On Tuesday 02 October 2007 11:52:13 Patrick Shanahan wrote:
> * gimp_user <[EMAIL PROTECTED]> [10-02-07 13:47]:
>  Much unnecessary quote removed.....
> > One thing I forgot to mention is that if you are simply trying to edit an
> > image for your own use and can revisit the original then the absense of
> > non-destrucitve editing features may not be a handicap. The point is to
> > know what you can and cannot do with each and every toolset and when a
> > tool is appropriate to your needs and when it is not.
> You keep getting back to this "non-destructive editing".  WHO can edit
> an image for what-ever purpose and not retain the original?  HOW can
> you edit <anything> and not have a copy of <anything> to begin with?
Your question is a good one and the distinctions are sometimes simple, 
sometimes complex.

In this response I am going to try and explain my perception here. First the 
distinction between the original and the process of editing.

You are correct to point out that sensible processors will retain a copy of 
their original. Here your question   suggests a lack of clarity on my part. 

1. The term non-destructive editing is term that describes a process chosen 
for editing rather than the simple retainment of a copy of the original 
(which is simply a back up). 

2. There is no external authority who precisely defines what is and what is 
not non-destructive editing but it is a term in wide use and has a certain 
group of expectations attached to it that sometimes loosely and sometimes 
quite precisely define it.

3. The term Non-destructive editing is  generally taken to have a meaning that 
goes well beyond the simple keeping of a record of exactly what has been done 
at every stage so one can troll back through the record to recreate each 

4. The  non-destructive specific record from editing is not the same as a 
separate record of every action or stage in the process.

5. Now I will attempt to amplify.

Let us say we are beginning work on a basic image.

(a) I am not entirely happy with the exposure of the image as a whole. If I 
was editing destructively I would use a tool to change the exposure and the 
original image chnages accordingly. If I am editing non-destructively then I 
need a tool to help me. For example it could creates an entirely different 
layer that appears in a layer stack above the original image. This layer 
would hold instructs that would apply my adjustment to a selection of  layers 
that appear below the adjustment layer. However this is only stage one and 
does not quite yet meet current expectations of non-destructivenness. We have 
to be able to two further requirements:
       the ability to revisit the adjustment layer and tweak it at any later    
time (no matter how many subsequent changes have been made).
       The ability to turn on and off the effect. This is most important 
because it enables one to view the image with and without the effect at any 
subsequent time and also create other layers providing the same effect but 
applying different values.
(b) I now carry out many more edits each one of which is similarly handled.  
Furthermore when I close that image it can be reopened and all the adjustment 
layers are there for subsequent tweaking by \anyone to whom I choose to pass 
the file.

IF I can present a third party with a full copy of my work, and they can go 
back in and tweak each effect to their satifaction than I can honestly tell 
them the image has been editied non-destructively. However if they had to 
retrace my steps from the history then the edit would definitely not be 
regarded as non-destructive.

How is the record different?

Usually with non-destructive editing you have the history (which is the same 
as a record of every step). 

However more importantly the adjustment layers only record for each effect 
what actually modifies the original to produce  the final image. So the noise 
in the history from work that I did,  but discarded, does not clutter up the 
non-destructive editing record.

For example if I had adjusted the exposure up and down repeatedly the final 
adjustment layer would only hold my final setings rather then the ones I had 

However if I had two layers holding exposure adjustments I could have both 
affect the final record or either or none!

It is important to appreciate that for the professional interested in high 
quality images the image at the base of the stack will normally be the raw 
image stored at 16 bit per channel. However when one is working using HD the 
actual image could be 48 bit per channel as a result of combining three 
images to produce the base.

Gimp-user mailing list

Reply via email to