I want to use Field Blur but I do not want do that on my primary layer. I wish to use a secondary layer so I can safely edit that layer. But can it be done without having to create copies of the layers I want to blur? Is there any way to do that?
Select the layers you want to blur. And click
Convert for Smart Filters. This moves all the layers you selected to a new Smart Object.
Blur Gallery >
The image is blurred non-destructively.
To open the original image, double click the Smart Object Layer. The layers you moved will be contained inside the Smart Object, and will be unaffected by the field blur. You can edit them there. When you have finished, close the smart object, and save the changes. The Smart Object will be updated in the main file.
Here are some screenshots. I created a Smart Object consisting of two layers: a text layer, and an image with a layer mask - and then applied a field blur to the Smart Object.
This is the main image file, you can see the Smart Object with Field Blur applied in the layers panel.
Double clicking on the Smart Object opens it, and shows the original layers, unblurred.
In Photoshop yes, if you use some third party plugin that creates the blurred layer for you. ON1 Focal Point is an quite old example. I still use it, but it has been discontinued as an independent program; it's today available only as a part of a bigger effect suite.
Something that maybe is interesting:
In principle *) nothing should prevent to develop a photo editing application where all operations are non destructive for safety and for ability to correct older adjustments. The latest ON1 stuff claims to have it realized, but I have not tried it due the system requirements for smooth operation.
*) A proof: Adobe Illustrator has at least 6 years been able to pile effects non-destructively onto an imported or pasted bitmap photo. Effects can be turned on/off, adjusted, removed or moved up/down in effect stack that resides in the Appearance panel. Unfortunately i don't know how to make local photo adjustments here; effects that I've found nondestructive, seem to be image-wide.