Exporting from edited smart previews

[evikne71]

When I edit a smart preview and then export it as JPEG within the resolution of the smart preview, will the quality be exactly the same as if I exported from the original? Can an edited smart preview have all the same details without getting fresh, new information from the original? When I export from smart previews it goes much faster than when I have the originals available, so it feels like new (and maybe better) files are generated from the originals if possible.

[JohanElzenga]

I have never tested it, but I would think that exporting from the original gives better results. Especially noise reduction and sharpening should be better if you can downsample the edited original.

[Just Shoot Me · Accepted solution]

ernstv21515445  wrote

When I edit a smart preview and then export it as JPEG within the resolution of the smart preview, will the quality be exactly the same as if I exported from the original?

NO.

ernstv21515445  wrote

Can an edited smart preview have all the same details without getting fresh, new information from the original?

NO.

ernstv21515445  wrote

When I export from smart previews it goes much faster than when I have the originals available, so it feels like new (and maybe better) files are generated from the originals if possible.

Yes the SP is a much smaller file that does not contain all the detail the original contains. So an Export will go faster.

Yes you will get better detail from the original.

[Dale_Harper]

In addition to the above answers, I wanted to query something that I experienced recently:

I accidentally exported 500 images from my Lightroom catalogue WITHOUT the source images being attached. The originals were on an external SSD. I had rendered out SMART, STANDARD and 1:1 previews of the collection. I was exporting the images @ 3,400px (Long Edge).

1 - I noticed that the images exported at approx 890Kb/ Image. When I connected the SSD, the average file size was 1/6Mb (i.e more data).

2 - Why didn’t Lightroom warn me is the desired export quality would need to source images?

3 - Why couldn’t it pull this detail depth from the 1:1 preview?

Any ideas?

[Rob_Cullen]

1 - I noticed that the images exported at approx 890Kb/ Image. When I connected the SSD, the average file size was 1/6Mb (i.e more data).

To be expected as the 'connected' original has the full pixel dimensions to work with.

From a Smart Preview (2560 pixels long edge) an 'upscale' resample to 3,400px might not have the same detail.

The "Don't Enlarge" option, will also determine whether you get a 3,400px or a 2,560px long edge from a Smart Preview. If ticked, it over-rides the entered long edge amount.

2 - Why didn’t Lightroom warn me is the desired export quality would need to source images?

I have no idea (as another Lr user). and agree it is annoying (happened to me!).

Add your vote to- No warning before exporting files from smart previews | Photoshop Family Customer Community

3 - Why couldn’t it pull this detail depth from the 1:1 preview?

Possibly (I am guessing!) because the 1:1 preview may be created from the 2,560px Smart Preview, and not the original full-size file.

Which is also why it is suggested that Noise Reduction, Sharpening, Chromatic Aberration, etc, should only be done with the original full-size files attached.

[Dale_Harper]

Thank you! This all makes sense to me.

I didn't see the 'Don't Enlarge' checkbox and wasn't aware of the smart preview pixel dimensions.

Regarding point 3 - I appreciate the insight, but why on earth would someone render out 1:1's ( at a significant file size, if you track the preview files file size before and after), if they still ultimately needed the original images for sharpening and noise reduction? Why would anyone use 1:1's?

Many thanks for your input and advice!

[Rob_Cullen]

For some answers I refer you to the expert-

https://www.lightroomqueen.com/lightroom-performance-previews-caches/

I understand that 1:1 previews are used in the Library module. The Develop module creates its own 1:1 preview only when needed, which is why I suspect that the Develop module will make its 1:1 view from the Smart Preview (if the original full-size file is not available)

[JohanElzenga]

Dale_Harper  wrote

Thank you! This all makes sense to me.

I didn't see the 'Don't Enlarge' checkbox and wasn't aware of the smart preview pixel dimensions.

Regarding point 3 - I appreciate the insight, but why on earth would someone render out 1:1's ( at a significant file size, if you track the preview files file size before and after), if they still ultimately needed the original images for sharpening and noise reduction? Why would anyone use 1:1's?

Many thanks for your input and advice!

The library module uses its own (AdobeRGB) previews. You render a 1:1 preview so you can see the detail at 100%. The images that are exported are rendered from the raw files (or the smart previews if those raw files are unavailable), and so that has nothing to do with the Library previews. Lightroom also starts from a wider color space for this export rendering.

Yes, in theory Adobe could have added a way of getting extra detail from 1:1 Library previews, if these happen to be present and if you are exporting with only smart previews present. It chose not to do that for obvious reasons: first of all those 1:1 previews are AdobeRGB and the image is rendered from data with a larger color space. Secondly those 1:1 previews may not be up to date anymore. They need to be re-rendered after each subsequent edit and maybe your last edits were done with only the smart previews available. That‘s a lot of ”ifs” and a lot of situations where this wouldn’t work satisfactory anyway, and so it would have been a waste of developer time.

[evikne71]

Thank you, both!

As I suspected, it's better not to be too lazy when exporting. Connecting the external HD with the originals will give the best result.