Sorry, it took me a while to answer this one, because I was 'focusing'
on other things (with the excuse of the joke).

> Please elaborate how exactly you can utilize the Circle of confusion
> to check focus during shooting?

> What formula binds the CoC with the sensor format? It is more like a
> property of a lens... though I could find a table with sensor formats.

The CoC is one of the values to calculate the Hyperfocal distance
(http://www.dofmaster.com/equations.html), which in its turn is the
basis for calculating the Near and Far distances of "acceptable
sharpness".

According to Wikipedia
(http://en.wikipedia.org/wiki/Circle_of_confusion), the CoC is
calculated using the frame diagonal, so it would be directly related
to the sensor/film (if this is case, then Elphel's CoC

The software I posted the link will do the maths for us in field,
because we won't have internet there. I was planning to do a script to
do that, but then I decided to check if anyone had already done it. It
was a nice surprise.

As to how we'll use it, well, we have a simple problem: we will have a
camera operator in the setting; its signal will be sent to the
director and the director of photography via LAN cable to a central
computer; then it is sent back to the camera operator via wi-fi to a
smartphone, that will be used as viewfinder. That means the camera
won't be able to change nor check the focus without the calculations -
he will need to do the focus pulling previously. That's the reason.

It may be arguable that by using a tablet instead of a smartphone this
problem wouldn't be as critical. A better wifi hardware would provide
a better preview (bandwidth and processing power) for the viewfinder.
Even so, that probably wouldn't be enough to tense our nerves, which
will throw us back to relying on the maths. =)

Oleg, I'll check the focus helper, thanks for the link.

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