Confusion: Manual lens DoF scale vs DoF calculator on APS-C Locked

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halpsb New Member • Posts: 19
Confusion: Manual lens DoF scale vs DoF calculator on APS-C

Hi,

I am trying to understand why DoF calculators show different values for near & far DoF limits, compared to the markings on my lens itself.

Looking directly at the 28mm lens that is mounted on my Fujifilm X-Pro3, I see that if I set my focus distance at 2m, I get approximately 1.2m -> 5m in focus at f/8. However, a DoF calculator will show me a DoF near limit of 1.43m, and a DoF far limit of 3.35m if I specify that I have an APS-C type sensor. If I select, say, a Leica M10 instead, then the distances I expected appear. And this is what I do not understand.
Why does the sensor type matter at all when establishing the distances that are in focus? Aren't the depth of field and distances managed by the lens itself rather than the camera? Why would the fact that the image is then cropped impact these measurements?
I understand that the FoV differs between an APS-C and a Full Frame sensor, but aren't the focus distances equal before the crop happens?

I just received the MF lens today, but it seems to me that I can trust the on-lens scale, rather than the DoF calculator in order to know what will be in focus or not.

Any insight would be greatly appreciated.

Thanks

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