Trying to make a soft edged black frame.

[Philip27463971xr7c]

This must be so simple but it's eluding me.  Can someone please point me in the right direction, in terms of how best to achieve this?

Presently I have a black rectangle the size of my artboard.  There is a slightly smaller white rectangle on top, feathered.  I thought maybe I could combine these to make the white area transparrent and export with transparrency to use it as a soft edged mask in a media server.

I'm fine with exporting, but I'm struggling to combine the black and the white shape as one, to make the white area punch out.  I have been trying to use a knockout group but I think I misunderstood how this worked.

[Ton Frederiks · Accepted solution]

You could try to select both rectangles, white on top, and click Make Mask in the Opacity panel.

Clip unchecked, Invert Mask checked.

[Philip27463971xr7c]

That seems to have worked perfectly, thank you!

[Ton Frederiks]

Good to hear that helped.

[Jacob Bugge]

Philip,

My (mis)understanding your question is slightly different to that of Ton (soft edged mask), so I believe in these steps:

1) Set the Object>Blend>Blend Options>Spacing to Smooth or a sufficient number of Specified Steps to get a smooth transition from transparent to (solid) black,

2) Select the two rectangles and Object>Blend>Make,

3) Create the (Opacity) Mask as Ton said.

Edit: My (mis)understanding your question was a misunderstanding indeed, see below..

[Philip27463971xr7c]

Another excellent solution, thank you.  I will experiment with both techniques.  Thanks for the help!

[Jacob Bugge]

Sorry, Philip, I just realized my overlooking your having a feathered white rectangle, my wrongly assuming an underlying artwork, and my misreading the answer from Ton, so my suggestion above makes no sense.

Just go with the exquisite solution by Ton.