Sandman
In article <fntn1a581ourokq4njadqmm0crm60u711s@4ax.com>, Eric Stevens wrote:

Eric Stevens
All they have done up to this point is create a list of edits and view a simulacrum of their effect in screen. They haven't actually edited the image.

Sandman
Yes, they have. All adjustments are being applied to a preview file as you do them. The original file is untouched at *all times*, at no point in time is it edited in any way.

Eric Stevens
At least until you export. Even then the riginal isnot touched: it's all done to a copy.

Sandman
That's what I just said. All adjustments you do are always done to the pixels of a preview file on disk. Exporting is not a paremeter. The original file is always left untouched.

1. Open Image.NEF 2. LR creates preview JPG file on disk 3. Change Saturation +1 4. LR updates preview JPG file on disk

"Export" doesn't change anything. There is always an original file and a file with adjustments added.

Same with Photoshop and smart filters. All filters are added in the program and the original image data is kept intact at all times. If you "export" it from Photoshop in an image format that supports smart filters (such as TIFF), the reciever can reverse the process at any time, since the original image data is kept 100% intact.

Eric Stevens
I don't know enough to comment on that.

Sandman
I know. That's the *entire point*. You know nothing about these things, yet here you are arguing.

nospam
they resume working on the image and decide to reverse what they did the day before.

Eric Stevens
So they change the list of edits and againview the changed simulacrum which results.

Sandman
No "simulacrum" involved, Eric. Stop using words you don't understand.

Eric Stevens
You called it a preview file. Either way - I'm happy.

Sandman
You shouldn't be. A simulacrum is a representation of something else. Like a voodoo doll or a scale model. A simulacrum is an imitation. The preview file is exactly like the would-be exported JPG file. It's the same. Nothing is different.

In fact, you can export JPG's from LR that are *lesser* than the preview file, which would be the simulacrum if anything.

Eric Stevens
They haven't actually created any image to be changed at either point. That oonly happens once they execute the list of edits by exporting the image.

Sandman
Incorrect. Do you really think that Lightroom will display thousands of edited images in grid view by applying all adjustments in realtime? Of course not. All adjustments are applied to preview files that are saved to disk. That's the image data you're looking at.

Eric Stevens
But it's not the same as the file you would - say - send to a printer.

Sandman
It could be, sure. It's an ordinary JPG, and most printer drivers can handle them just fine. Again, you don't know what you're talking about.

The *only* point Lightroom loads the original file and applies the rendering chain in RAM is when you're viewing an image in 100% zoom.

Eric Stevens
Or when you export the image.

Sandman
Depends on how you export it. If you export it as a low-res highly compressed JPG, it can use the preview file. Chances are that it doesn't, but it certainly could, since the preview file *is* the current pixel data of the image.

nospam
with a non-destructive workflow, they can do that. without a non-destructive workflow, the changes cannot be reversed.

Eric Stevens
Once they have executed the list of edits by exporting a file the changes can't generally be reversed either.

Sandman
Sure they can, the original file is untouched and everything can be reversed.

Eric Stevens
The exported file is an edited copy of the original file.

Sandman
The original file remains untouched, regardless of how many times you export versions of it - hence everything is 100% reversible.

Eric Stevens
You are proposing producing a differently edited copy of the original file. That's not reversing an edit: that's a new edit.

Sandman
Incorrect - I am correctly stating that everything you do in LR is 100% reversible.

Eric Stevens
And I have pointed out that you cannot reverse a change which has not actually been made. Even if it is reversible, you can't reverse something before you have done it.

nospam
the change *has* been made, just not to the pixels themselves.

Eric Stevens
And to what has the change been made?

Sandman
To the pixels. nospam is incorrect here. All LR adjustments are applied to a preview file and saved to disk.

Eric Stevens
Except when you export.

Sandman
When you export, the preview file has already been made. You can not export a file from LR that does not have a preview file.

nospam
as i said, you're confused.

Eric Stevens
I'm confused?

Sandman
Very much so.

Eric Stevens
I think we are all confused.

Sandman
No, only you. This post is case in point - you know absolutely nothing about these things.