Ideal Pinhole Camera consistency

asked 2020-07-10 07:39:42 -0500

Wimpos gravatar image

updated 2020-07-13 05:26:19 -0500

Hi All

I am attempting to get the ideal pinhole camera for the camera of an iPad Mini 4. I have done multiple calibration sessions using a chessboard pattern and code from: https://docs.opencv.org/master/dc/dbb...

The issue I have is the consistency. I have used up to 200 images per session. The checkerboard is detected in all of them. The resolution of the images is 2448 × 3264 Auto-focus is turned off.

I find the deviation rather large, for the same camera.

fov_deg    59.2862
fov_deg    60.6048
fov_deg    59.9288

f_x    2913.33
f_x    2907.07
f_x    2933.18 

f_y    2914.59
f_y    2901.48
f_y    2930.74

c_x    1238.07
c_x    1282.58
c_x    1275.43

c_y    1605.38
c_y    1568.35
c_y    1574.36

Is this expected? Which accuracy is realistic? Am I missing something?

This data is later used for 3D reconstruction, so it should be as accurate as possible.

Looking forward to your insights

Best regards Wim

Edit: added info about auto-focus Edit2: corrected image resolution

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Comments

I _think_ that is expected, especially if the pinhole is an attachment over the device's autofocus optics. The device's camera is so small and its chassis flexible that even slight vibrations and warming of the device would cause such deviation. And for pinhole photography it might not matter much...

mvuori gravatar imagemvuori ( 2020-07-10 10:18:03 -0500 )edit

The pinhole in photography is used but the problem here is the autofocus from my perspective, i Think. And yeah, moreover there are also other problems, from my study the only problem about the temperature is the position of the piercing point in most of the camera and it start to be important when the temperature change of about 30 degrees. There is a paper about that. For this case it seems to be completely wrong. cx it is around 1238, sound strange to me...

HYPEREGO gravatar imageHYPEREGO ( 2020-07-10 13:24:47 -0500 )edit

Hi, forgot to mention that autofocus is turned off here. The image resolution is wrong, it must be 2448 × 3264

Wimpos gravatar imageWimpos ( 2020-07-13 04:56:59 -0500 )edit