P: Lens Corrections defaults not correct if Previews are "Embedded & Sidecar"

I'm reluctant to suggest using 'Embedded & Sidecar' since the Lens Profile issue being discussed here appears related to the issues John R. Ellis  mentions above. I feel it is prudent advice. If you or anyone else has confidence that it's NOT causing any problems  on your LR system (including the ones John mentions) then by all means go ahead and use it.

I tested both Embedded & Sidecar Preview Import with Lens Profile excluded from the Default Develop Settings and then Standard Preview Import with Lens Profile included. Embedded and sidecar was actually significantly slower (34%) with 'Generate Previews in Parallel' NOT checked. With it checked Embedded and sidecar was slightly faster (5.3%), but not much! I'm sticking with 'Standard' Import Preview Building setting. YMMV, so test it for yourself.

71 Canon 5D MKII CR2 (21 Megapixel) raw files with 2560 px Medium Standard Preview

Generate Previews in Parallel NOT checked
Embedded & Sidecar w/o Lens Profile: 63 sec.
Standard Preview with Lens Profile: 47 sec.

Generate Previews in Parallel checked
Embedded & Sidecar w/o Lens Profile: 38 sec.
Standard Preview with Lens Profile: 40 sec.

I disagree with your last conclusion. Importing using ‘embedded & sidecar’ still has the advantage that the import process itself is much faster. After the images have been imported, you can click on the double arrow icon of one of them, and then select the option to build standard-sized previews for all these images. You may have to apply a develop preset to get it to work correctly, so here is the trick: create a develop preset that applies the lens corrections and use that. As I said at the beginning, this is how I work and I do not experience the problem of missing profiles.

I checked my LR catalog using John R. Ellis Any Filter plugin and it appears running 'Build Standard-Sized Previews' "fixes" the Embedded & Sidecar and Minimal Import Preview  issue and the other two issues he mentions above.

In addition any image files that have outdated or no Standard preview should be rebuilt anyhow to maintain performance. Files that are up to date or have never been edited in the Develop module will not be rebuilt and don’t affect the preview building overhead. Here's how:

1) To speed the preview building process go to menu Edit> Preferences> Performance and check 'Generate Previews in Parallel.' Close and restart LR to apply this setting change.

2) In the Library module Catalog panel (left-side) select 'All Photographs.' This will allow checking and rebuilding previews for ALL of the files in the catalog.

3) Go to menu Library> Previews> 'Build Standard-Sized Previews.' This can take hours and will make your system sluggish so you may want to run it overnight.

NOTE: If LR appears sluggish when editing images after completing the preview building process you may want to uncheck 'Generate Previews in Parallel.' Try it both ways and decide for yourself.

Going forward the ‘Standard’ Build Previews selection should be used in the Import module until this issue is fixed.

I have tested with a single Canon 5D4 RAW file and get the same results, even when Previews is set to Minimal.

Import RAW file. Switch to Develop module get "Unable to load lens profile." error. Switch to Library and navigate to a different folder. Go back to original file and switch to Develop, lens profile information is now filled in and the error is gone.

After poking around at this for quite a bit with Todd, looking at Lens Profile field values via the plugin SDK, I think this bug is related to two other long-standing bugs:

- When you sync Lens Profile Corrections with a batch of photos, the SDK returns invalid values for the Lens Profile Name until you force the previews to be re-rendered by scrolling or rebuilding previews.  
https://feedback.photoshop.com/photoshop_family/topics/lightroom-sdk-photo-getdevelopsettings-return...

- When you apply Auto to a batch of photos, subsequent changes to Develop settings can be lost unless you first cause the previews to be re-rendered by scrolling or rebuilding previews.
https://feedback.photoshop.com/photoshop_family/topics/applying-auto-tone-to-a-batch-of-photos-loses...

It appears that LR has an internal architecture where for some batch operations like Auto and assigning lens profiles, it marks the photos with an annotation that the operation should be computed "when needed" in the future, but doesn't actually do the computation. This allows the batch operation to complete quickly. But other parts of LR forget to check for that "when needed" annotation and get confused.

"The Develop module should never show the embedded preview."

It's not showing the embedded preview in the Develop module. Just to be clear it correctly shows the Develop preview, but without the Lens Profile applied.

"However that new Develop preview does not replace the (embedded) one of the Library module either."

When switching back to the Library module with NO settings applied in the Develop module the Library module creates a standard preview with the 'Default Develop Settings' applied and the 'Embedded Preview' is removed.

"The Library preview is only re-rendered when you have applied edits"

In previous versions of LR (prior to 7.5) the Embedded Preview would remain in the Library module until an actual Develop setting adjustment was applied to the image.

"and I think that simply switching to the develop module is already seen as such (perhaps to avoid confusion)."

This is actually not the issue of concern here and if Adobe changed this behavior it is just an undocumented change. I'll take it either way!

Just to be clear the real issue is that when using 'Embedded & Sidecar' the LR 'Default Develop Settings' for Lens Profile are not being respected when 'Enable Profile Corrections' is a part of those settings. In fact an error condition is created, "Unable to load lens profile."

“Merely viewing the image in the Develop module without applying any adjustment settings should not cause LR to discard the Embeded & Sidecar Preview and rebuild a new preview.”

Actually, it’s a bit more complicated. The develop module uses its own previews, which are not the same as the previews in the Library and other modules. So switching to the develop module should always cause Lightroom to show you a new preview. The Develop module should never show the embedded preview. However that new Develop preview does not replace the (embedded) one of the Library module either. The Library preview is only re-rendered when you have applied edits, and I think that simply switching to the develop module is already seen as such (perhaps to avoid confusion).

I’m sure you see what you see. I don’t doubt that. As I’m typing this on my iPad, I cannot verify your findings. All I can say is that in my workflow I do not have any problems of lens corrections not being applied, probably because the preset forces Lightroom to update its rendering (it also applies auto tone). I never get into the situation where I have switched to the develop module and then still see the embedded preview. When I switch to the develop module, I see a Lightroom rendered preview (with correctly applied lens corrections).

Nicholas, I do agree it is a bug and this is the correct place to report it. I've added my 'Me To' which is the best way to get Adobe's attention.

I never apply Develop presets on Import, but just tried it. Using 'Embedded & Sidecar' preview setting and a Develop preset that applies 'Lens Profile' and 'Chromatic Aberration' settings the Embedded preview is retained as you stated. My apology! However, I still see the issue being discussed her. When I switch to the Develop module 'Lens Profile' shows as 'None' and message 'Unable to load lens profile' (see screenshot below).

Please try the test as I outlined in my last reply and see if you can replicate the issue. Thank you!