For calculating DoF for any fixed set of viewing conditions (print size, viewing distance, visual acuity) there are only TWO more things you absolutely must need to know. The first is the Total Magnification ratio, that is the ratio of the size of the subject in real life (at the real world side plane of focus of the lens system), compared to the size of the subject in the final image. So a subject 20" high reproduced 10" high would have a reproduction ratio of 2:1 or 0.5×. The second thing required to be known is the absolute diameter of the aperture, not the f/number. Although it is possible to calculate DoF from these variables, what happens is that it will allow you to calculate a range of other variables that will produce the same results. As you decide on one of the calculated values to use, so the other choices of values become more constrained. Eventually it comes down to picking a subject distance a focal length (which defines f/number), and will also affect the final enlargement ratio.

Of course in practical photography one is usually limited by the equipment available. This will limit the size of the imaging area, perspective requirements will also limit the camera to subject distance. So we are now also limited to what focal length lens we can choose to frame the subject. Generally these will be overriding considerations, and it may well be that the DoF ends up being limited either wider or narrower than one would ideally like for artistic reasons thanks to limits in available equipment.

This applies the same whether we are looking at analogue or digital imaging, although both mediums have limits. For analogue imaging the limits are the size of the grains in the emulsion, both on the film and the printing paper, although the film grain is most likely to be the limiting factor. In digital imaging the limit is Nyquist. It will require that both the taking sensor, and the output device can operate within the relevant Nyquist limits for the required final viewing conditions. As long as one is operating within those limits the rules for DoF apply equally.

Alan