Hugin Lens Calibration GUI Instructions

[Drew Faber]

I'm having problems with the lens calibration instructions on page

http://hugin.sourceforge.net/docs/manual/Calibrate_lens_gui.html

Does anyone have any insight on how to enter the parameters on the attached screen?

I keep getting a warning: There are invalid values in the input boxes. But it doesn't say which input boxes. So, I'm just flying blind.

Thanks.

[T. Modes]

comp...@gmail.com schrieb am Dienstag, 8. März 2022 um 19:58:12 UTC+1:

Does anyone have any insight on how to enter the parameters on the attached screen?

I keep getting a warning: There are invalid values in the input boxes. But it doesn't say which input boxes. So, I'm just flying blind.

Thanks.

You need to enter the focal length multiplier. Normally it tries to read it from the EXIF, but when it is missing you need to enter manually.

[Drew Faber]

Is the focal length multiplier only used if using an extender?

Is my focal length multiplier 1 if just the original lens is used?

How do I figure out the best values for the other "Options?"

[T. Modes]

comp...@gmail.com schrieb am Mittwoch, 9. März 2022 um 17:20:07 UTC+1:

Is the focal length multiplier only used if using an extender?

Is my focal length multiplier 1 if just the original lens is used?

No. It is used for all lenses. A full frame camera has a focal length multiplier of 1.0.

Other lens systems have higher values. Sometimes the focal length multiplier is called crop factor.

How do I figure out the best values for the other "Options?"

In general the default parameters should be good enough. If your lines are short and therefore are not detected, you can decrease the minimum line length.

[Drew Faber]

I'm using a cell phone, the Nokia 6.1. I do not know if a crop factor other than 1 is needed.

I resized my image to be 1600 pixels across. Is that the right thing to do?

The option descriptions don't make any sense to me. As I said, I'm just flying blind trying to figure out what values to use.

Here is my calibration image, resized to be 1600 pixels across.

[Jeff Welty]

The  Nokia 6.1 has a 3.57mm focal length lens.   The sensor is 4.608mm wide by 3.456 high, so the diagonal (lower left to upper right) is 5.76mm.   On a full frame camera (old 35mm film), the diagonal is 43.27 mm.   The crop factor for the Nokia is 43.27/5.76 = 7.51

So the entries in the GUI should be 3.57mm for the focal length, with a crop factor of 7.51.   (The 35mm camera "equivalent focal length" is 3.57 * 7.51 or 26.8, so your entry of 27mm with a crop factor of 1 is very close to the same thing).

https://www.devicespecifications.com/en/model/9c3b4b96

https://www.gsmarena.com/nokia_6_1-8972.php

I'd personally not rescale the image to a smaller size, it won't affect the result from a math standpoint, but the more resolution the algorithm has to work with the better precision the answer should be.

[Drew Faber]

The default values for Options are not finding any lines. What should I try changing?