Unreal How to Feed Images into Open CV Lens Distortion Calibrator

I’m currently trying to use the OpenCv Lens Distortion plugin that comes installed by default with the Virtual Production example in Unreal 4.27 to try and create a camera undistortion texture for my camera. So far I have had no issue getting this to work with by manually setting the lens distortion parameters (K[1-6], P1, P2, etc.) but now I want to automatically generate this data using a series of images from my camera. To do this I threw together a blueprint (couldn’t get access to OpenCV from C++ scripts) that takes a directory, grabs all jpg files and feeds them into the calibrator.

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Unfortunately no matter what I try the calibrator refuses to accept any of my test images, and since this is a blueprint I can’t really debug the problem any more, all I know is that the FeedImage node returns false for every image. I’ve tried searching for documentation or tutorials using OpenCV Lens Distortion but for some reason it is a completely undocumented feature besides a couple pages saying the nodes exist and 2 or 3 questions on this answer hub asking how to turn the distortion variables into a texture. If anyone knows what I might be missing please let me know.

enter image description here

Just for reference, here is a sample of one of my test images:

  • Board Width: 10
  • Board Height: 7
  • Square Size: 3.2727 cm

I was able to get OpenCV working directly in another program using a python script but I would like to have this working in Unreal to minimize the amount of programs needed. Obviously the functions are difference since Python deals directly with OpenCv while Unreal is using a blueprint wrapper but at least I know the images and calibrator settings should be valid.

I also want to mention I saw the Lens Distortion plugin mentioned in this post, but unfortunately it does not seem to have the ability to accept images to generate a lens distortion model, it simply builds one using the k1, k2, k3, p1, p2 parameters and camera matrix values.

How should a Dandelion chipped lens behave on a Nikon F5?

I’m running two Nikkor Ai lenses with dandelion chips on a Nikon D800. Both work great. I’ve recently started using a Nikon F5 film camera. The same lenses don’t give any aperture readout or indication they are recognised by the F5. The F5 is working with other modern off the shelf lenses. Can anyone confirm how the Nikon F5 should behave with dandelioned lenses? I was under the impression they should work but the chips can’t be programmed using the F5.

upgrading from kit lens [duplicate]

This question already has an answer here:

  • Lens upgrade paths (sub $ 1000) for the EF-S 18-55mm IS kit lens for Canon APS-C cameras [closed] 7 answers

Am bit new to DSLR .Interested in landscape

My problem

  1. I feel kit lens came along with my 650D is not giving me sharper images.(Culprit might be myself)
  2. Budget problem for upgrading to Canon lens
  3. Going back to my home country soon .So need to decide fast.Here things are cheaper comparatively.

My Options.

  1. Get rid of kit lens and buy Sigma 8-16mm-f45-56-dc-hsm AND 18-200mm-f35-63-ii-dc-os-hsm or 18-250mm-f35-63-dc-os-macro-hsm. Any inputs for above lens?Are these good?Is it worth buying ?
  2. buy Sigma 8-16mm-f45-56-dc-hsm and be happy with kit lens.
  3. Be happy with kit lens and learn more techniques.

Which option should I opt for ?

DSLR in AF mode. Do we need to use Focus ring on lens?

My camera is in Auto Focus mode (AF). As my understanding, the camera will focus on subject automatically. But when I rotate the focus ring, the focus subject points will change, too. I don’t understand why. As my understanding, Focus ring is only used when Manual focus (MF) used.

If I rotate focus ring in AF mode, does this hurt the camera or lens? My lens is Sony DT 18-135mm F3.5-5.6 SAM Zoom Lens. ( The User guide of the lens does not mention about AF & rotating focus ring issue).

How do I choose between 24-70 f/4 and 24-105 f/4 Canon lens?

I am getting a new medium range zoom lens for general use and occasional weddings. This new 24-70 f4 was top of my list until I watched this review:

Canon 24-70 f/4 L IS vs Canon 24-105 f/4 L IS – Fight!

The guy, who owns the “L” lens (??? They’re both “L” lenses -ed.), complains that 24-105 f4 is a sharper lens and he claimed that there are other people who feel the same, but I couldn’t find any other reviews complaining about this lens sharpness.

I don’t want the spec of the lens which I already know but is there anyone here who actually owns those lenses and is happy with the quality of 24-70 f/4 over 24-105 f/4? i.e. is it worth paying extra for 24-70 f4 over much cheaper 24-105 f/4?

[Update]

I went with 24-70 f2.8 II and been very happy ever since.

How wide does the front element of a lens has to be, given the focal length and the aperture?

Clearly, a lens with focal length F and aperture 1/f has to be at least F/f mm wide. Maybe a little more to accommodate for the angle of view. However, lenses tend to have wider front element that F/f. For example, my Sony 24-240 3.5-6.3 has filter thread 72 mm, and the front element is not much smaller than that. However, 240/6.3=39, so it would seem that, theoretically speaking, the front element shouldn’t have to be much wider than 39 mm, if one would account only for F/f.

Is there another physical reason for that? Just curious.