Saturday, March 7, 2020

Augmented Reality Depth of Field

The current Depth of Field Info script (DOFI) was written to be as un-intrusive as possible, whilst displaying the maximum (blur) info associated with focus, for example when undertaking manual focus bracketing or setting the infinity focus.

The latest version of ML DOFI, as usual downloadable from the link on the right, now includes an augmented reality (AR) option, that shows the focus and various key distances (3*hyperfocal (3*H), H, H/3, H/5, H/7) on the ground plane. That is at the optimum focus positions for focus stacking.

Of course, because the script doesn’t know the camera’s full orientation, this version assumes that the ground plane’s height is specified by the user and that the ground plane is parallel to the axis of the lens. In most cases the AR mode will be used with the camera on a tripod.

The AR mode can be switched on and off in DOFI’s menu.

To use the AR mode, first ensure you have the correct info set in the menu, ie tripod height and camera format.

After that, all you need to do is centre the display on the infinity horizon, ie level the camera. The AR mode shows infinity as a black dot.

To illustrate DOFI’s AR mode, this screen capture shows what the AR display looks like if you are focused short of the ground plane’s intersection with the lens field of view, ie the point of focus is hidden. 

Here we see the hyperfocal shown by the yellow dot with a green bar, and the 3*H distance. For infinity focusing, the sweet spot is between H and 3H, that is infinity blurs between the ML set Circle of Confusion and a third on this. Going less than a third of the CoC is not likely to gain you anything, as your defocus blur will be less than two sensor pixels.

In this next screen capture we have refocused towards infinity and the point of focus, as projected on the ground plane, is shown as a red dot, indicating it is less than the hyperfocal.

Finally, this screen capture shows the focus dot has turned green, indicating we are focused at greater than the hyperfocal. We also see we are focused less than 3*H.

As is the case with all DoF info, the AR mode is there to aid/inform focus setting. DOFI’s DoF and FoV calculations are based on a thin lens model and are a reasonable approximation away from the macro end, say, at H/7 or greater.

Finally, I welcome feedback, especially ideas that could make DOFI better.

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