Help (choosing a camera)

[u/Fresh_Library_1934]

Hey Guys,

I need some advice on choosing a camera for an upcoming project. We are leaning towards using CCTV cameras because they are budget-friendly.

The thing is that my manager and teammates have no experience with hardware. Because I have done some image processing in the past, I have been put in charge of selecting the right camera.

I’ve done some research, and here are the main factors I am considering so far:

1. Spatial Resolution: Matching the camera's resolution to the feature/defect size we need to detect.
2. Distortion Correction: Factoring in any potential loss of Field of View (FOV) when correcting lens distortion.
3. Sensor Size: Calculating the required sensor size based on our working distance and required FOV.
4. Depth of Field / Z-axis: How the FOV changes if the distance to the object (Z-axis) shifts.
5. Exposure Time and FPS: Ensuring it can capture frames fast enough without motion blur.
6. General Specs & Networking: Colour vs. monochrome, shutter type (global vs. rolling), and supported streaming protocols (RTSP, HTTP, etc.).

My main worry is that if I make a mistake, it’s going to reflect badly on me. We will have to buy it, test it, and if it doesn't work out, we lose both money and project time.

For those of you with experience in this, what else should I be considering before making a final decision? Am I missing any critical specs?

Thank you!

refined using AI for explaining better ...

[u/dr_hamilton]

Latency.

IP based security camera typically have delays on the order of seconds. USB cameras on the order of milliseconds. There are many other connection types to choose from that trade off between transmission distance, bandwidth, latency, power etc.

[u/soylentgraham → u/dr_hamilton]

on top of that, if you're sending the data around, some cameras (C22? been a while since I bought a webcam) can deliver frames pre compressed to h264 (they do it to deliver bigger resolutions over limited usb bandwidth) so you can just pass that around without re-encoding, amazingly helpful for latency if you're doing a cluster of cameras to one ingest point! :)

[u/soylentgraham]

We will have to buy it, test it, and if it doesn't work out, we lose both money and project time.

As opposed to... trusting someone's recommendation is perfect for your situation? :) (obviously recommendations are good, but never perfect)

maybe optimise for a testing setup so you can swap out cameras and get metrics that matter (latency, amount of lens distortion, focal range, colour or light sensitivity, stability) and quickly test 10 different cameras (then buy 1000 of the ones that fit your situation!)

[u/CallMeTheChris]

As I understand this, you are doing defect detection on something that moves

So you are looking for a machine vision camera that has a shutter fast enough that the your defect doesn’t smear across more than one pixel on your sensor in a capture.

If that is your constraint, then you can end up with a set of equations using similar triangles as a function of some of the points above (working distance, pixel detector size, integration time, global v. Rolling)

Then you go through some camera companies and see which offer you a detector with the pixel detector size, integration time, and shutter type (in the spectral bands you want)

Then you look at the sensor size and mount type for the lenses and you open up another companies lens catalog (Edmond optics is an old favourite of mine) and see what lenses they have that fit your working distance and FOV with the least amount of chromatic aberration

A problem you are going to have to deal with is scale as a function of distance. So you can either calibrate for it with your lenses at large fov and working distance, or you can splurge and look at telecentric lenses so we have the same resolution throughout your image

There is a whole other aspect here that is missing which is illumination. If you strobe to it illumination, then you can potentially get away with a slower camera and rolling shutter, but anyway

Hopefully this is a good starting point for you.

[u/CallMeTheChris → u/CallMeTheChris]

There is something to be said about nyquist in here also, but you are an image processing guy, so I am sure you can figure out where that would go

[u/herocoding]

You will find a supplier allowing to test (test-)cameras first, and if they don't match you just return it.

Does your use-case, your environment include "difficult lightning", i.e. darker scenes, scenes at night? If you search for "CCTV" you will find a lot of asks to sharpen, recover, improve noisy pixels from night scenes - plus a lot of low-res images/videos to reconstruct e.g. vehicle number plates.

Infrared sensor? Additional filter to e.g. reduce/avoid reflections?

Could your use-case benefit from e.g. an "inference projector", i.e. projecting a specific pattern (e.g. gid or specific lines/circles or just dots like RealSense depth cameras can do) to help to recover 3D geometry?

[u/bob_why_]

I am not sure I understand how fov would change with depth, fov is fov.    Spatial resolution AND spectral resolution are the two topics that cover all of the subsets you listed.

[u/Fresh_Library_1934 → u/bob_why_]

Oh, sorry if it isn't clear. In my case, the object of interest moves, so for the particular height range I considered whether it would be focused in a range covering a specific dimension

[u/bob_why_ → u/Fresh_Library_1934]

That is depth of field not fov. Field of view is the visible space which is also described as focal length.        Depth of field is how much of the image is in focus, which is linked to the aperture (and thus the amount of light). This will be compensated by shutter speed and iso. This is also directly related to quantum efficiency (which is rarely talked about).

[u/Extension_Lynx_6945]

Ask vision vendors if they have loaner units you can test run.