Are 'classic' and 'linear' gradient methods reversed?

The "Linear" option results in stops being interpolated in linear color space If you convert the results of Linear above back to gamma 1.0 space, you should see linear steps with posterize: 1. Layer -> New Adjustment Layer -> Exposure and 2. Set "Gamma Correction" to 0.4545. (inverse of ~2.2 gamma). 3. Posterize.

I believe the confusion here arises due to differing connotations of "Linear" (interpolated in linear color space vs. producing linear results in ~2.2 gamma space).

In this particular case of a black and white gradient the "Linear" method is not producing your desired results. For an example where "Linear" produces more desirable results, compare results between the three different methods for a gradient from pure saturated red to pure saturated green.

Before these new rendering options have more time to become established, i'd strongly advise Adobe to change the name of Linear interpolation. If it's confusing the experts, it'll definitely be confusing for everyone else too. And given that Linear is also a shape option, it's obvious where the confusion is originating.

Hey folks, so Linear refers to the interpolation of color and not the "shape" of the gradation. If you use a pure color (like 255, 0, 0) then draw a grad across your canvas, you'll see that the hue remains constant throughout the grad, whereas Perceptual will shift the hue. I'm not sure why Linear is the exponential shape it is, but i imagine it has something to do with color mixing when combining hues.
So to be clear, the interpolation dropdowns are only in reference to color interpolation, and have nothing to do with the "shape" of the gradient. Does that make sense?

Thank you for bringing this to our attention @NCARalph . We'll look into it and get back to you.

I'd suggest that you also add an equalize command after creating the gradient - before posterizing, even with classic settings.

If you campare the histograms of the two methods the difference is apparent. Classic has the same number of pixels for each value, but Linear gives more bright and fewer darker pixels. Classic sure looks and acts linear to me.