in-order-to-detect-the-eye-directions-correctly/2987)
**Author:** [@Daniel\_Adama](https://forum.opencv.org/u/Daniel_Adama)\ **Replies:** 3\ **Last updated:** [April 27, 2021, 7:15am UTC](https://forum.opencv.org/t/how-to-remove-reflections-when-wearing-glasses-in-order-to-detect-the-eye-directions-correctly/2987 "2021-04-27T07:15:32Z")
Can anyone help, I am working on an eye detection project, to detect the directions of the pupil, say left or right, it works well but whenever I use glasses it glitches, it starts to detect the pupil directions wrongly… … --- ## [Custom Object detection - training my own detector but cannot get training tool to work](https://forum.opencv.org/t/custom-object-detection-training-my-own-detector-but-cannot-get-training-tool-to-work/2924)
**Author:** [@CaptainPineapple](https://forum.opencv.org/u/CaptainPineapple)\ **Replies:** 7\ **Last updated:** [April 22, 2021, 9:22pm UTC](https://forum.opencv.org/t/custom-object-detection-training-my-own-detector-but-cannot-get-training-tool-to-work/2924 "2021-04-22T21:22:29Z")
Hello there, for a project i need to enable my programm to detect a given object in an image to extract object position and the objects bounds. Since we already use opencv for the image processing we do, the idea wa… --- ## [Object location in a busy picture (bin picking)](https://forum.opencv.org/t/object-location-in-a-busy-picture-bin-picking/2897)
**Author:** [@Selage](https://forum.opencv.org/u/Selage)\ **Replies:** 3\ **Last updated:** [April 21, 2021, 6:09pm UTC](https://forum.opencv.org/t/object-location-in-a-busy-picture-bin-picking/2897 "2021-04-21T18:09:23Z")
Hi all, I’m i need off some advise. I’m studying the possibility to locate know objects (XY) in a picture. You can call it bin picking, but then again (done with a lasergrid) it is not accurate enough, because of the … --- ## [How to find a generic straw segmentation method?](https://forum.opencv.org/t/how-to-find-a-generic-straw-segmentation-method/2215)
**Author:** [@zgle](https://forum.opencv.org/u/zgle)\ **Replies:** 8\ **Last updated:** [March 19, 2021, 1:16pm UTC](https://forum.opencv.org/t/how-to-find-a-generic-straw-segmentation-method/2215 "2021-03-19T13:16:22Z")
I am working on a project to find all straws in the images. My thought is to use the Thresholding, Morphology, and ConnectedComponents to get the contours, see the following code and attached figures. It is easy to try s… --- ## [How to detect film area?](https://forum.opencv.org/t/how-to-detect-film-area/2063)
**Author:** [@KoreaKim](https://forum.opencv.org/u/KoreaKim)\ **Replies:** 9\ **Last updated:** [March 16, 2021, 9:43am UTC](https://forum.opencv.org/t/how-to-detect-film-area/2063 "2021-03-16T09:43:44Z")
I want to check the presence or absence of a film There is a film on the top of the center border How can I detect it? Thank you in advance. --- ## [How to count number of passengers in a vehicle?](https://forum.opencv.org/t/how-to-count-number-of-passengers-in-a-vehicle/1817)
**Author:** [@blue\_joe](https://forum.opencv.org/u/blue_joe)\ **Replies:** 2\ **Last updated:** [March 7, 2021, 5:00am UTC](https://forum.opencv.org/t/how-to-count-number-of-passengers-in-a-vehicle/1817 "2021-03-07T05:00:17Z")
Hi, I’m currently planning planning to take a video of a highway from an overhead bridge and be able to count the number of passenger in each vehicle through a bounding box and here is where I’m stuck at. Sample Image f… --- ## [solvePnP's translation coordinates are from camera's lens or from the sensor?](https://forum.opencv.org/t/solvepnps-translation-coordinates-are-from-cameras-lens-or-from-the-sensor/1773)
**Author:** [@ThiroSmash](https://forum.opencv.org/u/ThiroSmash)\ **Replies:** 6\ **Last updated:** [February 24, 2021, 10:45pm UTC](https://forum.opencv.org/t/solvepnps-translation-coordinates-are-from-cameras-lens-or-from-the-sensor/1773 "2021-02-24T22:45:23Z")
Title. I’m getting the camera coordinates relative to a 2D marker positioned at (0,0,0). I’m trying to see how precise it is, so I’m only measuring the depth (Z coordinate), aligning the other two axis, and I’ve noticed… --- ## [Coordinates of touching the image projected from behind. (touchwall)](https://forum.opencv.org/t/coordinates-of-touching-the-image-projected-from-behind-touchwall/1584)
**Author:** [@Laszlo\_Ivak](https://forum.opencv.org/u/Laszlo_Ivak)\ **Replies:** 8\ **Last updated:** [February 17, 2021, 9:17am UTC](https://forum.opencv.org/t/coordinates-of-touching-the-image-projected-from-behind-touchwall/1584 "2021-02-17T09:17:52Z")
As a rookie, I greet everyone on the forum! Help me please! I would like advice on how I could implement openCV: Rear projected optical image on a 2m x 2m transparent screen. person touches the canvas with his hand 2 … --- ## [Tracking skin markers](https://forum.opencv.org/t/tracking-skin-markers/1548)
**Author:** [@Elad](https://forum.opencv.org/u/Elad)\ **Replies:** 2\ **Last updated:** [February 15, 2021, 5:02am UTC](https://forum.opencv.org/t/tracking-skin-markers/1548 "2021-02-15T05:02:18Z")
Hi there, I’m working on a project where I need to label key points on the body (for example knuckles). I’m free to paint anything on the body. Computation time is not a factor. I originally tried to draw dots in diff…