The problem with linear polarizers on cameras is not whether they are film or digital cameras. The problem arises from the fact that light reflected from a dielectric surface can be partially polarized (without using a polarizing filter). In fact early polarizers were just stacks of glass at angles that polarized the light.
Since light can be polarized on reflection, and since autofocus systems on cameras depended on light that was bounced around from mirrors and through various prisms to the autofocus sensor, the use of polarized light meant that the light that reached the autofocus system could be polarized in a different direction from unpolarized light that entered the camera. That could potentially cause errors in the autofocus system.
Using circularly polarized light mitigates this problem because circularly polarized light does not change polarization direction on reflection. That means that it acts like unpolarized light when it comes to the autofocus system. But since the outer half of a circular polarizer is a linear polarizer, it affects the light entering the camera just as a linear polarizer would. The second half of the circular polarizer is a quarter wave plate, which produces a quarter wave delay in one of the polarization components coming through the filter. This means the electric vector of the light wave is not constrained to one direction (as a linearly polarized wave would be) but has two components with a 90 degree phase difference, so the electric vector travels in a circular fashion. Hence the term 'circular polarization'.
https://www.uglyhedgehog.com/user-page?upnum=3002Autofocus systems were developed for film cameras late in the film era and digital cameras took them as a standard feature.
I suspect the effect on autofocus systems is small so that a linear polarizer will work on a modern camera. There is the possibility of focus errors, which I have not evaluated. I took a quick look a couple decades ago and didn't see any effect but it was not a real definitive study.
Note that a circularly polarizing filter will act as a linearly polarizing filter if it is reversed. The quarter wave plate will do nothing important to the light, leaving the linear polarizing component of the filter to do all the work.
Your Crown Graphic will work with either a circular or a linear polarizer (my old Speed Graphic did not have autofocus). Linear polarizers may be cheaper, but since circular polarizers are THE thing to use these days, linear polarizers may be in shorter supply (and therefore higher prices) than the circular polarizers.
PS: 'Disturbing patterns' probably refers to Moiré patterns, which arise from patterns in an image interfering with the square rectangular grid of sensors in a digital camera. They have nothing at all to do with polarizers. It is purely a geometric effect. It is not a problem with film because the film grain is arranged in a random pattern.
The problem with linear polarizers on cameras is n... (