Reflect Blend Mode

[Scott Williams]

What is the 'Reflect' blend mode?

 

I may be a bit thick but I can't work it out :)

 

-Scott.

 

[gdenby]

I'm not entirely certain. I spent a week or so soon after get AD trying out the various blend modes, and combinations of them. From the samples I have, and some notes I made, my guess is that the "L" value of the blend layer in the HSL model is subtracted from  from the underlaying layer if the L quantity there is lower than 50%, but added to quantities above 50%.

 

In grey scale, that would mean a 25% L grey on top of a 75% grey would boost the to white, 100%, whereas the same object over one at 25% would drop to 0.

 

There might also be a luminance effect corrresponding to the perceptual bias of the human eye. Yellow is seen as more luminous than blue. Drawing from the above example, a light grey reflect blend over yellow would produce white, whereas over blue would shift toward black.

[kaffeeundsalz]

I would generally appreciate if the Affinity Help system could be a little more specific about what the individual blend modes do, both mathematically and what this means for the appearance of the layers. Right now, the "Layer blending" section only has a short description of the most commonly used blend modes, the other ones being just listed without further explanation.

[shojtsy]

I am also interested in a technical description of the formulas used in the blend modes, especially the ones introduced by Affinity. For example is Average same as Normal with 50% opacity? If yes, why would one need that blend mode?

[walt.farrell]

54 minutes ago, shojtsy said:

For example is Average same as Normal with 50% opacity? If yes, why would one need that blend mode?

No, they're different. In this picture, I have a red rectangle with two yellow rectangles overlapping it. Both yellow rectangles are the same color, but one used Average as the blending mode, and the other Normal with 50% opacity.

[v_kyr]

For the reflect blend mode take a look here.

[jenkm]

37 minutes ago, walt.farrell said:

No, they're different.

 

You're wrong, you get different results because your white background is not actually white, it is transparent. Blending with transparency is always performed in the Normal mode.

[walt.farrell]

Ah. Thanks, Yevgeny.

 

Why does it look white rather than checkerboarded?

[John Rostron]

Have you seen the link   from scaredycat. Look in the tutorials and search for blend modes.

John

 

[jenkm]

1 hour ago, walt.farrell said:

Why does it look white rather than checkerboard Ed?

 

Check the Document ▸ Transparent Background.

 

 

[shojtsy]

2 hours ago, Yevgeny Makarov said:

 

You're wrong, you get different results because your white background is not actually white, it is transparent. Blending with transparency is always performed in the Normal mode.

So Average and 50% Normal behaves differently in the presence of transparency. Good find. This seems to justify it's existence. I would go as far that the documentation for blend modes should include this information.

 

3 hours ago, v_kyr said:

For the reflect blend mode take a look here.

Thanks, I have read this earlier. But it doesn't help much to me, it is confusing and I was thinking about something more concrete. "Darkens the image using values from composite layer" can be told about a half a dozen blend modes. How this differs from them? Also "in Negation ... pixel values are simply added together" sounds exactly like a description of the Add blend mode instead. "flips the layer order, so it brightens the image using values from the composite layer" is also confusing, why would layer order change automatically lead to brightening independent of layer content?

Is the reason for Serif not publishing the actual blending formulas that these are some trade secrets?

 

[v_kyr]

Quote

...Is the reason for Serif not publishing the actual blending formulas that these are some trade secrets?

Don't know, maybe they are too lazy (or bad) in documenting certain things here. However take a look and search on the net for common used blending formulars, there a bunch of these and every better suited graphics prog book usually also shows the common algorithms used behind these.

[shojtsy]

1 hour ago, v_kyr said:

Don't know, maybe they are too lazy (or bad) in documenting certain things here. However take a look and search on the net for common used blending formulars, there a bunch of these and every better suited graphics prog book usually also shows the common algorithms used behind these.

For the photoshop ones yes. For example this is quite good http://photoblogstop.com/photoshop/photoshop-blend-modes-explained (but still not explain how Fill Opacity is used in the blending formula)

However for the Serif - introduced blend modes, they won't be found in these sites.

 

Edit: Your links lead me to this site which document the blend mode formulas of Pegtop, among them Reflect and Glow.

http://www.pegtop.net/delphi/articles/blendmodes/quadratic.htm

I have tested that they match the behavior of Affinity.

 

[v_kyr]

Beside those more algorithmic descriptions of the blend modes, also short illustrative examples are good suited to convey what these modes do (like shown here for Paint.net in their docu).

[jenkm]

15 hours ago, shojtsy said:

So Average and 50% Normal behaves differently in the presence of transparency. Good find. This seems to justify it's existence.

 

It's correct to say that the blend modes (all of them) don't work with transparency, there's just nothing to blend. But by itself, the Average and 50% Opacity are equivalent.

 

15 hours ago, shojtsy said:

Is the reason for Serif not publishing the actual blending formulas that these are some trade secrets?

 

They don't publish the formula because it's not useful to the average user. Looking at formulas you do not understand what will happen with the image.

 

If you want, you can find formulas here:

Adobe PDF reference, W3C CSS specification, perhaps even the source code of the GIMP and so on.

 

To understand blend modes, you need to look at their graphs (like on the Pegtop website), think of it as the Curves adjustment.

[dmstraker]

In contribution, I just posted a set of 2D blend examples. Check out the Reflect and Glow -- there's clearly a reversal going on here. The curve is interesting too, perhaps suggesting some multiplicative aspect of the function?

[jorismak]

Just discovered the Reflect mode, and I want to know how to do the same effect in Imagemagick / Vips / G'mic, so I want the formulas :). I'll take a look at the links posted here to see if I can figure it out.

 

What I discovered: If I take the luminance of my 'source layer', create a new layer filled with a yellow warming color, and use the luminance of my source layer as a mask, the reflect blend mode at 20% seems to do basically the same as Nik's very nice Color Effex 'Skylight' filter. It warms things up in a subtle way but also adds some saturation, but not so much in the shadows. Gives a very nice warming effect if your image was shot with clouds or pure in the shadows, or an auto-whitebalance made it 'too neutral / cool'. Way nicer than just adding a warming color with 'Soft Light', Photo Color Filter or other tricks.