As a dielectric filter is turned (tilted), is the cutoff (color) change gradual or stepped?

Question

There is an image on Wikipedia showing dielectric filters change the colour as they are tilted against incident light:

This image only has four frames. As you tilt a dielectric filter will the colour change be gradual or will it be abrupt? What sort of range of change can be expected?

Do all dielectric filters have this property, or do I have to search for a specific one? When I searched for places selling dielectric filters all I got was dichroic filters, and those do not seem to have the same property, but I've never held one in my hand.

Where do I get a filter that exhibits angle-of-incidence based colour change, inexpensively to use in experiments with colour? I would like to see how different objects look in different spectra. This is for use in one of my hobbies, which is painting, but my guess is that this could be useful as an experiment to physics students in general.

I have spent an hour browsing the internet and half an hour on the physics SE, but I have not found a similar question. Thanks for reading!

(edit: image link was wrong)

Answer 1

Based off @Farcher's comment.

The effect in question is actually a property of interference filters and dichroic filters. (I am unsure if dichroic filters are a subset or superset of dielectric filters)

The filter works by creating two paths for light to travel through the medium. As they exit the medium again, the light waves sum additively or destructively, depending on wavelength. Whether the mixing is destructive or constructive depends on the relation of the thickness of the dichroic layer to the wavelength. As you tilt the filter, you effectively change the thickness of the dichroic layer, while your light's wavelength stays the same, effectively changing the cutoff frequency of the filter. This is well illustrated by this illustration of a tunable optical filter, found on Wikipedia:

You can find dichroic filters cheaply on AliExpress. You can also use 3M Radiant Color Mirror Film as a dichroic filter, and it's inexpensive.