Captured Image in OpenCV is unsharp

Question

First my Setup: Windows 10, Asus Notebook, Logitech C920 HD Pro Webcam, Opencv-Python 3.4.4.19

When I manually take a photo with the webcam using the Windows 10 Camera App, it is sharp. But if I program a code in Python and use OpenCV the taken photo is blurred (unsharp). When I press the space bar, a photo is taken.

I already tried to play with the contrast, brightness and FPS. Unfortunately this didn't lead to any result.

import cv2
import os
cam = cv2.VideoCapture(1)
cv2.namedWindow("test")
cam.set(3, 1920)
cam.set(4, 1080)
img_counter = 0
myfile="XXX"
if os.path.isfile(myfile):
    os.remove(myfile)
else:    
    print("Error: %s file not found" % myfile)
while True:
    ret, frame = cam.read()
    cv2.imshow("test", frame)
    if not ret:
        break
k = cv2.waitKey(1)
if k%256 == 27:
    print("Escape hit, closing...")
    break
elif k%256 == 32:
    img_name = "Bild{}.png".format(img_counter)
    cv2.imwrite(img_name, frame)
    print("{} written!".format(img_name))
    img_counter += 1
cam.release()
cv2.destroyAllWindows()

Are there settings for OpenCv to get the image sharper? In the final stage I have 3 cameras which automatically take a photo one after the other.

Unsharp Image (OpenCV)
Sharp Image (Windows 10 Kamera App)
Image cv2.imshow

Can you please post some pictures? Examples would really help — Guilherme Vogt, Feb 13 '19 at 16:47
Shouldn't the section from `k = cv2.waitKey(1)` and before `cam.release()` be indented right? Also, avoid setting the frame width and height in `cam.set()` and upload the raw image from the camera. It's possible that resizing is causing the blur — Shawn Mathew, Feb 13 '19 at 19:20
@MarkSetchell the Picture (Video) is sharp. I add a picture over there. — David, Feb 16 '19 at 16:27
Maybe W10 camera app is applying some sharpening filter. I don't run Windows, but can you check if there's some configuration option in that application to enable or disable filters? — Guille, Feb 16 '19 at 16:39
it's most likely a bandwidth problem. you need to ask for MJPG video. I've provided an answer. — Christoph Rackwitz, May 25 '23 at 20:54

score 0 · Answer 1 · answered Jul 27 '22 at 17:07

Typical camera pipelines have a sharpening filter applied to remove the effect of blurring caused by the scene being out of focus, or poor optics. My guess is that OpenCV is capturing the image closer to "raw" without adding the sharpening filter. You should be able to add a sharpening filter yourself. You can tell when a sharpening filter is applied as there will be a "ringing" artifact around high contrast edges.

Christoph Rackwitz · Answer 2 · 2023-05-25T20:55:49.730

This is very likely due to bandwidth limits imposed by the USB controller.

If you look closely, the image doesn't actually have 1920x1080 resolution. It appears upscaled.

You asked for Full HD at whatever default frame rate. This is impossible to move uncompressed over USB 2.0 High Speed.

That is why the camera picks some mode that fits within the bandwidth limits. This is often a low resolution mode, or sometimes a low framerate mode.

That is what you see here.

You need to tell OpenCV, besides the resolution, to tell the camera to compress the video.

MJPG is commonly available.

Try both of these. The order of the set calls matters:

cam.set(cv.CAP_PROP_FOURCC, cv.VideoWriter_fourcc(*"MJPG"))
cam.set(cv.CAP_PROP_FRAME_WIDTH, 1920)
cam.set(cv.CAP_PROP_FRAME_HEIGHT, 1080)

# OR

cam.set(cv.CAP_PROP_FRAME_WIDTH, 1920)
cam.set(cv.CAP_PROP_FRAME_HEIGHT, 1080)
cam.set(cv.CAP_PROP_FOURCC, cv.VideoWriter_fourcc(*"MJPG"))

Captured Image in OpenCV is unsharp

2 Answers2