Curves picker not working as expected in channels

[dizzwave]

Hello,

I have just recently started getting into Affinity, and so far I'm really enjoying it! Today I wanted to try something a friend told me he does in Photoshop, but it appears (to me) to be buggy in Affinity.

• I have an image in Lab color mode.
• Create a curves adjustment layer (it shows as default the Lab "Master" channel).
• Switch to AOpponent channel in the curves dropdown.
• Click "Picker," pick a spot in the image, and drag slightly up/down to create a curve node.

What I would expect here is a node on the curve corresponding to where that pixel lies on the A channel's axis.. but instead I seemingly get a node corresponding to where it is on the L axis.

In other words.. If I pick a bright white cloud, I get a node way far to the right.. even though I've selected the A channel, not the L channel.  And if I pick a dark pixel, no matter the color, I get a node way far to the left.  If I pick a midtone pixel, I get a node near the middle. 

For fun, I converted my image to RGB mode and tried it with curves in RGB channels, and had the same result -- the picker picked seemingly based on pixel brightness, not channel value.

I hope this makes sense. Perhaps I'm missing something and this is not a bug.  :-)  Thanks for reading.

[Callum]

Hi Dizzwave,

Welcome to the forums

From what I can tell from your description it sounds like everything is working as expected the help defines the function of the Curves adjustment picker as the following:

Picker—allows you to drag on the image to modify the adjustment. The initial click will place a node on the curve in relation to the pixel selected. Dragging up will lighten the image while dragging down will darken it. The curve graph will update accordingly.

If you feel this is a bug could you possibly provide an example of what you are expecting to happen as I've had a play in PhotoShop with this feature and it seems to function very similar to ours.

Thanks

C

[lepr]

1 hour ago, Callum said:

could you possibly provide an example of what you are expecting to happen

An excellent example with expected and actual results was given in the opening post.

[dizzwave]

2 hours ago, Callum said:

could you possibly provide an example of what you are expecting to happen as I've had a play in PhotoShop with this feature and it seems to function very similar to ours.

Hi Callum,

Thanks so much for looking into it!  After I made this post, I actually made a more comprehensive example, then posted a video of how it works in Photoshop, in the bugs forum: 

We could move the conversation over there if that's easier. Sorry for any confusion from having two posts.