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

[NCARalph]

Windows 10 PS 23.0.1

I'm trying to make a stepped wedge. I selected the Black/White preset, set the smoothness to 0 and selected 'linear' for the method. I then used Image Posterize set to 8 steps. The result wasn't equal size boxes, they got bigger approaching white. If I select 'classic' I do get an equal sized and lightness spaced boxes. Looking at the gradiants before posturization the 'classic' is actually linear.

[Semaphoric]

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.

[Stephen Marsh]

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

[ClaudiaR99]

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

[Earth Oliver]

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?

[Semaphoric]

I first noticed the issue when putting gradients on a monochrome image,, so it's beyond color.

These are the histograms after applying a black to white, zero smoothing gradient to a 16-bit monochrome image.

Perceptual:

Linear:

Classic:

[Earth Oliver]

but what's the issue there?

[Earth Oliver]

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.

[JamesMork]

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.

[NCARalph]

Well, that might be true if someone for some reason set the gamma of the print to something other than 1. That certainly is not the case here, I never changed the gamma from the default 1. The gamma of 2.2 is generally a display setting, not a print or image setting.

In any case adjusting the gamma won't make the steps evenly spaced. Try it.

[JamesMork]

Hi, Ralph

I've attached a sample file for you to inspect. It contains a gradient applied with the "Linear" option (Smoothness=0% and dither=false), an Exposure adjustment layer applying 1/2.2 gamma correction, and a 16 level Posterize. A merged copy of the image is below. Hopefully this will help clarify the underlying interpolation.

Best regards,

James

[davescm]

"Well, that might be true if someone for some reason set the gamma of the print to something other than 1. That certainly is not the case here, I never changed the gamma from the default 1."

The gamma on the default colour spaces is rarely 1. sRGB is close to 2.2 (actually 2.4 with a short linear section at the start),  Adobe RGB is 2.2, ProPhoto is 1.8.

Dave