Calculator for Macro

[tartar]

Hello,

I'm glad to discovered this website. (Sorry for my English, I am French…)
While browsing the “photography tools” section, I wonder if there are any errors in the calculations. Or more precisely, I wonder if they are still valid for Hybrid camera:
For example, on the “macro camera lenses” page, if I use the “Magnification Calculator” tool, it tells me that the focusing distance must be at least 4 times the focal length of the lens. However, if we take the Nikkor MC 105mm for example, this is not valid, because the focusing distance is 290mm (1x magnification).

Another example:
On the "Macro Extension Tubes & Close-Up Lenses" page, I don't get the same results as in reality with "Extension Tube Calculator":
I have the Nikkor MC 105mm macro lens and 29mm extension tube. Using the calculator it tells me that I get a magnification of 1.28X. While in reality, I get a magnification of 1.64 (22mm filling the width of my 36mm sensor, mounted on a Nikon Z6).
Is this difference explained by the difference in draw/Tirage (space between sensor and lens) a reflex (46.5 mm) and a hybrid (16mm)?

Could you tell me if I'm making a mistake?

Thank you!

[odds]

...it tells me that the focusing distance must be at least 4 times the focal length of the lens. However, if we take the Nikkor MC 105mm for example, this is not valid, because the focusing distance is 290mm (1x magnification).

I guess the nominal 105mm is valid when focused at infinity. Lenses tend to shorten the focal length when focusing closer. The 4x rule implies a reduction from f=105mm to f = 290/4 = 72.5mm at 1x. I believe the shortening, or "breathing" depends on lens design and I do not know if 105 to 72.5 is valid for your lens.

A couple of links:
https://photographylife.com/focus-breathing
https://www.dpreview.com/forums/post/65840489
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Odd S.