Technique to mimic Screen Blending?

Hi All -

I've got an image of a lightning strike on a black background. I want to remove the black background, so that only the lightning itself remains.

By setting the layer to Screen blending mode, it accomplishes exactly what I want -- but only when atop other layers. I need to export just the lightning with an alpha channel to use in a Flash movie I'm creating, so that doesn't do me any good!

So the question is -- how do I get the effect of Screen blending without any underlying layers???

I've tried a few "remove black" filters, but they always take away too much of the lightning, and leave what's left with a dingy grey halo...

Please help! I need to deliver this tomorrow!

MindSpyder

I am not sure I totally understand what you want but here goes.

Make a new layer underneath the screened lightning level and turn off all visable layers but the two layers (the new layer and the lightning layer), then Ctrl+Shift+E (merge all). Hopefully you should be left with a bolt of lightning on a transparent background.

Oh and welcome to the forum, just shout back if you need more help or if this was not the effect that you were after.

Welcome to TPS!
I'd select the luminosity of the image, and use it as a mask:
1) double-click on your background layer so it becomes a regular one.
2) CTRL+Click on the composite channel (or do CTRL+ALT+~) to load that composite as a selection
3) click on the layer mask icon.
voila!
You can fine tune with a small blur+levels on the layer mask and/or with minimum/maximum

thehermit, do you also post at CA forums?

Busted! (and casually surf citizen art :p )

Hey sPECtre -

Unfortunately that techique produces the same grey halo as the "remove black" filters I've tried... i've uploaded the file here (47KB) so you can see what I mean.

Currently, the bold shows only as white against the blue background... I want to be able to turn off the background and still have only the white, without any grey!

Thanks,

MindSpyder

P.S. hermit, your idea doesn't work because you can use Screen over a transparent layer...

That's why I said that you may need to use levels or curves on the mask... Photoshop is not a one-click program, you still need to perform some actions ;)

Another solution is to CTRL+Click on the channel with the best contrast...

Ok, I'll try typing this again.

Unfortunately you are going to lose more lightning than you'd like with a alpha channel, but if you use levels or curves to brighten the image until the lightning bolt is significantly larger than normal, then you might have better luck removing the background and still retaining the lightning. Try using the background eraser (with the lightning as a layer to erase to transparency) the background eraser is usually very good about leaching the background color (black) from the foreground subject ( lightning). but it will still remove more than you'd like.

Oh I forgot. you could also go into the Lightning layers' layer properties dialog box and use the blending sliders at the bottom og the blend mode tab. if you bring the black slider on the top bar to the right it will drop away most of the black, if you then alt drag on the same slider it will fade into the white, until the black background is all but removed. If you need to make the transparency permanent (which you do) make an empty layer below the lightning layer and merge the lightning layer down onto the transparent layer. I hope you cna understand this, cause re-reading it is making my eyes go crossed.