[Making a layer effect its own layer.]

Order is important.

1) Dupe the layer

2) Add the effect

3) In the full Layer FX panel (Click the 'FX' in the layer palette if you can't see it), reduce the fill opacity to 0 (as per GarryP's image in Nov 9 post above ^^^)

4) Close the effects panel

You should now have a layer that you can move around that has the shadow, but no wife.  If that's all you want, STOP THERE.

If you now want to play with that shadow as pixels...

5) Right click the 'effected' layer and choose 'Rasterise'

6) UNTICK 'Preserve Layer FX' in the dialog.  (Feels wrong.  But trust me.)

7) Click 'Rasterise'

You'll now have a pixel layer that just has the shadow pixels in it, which you can select, cut, paste, whatever:

 

One last thing: Don't make the same mistake as me, and forget to deselect the 'Fill knocks out shadow' box when initially creating the effect on the duplicated layer, if you don't want the shadow to have the holes in it caused by the pixels casting the shadow:

 

Deselected:

Selected:

 

[Making a layer effect its own layer.]

Sooo, yeah - Rasterisation works!

If you want to rasterise an effect, start by duplicating the layer, and reducing the fill opacity to 0 (as above).  This will just have the effect pixels on screen, without the elements that cause them.

Then you can rasterise this new layer.  There's an option to 'preserve effects'.  If you select it, the rasterisation will leave the effect in place as a layer effect, and just rasterise the invisible pixels.  If you *de*select it, the effect will be rasterised as well, creating the pixel-result of the effect as a separate layer for you to play with.

[Making a layer effect its own layer.]

Quote

If you separated the drop shadow from an image (or any other type of layer), what would it be the shadow of and how would the software know what shape it should be?

It wouldn't be a drop shadow to anything - it would be a bunch of shaded pixels.   The result would be to rasterise the effect so that each pixel would just be modifying the layers below it, as if the effect had been applied (So in your example, the layer would just contain a bunch of black pixels in a reverse L shape at 50% alpha.

It's handy to produce unusual effects - glitches, offsets, and so on.  The app does the hard word of creating the pixels, and then you can play with them in interesting ways - warp them, chop bits out, and so on.

But your fill opacity tip is very handy.  That gets a lot of the way there (and you may be able to then rasterise the layer anyway, and get all the way - I haven't played with it yet)

Thanks!