Hum... the original preview built by LR which has to happen shouldn't change just by converting to DNG. Keep in mind there are two previews at the start. One is built by the camera which is proprietary and replaced by a high quality one built by LR so there will always be differences. That initial camera generated preview isn't usable. I suspect that's what you're seeing and want to retain but you can't.
I'm not sure what the preview is that I"m seeing. I've attached a sample screenshot. When I import, I flag picked images, then I generate 1:1 Lr previews, then I proceed with editing. The preview on the left (I believe) is the original 1:1 Lr-generated preview. The camera preview would look like a JPG, and actually looked similar to my edit on the right.
I can convert all existing photos to DNG, then for each photo individually copy the settings, reset the photo, save DNG preview, then reapply then paste edits. That would restore the ability to view DNG's as below. But that's a very tedious process and seems incorrect.
When you first import, you should see a preview of course. Depending on a number of factors, a second or so later, you'll see it update and change. That's LR building it's own preview. As I said, converting to DNG shouldn’t change that a bit. The other possibility is you have some preset affecting the image upon import? You'd still see that change from the original camera generated preview but perhaps you are then altering it again with some additional setting? Bottom line is, I've never seen what you report in terms of a DNG conversion also altering the image preview.
I do this by pressing Y within the develop module.
So you are NOT talking about the camera-generated preview embedded in the raw file. You are talking about the Lightroom rendering prior to adjustments.
I am confused too - it seems converting to DNG does not change the behavior of 'Y' key, in my experience. In other words, in my experience, it does not change the "Before" settings used when doing before/after comparisons. But regardless - you can set the state for compare by context-clicking the "Import State" in edit-history and choose 'Copy History Settings to Before', then the 'Y' key should do what it did before. Also try '\' key if you haven't yet.
And you can choose any other step in edit history for comparison if you want.
Another idea: make a snapshot of all CR2 files prior to conversion, for convenience - you can also context-click snapshots to set basis of comparison (the 'Before' settings).
The only way I can view the original unprocessed photograph at this point is by Resetting the photo, and then undoing the Reset to restore my edits, or by creating a virtual copy and simply resetting it.
After pressing "Y" go to the bottom entry in the History list, "Import (date)", and click on it and you will have your before/after view.
True...selecting a different history point is simpler than Resetting and Undoing.
Basically what has happened is that the DNG is being generated from an already edited CR2 - so as far as LR is concerned, that edited CR2 file becomes the "original" "Before" picture in comparison view. And what I'm trying to do is keep the original unedited preview.
So using your idea, here's what I was able to do:
1. Convert already edited CR2 to DNG
2. Press Y to view comparisons
3. Select Original Import history state and it changes the "After" view to the unedited version
4. Right-click photo and Copy After Settings to Before.
5. Select the most recent history entry and the After image is changed back to the edited view.
Now if I can find a process to do this automatically, that would be awesome.
Thank you for the idea
that edited CR2 file becomes the "original" "Before" picture in comparison view.
Hmm - I could have sworn that didn't happen the first time I tried it (which I did as a test for your sake - I don't normally convert to DNG), but I just tried it again and was able to corroborate your experience: before state was set to current edited state, instead of staying at previously selected state.
Not sure what to say - if it's important you could probably find a way to automate, e.g. using auto-hotkey, sqlite, or a plugin.
Me? I change "before" state so often that it wouldn't be worth the trouble..
Note: there was a bug introduced in Lr5 whereby "before" state is frequently reset to current edited state when it shouldn't be - this may be another flavor of that same bug, and it's one reason I so frequently set "before" state, even if it is already set, or should be, to be sure..
I would like to see (the bug fixed and) a keyboard-modifier which always compares current state to imported state (and displays which state your comparing to), so there is not guessing which state your comparing to.. - a feature request?
The Preview is set to the state as of import which has just occurred due to the DNG conversion—we’re not looking at the original raw, anymore, since the DNG just came into existence. When a DNG is created, the embedded preview is the current settings, perhaps from an XMP or perhaps from the LR catalog.
I think the quickest way to do what you want is after converting to DNG is to enable the Before/After view (Y|Y), click Swap, click Reset, then click Swap again.
If you know the CR2s will be eventually converted to DNGs anyways, why not convert at the start of the workflow, at Import by selecting "Copy as DNG"? Saves time, simplifies things, avoids problems and you lose nothing. I convert at import because I like the internal XMP and the quick loading data, but the backup second copy remains in CR2.
I am trying to solve this for previously edited CR2 files as I'm trying to convert my whole catalog to DNG. Going forward, I will be converting to DNG upon import.