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: 
First, a [word](https://photo.stackexchange.com/a/34801/15871) about what depth-of-field is and is not:

> 
> **In a way, depth-of-field is an illusion.** There is only one plane of focus. Everything in front of or behind the point of focus is out
>  of focus to one degree or another. **What we call DoF is the area
>  where things *look, to our eyes, like they are in focus*.** This is
>  based on the ability of the human eye to resolve certain minute
>  differences at a particular distance. If the slightly out-of-focus
>  blur is smaller than our eye's capability to resolve the detail then
>  it appears to be in focus. ***When you magnify a portion of an image
>  by making it larger or moving closer to it you allow your eye to see
>  details that before were too close together to be seen by your eyes as
>  separate pieces of the image.***
> 
> 
> ***Since things are gradually blurrier the further they are from the point of focus, as you gradually magnify the image the perceived depth
>  of field gets narrower as the near and far points where your eyes can
>  resolve fine details moves closer to the focus plane.***
> 
> 
> 

Since depth-of-field is dependent upon viewing size and distance as well as the visual acuity of the viewer it is hard for a camera to indicate depth-of-field if it doesn't know what the display size of the photo will be. Any in-camera DoF measurement is going to be based upon an assumption regarding the eventual viewing conditions of the photograph.

Assuming the standard 8x10 viewed at 10 inches by a person with 20/20 vision is probably a little too broad in the current digital environment. But most of the online calculators still assume this standard viewing size and distance. If you expect to view images at a 1:1 pixel size on a computer monitor, the DoF for the same exact image will be much narrower. After all, viewing a 22MP or so image on a monitor with 96ppi pitch is like viewing a part of a 60x40 inch print!
**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"