nospam
In article <g1qk1a9cme4d74qd7arhb888ip0vovsui7@4ax.com>, Eric Stevens <eric.stevens@sum.co.nz>wrote:

Savageduck
That wasn¹t too tough to find: Posted: Mon, 15 Sep 2014 13:44:18 -0500 Message ID: <8738bs2076.fld@barrow.com>

Wherein Floyd stated the following:

³A non-destructive workflow means you can *undo* and then *redo*.

That is not a reversible function.

For example, you can add sharpening with a high pass sharpen tool to an image, save it as a JPEG, send it to someone else, and they can use a blur tool to reverse the sharpen.

If the sharpening is done with UnsharpMask that cannot be done. USM is not reversible.²

Note, the words, ³save it as a JPEG,².

As I said, that genius Floyd did.

nospam
and that genius is completely wrong.

a non-destructive workflow doesn't 'destruct' so there's really nothing to 'undo'.

all of the adjustments are done en masse, with the item in question simply removed (or its parameters altered), which means it's never 'done'.

Eric Stevens
If it were never done, how come you think it can be undone?

nospam
it's not undone. it's redone with different parameters.

it's not a pixel level editor, it's a parametric editor.

do we have to go through the discussion about rendering again?