blend mode with multi blend function

It would be nice if I could set the blend mode for each layer in multi blend as is to get the effect your after you might still have to use individual blend modes maybe one layer you want screen while the third layer luminosity etc...

I desperately need this, even if it only has four layers. (You can call it 'SuperBlend' and leave MultiBlend as it is.)

I'll try to explain the difficulty I'm having with the current system...

Here's Photoshop's layers palate and the result of four layers all set to "lighten". (The first layer is partially transparent.)


The resulting 80 lightness is what I expected.



Now here's a simulation of FF's blend abilities. You must in effect "double up" if you want to blend more than two layers with a blending mode. In doing so you lose transparency information which completely changes the result in some instances.



The current filter I've been working on "stones" requires a blend of four layers very similar to this example. Without the enhanced capabilities the filter will lack the depth I hope to achieve.

*Download this photoshop file if you want to experiment for yourself.
http://uberzev.googlepages.com/example.psd

Vlad?

P.S. Looks like the damn forum is broken again.

No, just plain ugly. Not the results -- I meant the component itself. And also confusing.

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uberzev wrote: I'm only asking for this because there is no workaround available.

Cascading Blend components?

Technically, FF uses the same Blend formulas as Photoshop does, so all you have to do is to cascade the blends in the right order. The order is crucial.

Regarding your Photoshop example -- either you're measuring the resulting lightness incorrectly, or your last layer is not completely transparent. The result can't be 80% because the result of your example (both in Photoshop and FF) should be exactly the lightness of your brightest color, #3, which is, according to the color picker, 68%.

Lighten is a dumb conditional mode. It simply compares the RGB channels and chooses the brightest of the two channels for the result.

Please check your measurements or tell me the exact color and transparency of your last layer.

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Vladimir Golovin wrote: Or, which is better, attach the PSD file here -- we'll save tons of time.

Here...

http://uberzev.googlepages.com/example.psd

Merge layers 1&2 and then 3&4 and you'll note that the result is different than it was with four discreet layers.

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Vladimir Golovin wrote: Merge layers 1&2 and then 3&4

This is an incorrect order. See how it's done in my filter above. The correct order of merging is:

Merge 3&4.
Then merge the result with 2.
Then merge the result of the last merge with 1.

This merging in Photoshop results in exactly 80%.

Here's how it would look with a true multiblend....


Here's how it looks using the "cascade" method...

Please check your email Vlad.

The thing is what you've done is only added the alpha information at the last step. What I'm trying to get at is I will have to deal with opacity at every step and once you've blended once you've already lost some of it. \

I apologize that I'm doing a terrible job explaining this.

I noticed that you use Levels with very, very close black and white points -- this pushes the algorithm too close to the FPU precision boundaries, so you may get all kinds of weird stuff with this setup.

Again, blending has nothing to do with the errors you're getting.

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Vladimir Golovin wrote: Yes, it looks like there's indeed a problem, but I'm still unable to localize it. Most likely, it has to do with precision loss somewhere.

Yes there is a loss of precision (saturation data). Its inherent when using more than one step to blend multiple layers in this manner.

This problem is not "bug", as the result is expected given the situation.

IMO the best way to understand and test this is to actually code a true multiblend for FF and see if the workarounds accurately duplicate its functionality.

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Vladimir Golovin wrote: Can you provide me with layered blending examples that don't get close to precision boundaries which cannot be reproduced in FF?

Yes I can. The result would be correct if there was a true multiblend for the four offsets...



example3.ffxml

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Vladimir Golovin wrote: Yes, this example is better. I can see the flaw even without applying Levels. BTW, have you tried the same thing in Photoshop with a 16-bit image? (It's a shame that their 32-bit mode doesn't support layers). Posted: February

Yes, it works fine in Photoshop as long as the four layers are blended in one step.

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Vladimir Golovin wrote: Zev, the flaw is in your method, not in FF. Try the same thing on a 16-bit image in PS.

I already have tested it in Photoshop and it works. Scroll to the top of this page for an example. (Yeah I switched from Lighten to Darken, seems to matter for Photoshop but not in FF)

Anyway like I said before if you make a proper multiblend in FF you'll get the right results.

Vlad, while that might be a 'single blend' its not a, 'all at once' blend which is what this effect requires. You've broken it into two seperate merge steps there.

I'm trying to explain that the shadow data only lasts for one step. By 'cascading' or 'doubling up' or using any other alternate method to a 'all at once' blend there will be a loss of data.

Vlad, the method does have a flaw. You can duplicate the problem in Photoshop (by blending in 'two seperate steps' ala FF) which proves this fact.

This is why a new method is required, one that uses a true multiblend component. I've already demonstrated that this new method works correctly in Photoshop. Now I just need access to that capability in FF.

*I can see facts, I know this is frustrating. Trust me I might sound thick headed but I know what I'm talking about.

I took another look at your example -- rearranged the blending order into a proper cascade. Looks much better:

The picture above proves the fact that FF blending is CORRECT.

However, it also proves the fact that having everything rendered in double-precision floating point is bad for this particular effect.

When you do 'one-time' blends in Photoshop, it kills subtle changes in color due to its 8-bit precision.

When you do the same in FF, all these subtle changes are preserved, and when you use Levels, they ruin the effect you're trying to acheive:

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Vladimir Golovin wrote: I hate to sound like a broken record but coding the true MB in FF would be a usefull way to see if that functionality was truly redundant like you claim it is.

No it wont.
Reducing the precision from floating-point to 8-bit per channel would be.