Fe can be understood as shallow nuance, but also as a small incremental change of perspective. incremental in the sense that the change can not be divided up into parts that can themselves be understood independently.
F functions seem to have something to do with adjectives. they can be understood as registering a unique difference; one comprehensible only in terms of itself.
F = qualities
T = quantities
the human perceptual organ seems to bring perspectival input in a way that does not incorporate small enough changes for them to qualify as Fe. in a sense, the Fe is only arrived at mentally by dividing up the Te perspectival saccades. you see two images in sequence, too different to be suitable for direct association, then you find the pictures that should go in between them to form a smooth transition. the process by which this happens is crucial to understanding the system as a whole.
under entirely different circumstances the reverse happens. you take a picture and then latch together small, incremental changes so as to create a direct sequence of two disparate states, connected by an arbitrary transition, an analytical method of transiting from A to B. this is the process of deriving T from F. it happens not during perception but when forming plans and expectations of the future prior to observing it.
the two are opposites and non-interchangeable.
the challenge is figuring out how this relates to the N, T, S, F, N cycle and how this cycle is then ontologico-mathematically understood.