Photoshop layer which creates glow on edges

[FranWillett]

I'm making some amends on a poster for a client which was originally created by another designer. The original designer created what looks like a sort of 'glow' effect on just the edges of the images/elements in the poster by creating a layer as shown in the the attached and setting it to screen and 50% opacity. I can't for the life of me work out how they created this layer. To me it looks similar to a high pass layer but black and white but I tried this and I couldn't convert a high pass layer to black and white so I'm not sure if this is what they did. Any way if anyone has any ideas on how this layer is created I would be truely grateful. Thanks so much for your help!

[Semaphoric]

Maybe Filter > Stylize > Find Edges.

[Bojan Živković]

Or convert to BW then Filter Gallery > Stylize > Glowing Edges.

[LAMY2017 · Accepted solution]

Fran, Semaphoric is close. If the original was in color, it would have been converted to B&W, then Invert used to  complete the look.

[Stephen Marsh]

Or even the Filter > Other > Custom filter with an appropriate edge finding matrix/convolution kernel.

Dropbox - Custom Convolution Kernels.atn

Many of the custom filter settings were designed to isolate a single angle, so they need to be combined to include all angles. Therefore you would use the combined actions titled:

Detection Sampler: Roberts

Detection Sampler: CG Lineart

Detection Sampler: Prewitt

Detection Sampler: Robinson

Detection Sampler: Sobel

Detection Sampler: Kirsch

Detection Sampler: Scharr

There are many different actions in this action set "toolkit", not all of them are custom filter based.