Converting Blend effect into Transparency

DP
Posted By
Dox_Price
Mar 5, 2004
Views
319
Replies
9
Status
Closed
I have a single layer showing a semi-transparent object against a black background, and would like to remove the black background to leave just the object against transparency.

(Believe me, I’ve looked through all the FAQs and none of them deal with this.)

I can see the desired effect by placing a solid-color layer below, and then setting the top layer blending mode to Screen. But I need to make the layer look that way with Normal blending… so that when I hide the background layer, the transparency grid shows through.

I tried spreading the bottom end of the blending range for "This Layer" in Blending Options, but the effect is not the same – it is too dark and loses the subtle details.
Related Tags
blend conversion effect transparency

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CW
Colin_Walls
Mar 5, 2004
Must be missing something, but why can’t you just select the black and delete it?
DP
Dox_Price
Mar 5, 2004
The problem I’m having is with selecting the black.

Say you start with solid black and then paint white onto it ranging from 30% to 50% opacity, then flatten. How would you then isolate just the 30% to 50% opacity white on its own layer?
CW
Colin_Walls
Mar 5, 2004
The problem I’m having is with selecting the black

Magic wand, then Select Similar?
JM
John_Mensinger
Mar 5, 2004
Dox,

If I understand your situation correctly, here’s what I’d do…

Use the magic wand to select all the black outside the object you want to keep, and delete it, (the black).

Now to get rid of the underlying black in your kept area, duplicate the layer and move the new copy below the original in the stacking order. Lock the layer’s transparency and fill it with neutral gray, (128, 128, 128). Set the top layer’s blend mode to Lighten. Merge the two layers. Adjust opacity as desired.

This is theoretical, and assumes that the area you want kept consists of colors that are all lighter than 128, 128, 128. If not, fill with a darker gray, (darker than all the colors you want preserved).

I think this will give you what you want.

John
DP
Dox_Price
Mar 5, 2004
No, actually I want to keep ALL non-black colors, but only as their difference from black. For example, if one pixel’s color could be described as "black with 25% red added," then that pixel should become "transparent with 25% opaque red added."

White remains white, black becomes transparent, and shades of gray or color become the same hue with value and saturation translated into an opacity of full value and saturation.
JM
John_Mensinger
Mar 5, 2004
Ok, I did realize that what you want as an end result is the same as what you’d have if your object layer had never been merged with the underlying black, and I won’t say it’s impossible to get there, but there’s no universal method for achieving that…and certainly no "conversion," in the true sense of the word. I was trying to get you close via what really amounts to trickery and compromise.

Depending on the nature of the image, (remember you’re the only one who has seen it), and with some work, it may be possible to isolate each color one at a time and rectify the effects of it having been merged with black.

There’s no easy answer to your problem, otherwise you would likely have already gotten it here.
DP
Dox_Price
Mar 5, 2004
If there was an easy answer to my problem, I wouldn’t have registered in these forums. 🙂

I figured out an acceptable conversion that is at least artistically similar to what I’m looking for:

In Blending Options, spread the left end of This Layer completely. Copy Merged and paste to a new layer. Adjust Levels, drag the left end of Output Levels most of the way to the right.
H
Hexebah
Mar 5, 2004
Have you tried a Luminosity selection? Ctrl+Alt+Click the RGB Composite Channel’s thumbnail to load the lumiosity as a selection. Copy/paste to a new layer or use the selection to create a layer mask remove the black.

Chip
L
LenHewitt
Mar 6, 2004
Dox,

You will need to merge down and then delete the surrounding black. The layer needs that black beneath it for the blending mode to be able to blend to that colour.

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