Hi all!

I'm working on a series of articles that attempt to explain how GIMP's layer modes work and which situations you might use them in. I've just published the first article here:

GIMP's Layer Modes (Somewhat) Demystified – Part 1: Normal to Addition

If you have any additional information on how any particular layer mode works, or you have specific uses that I didn't mention for any of the modes in the article, please let me know. This is a group learning experience.

Keep Calm and GIMP On!

That's an excellent idea. It's been trial and error with me so far though I have got used to overlay, multiply and colour now and to a lesser degree, grain merge. I couldn't explain them though.

Heh I was gonna do something like this, but I wasn't sure how to do it.
I guess you figured it out! xD

In "dissolve" mode, Gimp takes a pixel at random on either layer, with a probability to take the pixel from the top layer equal to the opacity of that layer.

Thank you for mentioning that. I just took another zoomed in look at Dissolve mode. What looks like a pixel chosen from the lower layer is actually a transparent pixel in the upper layer. It's easier to notice if you hide all lower layers or have only one layer. The lower the opacity, the more transparent pixels you get.

I guess what you're saying is that the percentage of non-transparent pixels is the opacity percentage?

More specifically, the probability is equal to the opacity of the pixel after the pixel's original opacity, the layer's opacity setting, and the layermask have all been applied.

Cool example! Mind if I steal that?

Of course I don't mind.

Indeed...

Hi, these threads and some of the included links might be of some use to you in preparing your documents.
http://www.gimpchat.com/viewtopic.php?f=8&t=8405
http://www.gimpchat.com/viewtopic.php?f=8&t=6538
http://www.gimpchat.com/viewtopic.php?f=4&t=5131
http://en.wikipedia.org/wiki/Blend_modes
http://www.northlite.net/ps/blend.htm
http://photoblogstop.com/photoshop/photoshop-blend-modes-explained

Thanks! I'll check them out.

I just updated the Dissolve section with Saul's example. (Thanks!)

Hi all!

I just posted Part 2 on GIMP's layer modes here:

GIMP's Layer Modes (Somewhat) Demystified – Part 2: Darken Only to Subtract

Please let me know if you notice anything incorrect or missing, or if you know of any good examples of usage for any of these layer modes.

Keep Calm and GIMP On!

Thanks, DebiDalio. Your explanation is very usefull. I learned a lot of new tips.

You're welcome! I'm learning a lot myself as I write these articles.

About darken only
Its effect is not so complicate as you describe , the use is the most intuitive and simple BUT very difficult to understand if the top layer is solid grey or even a greysh gradient as in your example

I prefer another example
1 Get a picture of a intense but cloudless sky as BG layer
2 on top add a picture with very dark clouds AND with the sky colour BRIGHTER then the sky in the layer below

In darken only mode this combination will show the sky of the BG layer combined with the dark clouds from the top layer



So Darken only do not modify colors, IT only totally (totally at 100% opacity) REPLACE colors , if and when the colors above are darker
If are not darker then will not do anything at all

----------------------------------------------------------------------------

BTW Whiten Only does just the opposite !

so you may use to do the opposite : to add white clouds (on Top) to a dark sky (below)

PS
I hope my example clear but you have VERY good motives to be confused because linguistic reasons:
We read colors in a very different way then our computer

As example
1)White and Black may be the same identical "colour" as for hue and saturation , with only different luminosity

2)Blue will always look to our eye much darker then yellow , but for the computer they may have identical lightness ,more same yellow may be even darker of some blue even if our eyes would never believe this possible

3) confront Red Vs Black , White ,Grey and Brown ; they may have all identical hue and only different saturation (for grey) or only different luminosity (for white, black , red ...and even brown)

I hope to have not confused you more ... there is no way to know the hue or saturation of a pure black or white if not using the color eyedropper because any "color" will become pure white if brighten to the max, pure black if darkened to the max, only between this extremes hue and saturation may become perceptible to our eyes

Thank you for that example, PhotoComix. I tried a combo of two sky photos and saw the effect you're talking about. It's true that if the colors of the two layers are very close (for example, both layers are in the blue range), what you essentially get is the darker colors from the upper layer superimposed on the lower layer.

yes ,in that case the trick may be stretch the contrast on the top layer to get the sky more washed out then the sky in the bg

Hi all!

I just posted Part 3 on GIMP's layer modes here:

GIMP's Layer Modes (Somewhat) Demystified – Part 3: Grain Extract to Value

Please let me know if you notice anything incorrect or missing, or if you know of any good examples of usage for any of these layer modes.

Keep Calm and GIMP On!

Thanks DebiDalio, I hope you have a great holiday season!