LR2 and jpeg work

[liquidmonkey]

just wondering how jpeg data is stored when working in LR2.'?

i've done some adjustments on a few older jpegs and they look 'changed' in LR but when i look at them in the original folder using explorer they look 'unchanged' or original. plus there is no .xmp file.

before i go any further i'd like to know if (and when and how) LR writes the changes?

 

[Kiwigeoff]

The information is written into the header part of a jpeg file. If you have autowrite to xmp set in preferences it will be written on the fly, otherwise to see the changes in external apps you will need to cmd-s first.

 

[Brad Snyder]

To extend Geoff's thought, you will only see the changes in the XMP metadata in other app's. As you noted, the image that you see in other app's will remain unchanged. Because no other app's besides LR and ACR know what to do with the adjustment metadata.

What good is that? Well, it enables you to apply completely non-destuctive editing in jpegs. In LR, the adjustment metadata is very tiny in size, approx 15kB. To do the same non-destructive work in PS, you'd need multiple adjustment layers, each of which could add MB's to the PSD file size.

If you need to make the jpeg useful externally, and I assume you do, simply export it at the appropriate size and quality. This converts the adjustment data into real jpeg pixels which are again usable by other app's. Don't reimport it, just discard or archive it once you're done with it.

Now, if you need to make other adjustments, go back to the original in LR and tweak away. Then export again. This completely does away with the concerns over sequential compression losses in jpg files.

 

[liquidmonkey]

excellent explanation as per usual, thank you!!

i guess i'm a bit worried as to putting all my eggs into one basket if u know what i mean.
i have thousands of pictures and will slowly get them all organized into LR but it will take A LOT of time and i'd hate for that time to be wasted by an error with LR in the future.

but i guess that is a whole other issue...