Scope panel, intensity waveform

[NotMyFault]

Hi,

there is a mismatch between specification and implementation of scope panel and intensity waveform (and others like RGB Parade).

According to help:

Available charts

• Intensity Waveform—displays a scatter plot of the luminance values of pixels in an image. The X axis gives the horizontal location of the pixel while the Y axis provides its luminance value.

Observed:

For pixels with black, intensity (luminance) is shown as thick line at 100%. Expected: 0%

Screenshot is from iPad, same issue on Desktop.

 

intensity waveform.afphoto

[User_783649]

That’s actually very interesting! And what’s even more interesting, that there’s a little bug in the Color Picker that causes this problem. 

If you move sampler dot to the very black corner you’ll get H:0 S:100 L:0. I think it’s wrong. And the very black corner should actually be H:0 S:0 L:0

If you’ll move it tiny bit down from that, you’ll get H:0 S:0 L:0. Why S value getting changed from 0 to 100 here?

[NotMyFault]

The color sampling issue could be caused by the forced dithering of gradients. It leads to kind of colored noise added to the gradient, and if the picker is set to show values in percent, it could be rounded to HSL 0, 100, 0, in reality RGB 1,0,0 which looks almost black but is actually 100% saturated darkest possible red.

Use Info panel or color panel, set to rgb sliders, set to 8bit, to see the correct color value.

So this is unrelated to the issue I raised in this thread.

[User_783649]

I’m not sampling the color from the gradient. I’m manually set it via Color Picker. For both of the gradient points.

Try set the color of the black point of your gradient to H:0 S:0 L:0 and you’ll see that those will drop to 0% in Scope.

[NotMyFault]

Not on my Windows PC.

Whatever method i use:

• Fill layer with color set to RGB 0,0,0 or to HSL 0,0,0 or color wheel
• Procedural texture filter with RGB=0 and A=1
• Channel mixer with RGB=0 and ALPHA=1

The scope gets to 100% for all pixels who are totally fully black.

 

The scope panel updates without undue delay, so i can always see the line jump from almost 0 to 100 when i move the sliders.

[User_783649]

@NotMyFault Seems like another issue with Windows version of Affinity. I’ve just checked on Mac. Works as expected. Strange.

[NotMyFault]

Yes, platform depended bug

 

In my view the MacOS behavior is wrong too. H 0 L 0 should be intensity 0 (and not 100%) no matter what value S shows.

[User_783649]

3 minutes ago, NotMyFault said:

In my view the MacOS behavior is wrong too. H 0 L 0 should be intensity 0 (and not 100%) no matter what value S shows.

Absolutely! If L equals to 0 in both cases, there’s no influence of S can make on how Scope level is calculated for this area.

[Callum]

I believe this behaviour is currently logged with our developers to be fixed in the future.

[G0HLJ]

Changing to H0 S0 L1 puts the scope in the right place so they are 1 digit off