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10 votes
Accepted

Does the Quality of the Pictures Taken by a USB 3.0 Camera Depend on Cable Length?

No, the data in the USB cable is digital. Namely there is either an error in the data or the data is the same at any place along the cable.
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9 votes

How do I get the most accurate camera calibration?

I decided to post this answer here because a while back, this came up as the top result in Google and its suggestions helped me. So I decided to share my experience too. Having spent countless hours ...
  • 191
7 votes

How do I get the most accurate camera calibration?

Here is a list of 'best practices' for camera calibration which I originally posted here: https://calib.io/blogs/knowledge-base/calibration-best-practices Choose the right size calibration target. ...
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4 votes

Camera Calibration - why do you have to move the calibration board?

This is due to the optimization problem being rather high-dimensional (around 11 parameters). With only a single observation of the calibration board, there would be multiple possible combinations of ...
  • 146
4 votes

Detecting bullet holes using Python with camera or sensors

I can't really comment on the machine vision part, other than any question that asks "How do I do <some signal processing task> in <some language>" is fairly naive. The way you ...
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3 votes
Accepted

Can you average out focal length from different camera calibration sessions?

No, it is not a good idea. Typically, you want to limit the volume of space relative to the camera in which you want to do your measurements, and you want to use a single calibration target ...
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2 votes

What are characteristics of shadows in an image given an outdoor setting from an image processing point of view?

The characteristics of the shadow are as follows: It is always dark regardless of the color of the object or the color of the light used to make a shadow It only shows a dark outline of the object It ...
2 votes
Accepted

What are characteristics of shadows in an image given an outdoor setting from an image processing point of view?

Shadow has very specific properties that makes it very clear way of making it distinguishable from the regular object. A lot of work in the area of background subtraction and surveillance has been ...
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2 votes

What are characteristics of shadows in an image given an outdoor setting from an image processing point of view?

The edges of the shadows are crisper where they are nearer to the shadow caster. Also, since the sun is so far away, beams of light are essentially parallel when they reach us, which means that ...
2 votes

Camera calibration using multiple images

You are correct: to calibrate a camera you need a correspondence between 3D world points and 2D image points. The problem is that the 3D points cannot be co-planar, so people were building 3D ...
  • 4,941
2 votes

Where to get the Kodak PhotoCD raw image dataset?

http://r0k.us/graphics/kodak/ does link to Kodak PhotoCD contents with 2048x3072 images. It is not what is called "raw" as those are using 4:2:0 subsampling (so not lossless at all) and ...
2 votes
Accepted

Capturing images on fast moving conveyor belt

Try reducing exposure time if your camera allows that. With the short exposure time the conveyor belt should be well-lit. If that is not enough, a common solution is to use a flash which is ...
2 votes
Accepted

Camera calibration vs. registration

There is no matrix that maps a pixel in camera 1 to the corresponding pixel in camera 2. This is because the location of the corresponding pixel depends on the 3-D location of the corresponding point ...
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2 votes

How to estimate radial distortion from lens characteristics?

There is a lot of variability because distortion can be compensated for optically and lens designs differ. Some lenses are marketed as rectilinear, most not. You would be making the distortion worse ...
2 votes
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Oversampled Binary Image Sensor vs Active Pixel Sensor(CMOS)

The success of your camera depends on too many factors! and they're out of the scope of this page. If the dynamic range requirements of your application are not too demanding then you could take ...
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2 votes

Why is my laser beam intensity profile not Gaussian?

What could cause such a shape? Could it be due to the laser source which could not be perfectly single-mode? Or could it be due to the sensor? There is nothing particularly wrong with the "...
  • 10.2k
2 votes
Accepted

Pinhole camera model from houdini parameters

This is a long topic to fully explain. I will try to write shortly, so please excuse the brevity. Standard computer vision projection (ignoring distortion like Houdini) follows: $$ \mathbf{x} = \...
  • 5,255
2 votes
Accepted

Response function for digital camera pixel

If I understand you correctly, what you are asking for is called camera response function (CRF) and in general it is nonlinear and depends on camera device. For fixed device denote its CRF by $f$. ...
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2 votes

Fixing distortion in photographic reproductions

I answered a related question in SO some time ago. Briefly, you can work your setup through a standard camera calibration procedure, and you have the option of "freezing" the focal length to ...
1 vote

Why are two cameras mounted in paralle in stereo application?

When you say cameras are parallel it only means that the center pixels are parallel. Every pixel has a different angle, and that refers to the overlapping regions you were talking about. Actually ...
  • 471
1 vote

the position of image plane in optical imaging

I agree with user lxg that it is a notational difference, as for the pinhole camera we always have: $$S_2 = f$$ That is not necessarily true for a camera with a lens. A pinhole camera is not the ...
1 vote

camera movement calculation

Is what I'm after even possible? yes. Let's start with the simplification your camera was a perfect pinhole camera. For starters, imagine you pick an arbitrary point object in your scene. You then ...
1 vote

Oversampled Binary Image Sensor vs Active Pixel Sensor(CMOS)

At the time when the original question was asked, there was no hardware technology to physically construct an oversampled binary image sensor. Two years later - Technology is now slowly moving towards ...
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1 vote

Estimate camera generalized velocity from consecutive frames

The term you are looking for is Optical Flow and it is a very actively researched field along with (the also relevant here) Simultaneous Localisation and Mapping or SLAM Getting a robust velocity ...
  • 10.2k
1 vote

Estimate camera generalized velocity from consecutive frames

It's possible, but it takes some sophisticated processing to do it effectively in a general environment. First of all, you can only detect motion relative to what you can see in the field of view. ...
1 vote

Camera calibration using multiple images

So here are the answers to the questions: It's a good question. First, your calibration grid should somehow be "coded". For example, the OpenCV checkerboard pattern is a rectangle and the points are ...
  • 5,255
1 vote

How to Linearise an Input Image before applying Color Correction?

Your linearization gamma calculation does not take into account the correction matrix. You could do a combined numerical optimization of the pre-correction-matrix gamma adjustment, the correction ...
1 vote

What are characteristics of shadows in an image given an outdoor setting from an image processing point of view?

Shadows, despite what I have always assumed, are black or nearly so. In my studies with the LED light and the digital camera, I have discovered that the shadow, is, in fact, the color of the surface ...

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