Cineversity

Dear friends I hope that someone can help me. I am photographer and new to 3D programs.
I do have a photo shoot on a white background with no walls around.
However I know the focal length, shooting distance and sensor size.
My question is: what se the correct method to find the camera position in Cinema 4D in this case?
Thanks in advance to all of you!

Hi Morg,

The Camera Calibrator is the tool to go. Please have a look at the scene file below, and the screenshot.
https://www.amazon.com/clouddrive/share/fzwcIwRJBJtRjaEjbUOBZ8iOJePYASTV4X21Gh9Ww6F

I have placed a cube around the sofa, to test my result. As there are mostly soft lines, the result might be a little bit off.
I would highly suggest to use always a completely non-cropped image, so the middle point of the image is defined naturally, etc.
Large card-boxes normally help, if the shot is done with a tripod, one with, one without card-boxes (lined up to X,Y,Z).

Tutorials are here:
https://www.cineversity.com/vidplaytut/victorian_house_set_extension_with_projection_man_camera_calibration
https://www.cineversity.com/vidplaytut/the_camera_calibrator_tag

For extreme cases, I have developed a little tool, which can be build with anything one normally find in most households.
In the case of a sofa, perhaps with much rounder contours even, I would use the four corners of it. The key is to create a “virtual cube”. After calibrating, the real image, shot from the very same position (tripod, not moved) is used, while the helper images are not longer in the scene. Same position, same lens, same focal point (lenses breath, i.e. after changing focus some lenses magnify stronger or less, just enough to render the results unusable.

Here is my idea:
Camera Projection with CINEMA 4D—03c
https://youtu.be/e6hcHz93fow

Besides that, if you have measured the exact nodal point position of your lens, and the point of interest (image middle point / focus – hence the non-cropped image as well), then one can recreate the scene in C4D, while using the Attribute Manager of the selected object to recreate the set up. Note that by default, things in Cinema 4D have zero lens distortion, and the used image should be corrected for the work in C4D. But the rendered result might be distorted to match the original shot, to keep the quality high. If you compose a render into a real image, I have a series here:
https://www.cineversity.com/vidplaylist/integration1/

I hope that helps, please let me know if you have any questions, I’m happy to look into it.
All the best

Dear Dr. Sassi,
Thanks you so much for your reply….it has open my mind….!
I did not know that a cropped image was going to effect the result of the camera position!
For this reason I am including the full version (with no cropping) of the photo.
It would be very interesting to verify the difference!
Thank you so much again!

Morgs.

You’re very welcome, Morgs, thanks for the nice feedback.

The resolution of 800x600 is very small, but it blurs some details. I guess your original is much larger, and will provide a better result.

Here is the one with the non-cropped. Slightly different, but given the “soft-target” of a sofa. As I mentioned, it might be a little bit off.
https://www.amazon.com/clouddrive/share/WTodlzIZHAVThqUT9nxtvc2NJR5K5PClQ5DwXpseJj7
I have taken both screen shots, so you can compare them directly.

What stands out is the offset. No idea where it comes from. It doesn’t look like a Tilt-Shift or even a Free-Camera result.
The lens looks more like a 50mm (in 36x24mm sensor terms). So the second “session” comes closer to my estimation.

My best wishes for your project.

Thanks you so much for your answer.
I do apologise for the size of the photo, but that was the maximum size that I was allowed to upload!
In fact the original is about 11.600 pixel wide!
Because you have been using far to low resolution the result of given by the camera calibration tool are a bit approximate.
If you wish I can send you the jpeg version of the high resolution and we can test and see in the result match the
effective parameters that I have used in taking the photo.
If you are agree on the above we can experiment as it will be very interesting to verify how the resolution can have an impact
in getting accurate result!
Thanks again for your reply.

Morgs.

Thanks, Morgs, for the offer.

Yes, I can do that, to set set up a new file and do it the third time
Please check your Private Message here on Cineversity, I have send you an upload link.
No problem and I’m happy to play.
How about you doing it as well?
Since there are only a few “sharp” elements on the sofa, things might never match the precision of the reality.

Let’s see how that goes!

All the best

I am trying just now!!!
It will be interesting ro compare the result!
At the end of this I will tel you exactly how the photo was shot!
OF course there are to few elements that will give us hard time to sole this “enigma”....
How can I send you the high resolution file?

Regards.

Morgs, please check your Private Messages here on Cineversity. Scroll up to the top of this page and in the middle (slightly to the right) there is a link option to access your private messages. I have send an upload link vai this option to your inbox.

Talk to you soon.

Morgs, thanks for the image.

The offset showed up in a similar way, which makes me wonder, is that the direct jpg export from the raw image? It feels corrected, like in: all verticals are parallel instead of having a third vanishing point way above the sofa. Hard to tell, to say the least. Perhaps just too little to be useable …
If that is the case, (corrected or too parallel) , the precision is limited for camera calibration. The meta data told me what lens and camera it is, so I guess the lens distortion comment (from above) can be ignored to a larger degree than normal.( I have a similar mid format Zeiss lens and it is also without any obvious distortion.)
I switched off the 3VP calculation in the Tag’s “settings’, and all the problems vanished instantly.

So, here is your file, excluding the image, as it was labeled private (you have to relink the image).  …_21.c4d
https://www.amazon.com/clouddrive/share/Gu7EucG4WQyqFPLzWX4gMaDyTT1szIVNwxwOvmRziW

I got 81.802mm (or 55.147mm if left in CC-default parameters: 36x24, or also called “35”).
The camera hight P.Y might be off, as I have zero data of anything, so I assumed 100cm for the depth (z) of the sofa side. It might be deeper/larger, but with 100 the adjustment is simple. In other words the camera Y position is certainly higher (which would result in a different rotation! So, don’t just lift the camera), around 75cm, would be my best guess (+/- 10cm)

My best wishes.

P.S.: IF you share the set-survey (the measured data), I will check if it is complete or sufficient to get a manual set up. Please note that a lens has to be measured, to get a exact nodal point (not where the sensor is nor the tripod center) as well as focal length, the printed focal length is most likely +/- 5% on an average.