Question: When using depth of field and hyperfocal calculators, I get very different result versus the in-camera DoF preview of my Fujifilm X-M1.

For example:

With [DOFMaster](http://www.dofmaster.com/dofjs.html) (or any other online calculator), for a Fujifilm X-M1, with a focal length of 16mm and f-stop = 8, I am supposed to get hyperfocal distance at 1.62 meters with DoF from 0.81 meters to infinity.

If I use those settings on the camera, in-camera DoF preview shows that DoF is about from 1.2 to 2.5 meters.

What am I missing?

Answer: 
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> What am I missing?
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You're missing that Depth of Field is subjective. In actuality, there's only one plane that's in focus — everything else can't be. Then, there's an area around that plane that is indistinguishable from out of focus because it's beyond the technical limitations of your camera to distinguish from perfectly in-focus. But, that's often quite small, too. Outside of that, it's a matter of how much blur you're willing to consider in-focus.

Sounds like your camera is simply more strict than the numbers used by the online calculators. I'm not seeing the X-M1 in [DOFMaster](http://www.dofmaster.com/dofjs.html) as a pre-selected camera option, but I note that when choosing the X-Pro1 or X100, which use the same sensor, the calculator chooses a [circle of confusion](https://photo.stackexchange.com/questions/9024/what-is-the-circle-of-confusion) of 0.02 mm. That's giving me slightly different numbers than the near limit of 0.81 m which you say you get, but turns out I see that with a CoC of 0.019 mm, so I bet your other calculator is using that value for Fujifilm. (Or, it might just be rounding errors — with [TawbaWare's calculator](http://www.tawbaware.com/maxlyons/calc.htm) I get your values with CoC of 0.02 mm.)

On the other hand, if you chose a circle of confusion of around 0.007 mm, then you'll see values like Fujifilm is giving you in-camera. So, there's your answer in technical terms — Fujifilm has chosen a much more discerning value for CoC than the online calculators assume. (This value gives a hyperfocal distance of about 4.6 meters at 16mm and f/8, by the way.)
**Film Format Basis vs. Pixel Basis**

The depth of field (DoF) is the region in which, due to optical physics, a point has, on the film or the sensor, an image smaller than the size of the circle of confusion (CoC).

The CoC is "classically" determined from the accuracy of the human eye and the distance at which a given size image will be looked at, a common assumption is that the viewer will be at a distance equal to the diagonal of the image. This is the approach of the film format based DoF, taken by lens manufacturers *even Fujifilm takes this path for Fujifilm X lens* and DoF calculators. The CoC standard value for a full frame 24/36mm film is set to 0.03mm, and the equivalent CoC for a Fujifilm APS-C size is 0.02mm. 

But, in a digital camera, you can also have the other approach, you could set the CoC to get the maximum use of your sensor taking in account its pixel size. This is the path Fujifilm takes when it calibrates the CoC for the viewers DoF indicator at 0.007mm

On its latest camera X-Pro2 and X-T2, Fujifilm gives you the option to choose one or the other value : "Film Format Basis" / "Pixel Basis"