Flatten or Collapse the History stack

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JBtheLD

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How does Lightroom arrive at the final edited state of a RAW file that has been processed?
  1. Does Lightroom just read the final history step of an image;
    or,
  2. Does Lightroom step through each of the history steps accumulating the edits of each step until it reaches the final state?
I'm asking this because (I think) the computer modelling package 3ds Max steps through the geometry modifier stack each time a model file is opened.
It is possible to collapse this "edit" stack to make the process more efficient when a return to earlier individual edit steps is no longer needed.
So, I was wondering if collapsing the "history stack" or removing it from one image or all the images in a catalog would make Lightroom faster to work with.
If so, how would I remove the history steps applied to one image or to an entire collection of images?
Would collapsing the history stack make the *.lrcat file smaller?

Thanks,

John
 
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I believe the current settings are stored separately from the history, so it only needs to check the current settings. Only current settings, not history, are written to xmp - the history is stored in the database.

Removing the history for each image (clear on the clear button on the history panel for each image - wow, that'd be a job!) may decrease your catalog size slightly, but considering it's only text data, I wouldn't expect it to make a noticeable difference.
 
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Thanks Victoria for your help,

Only current settings, not history, are written to xmp - the history is stored in the database.
By "database", do you mean the lrcat file? Are the history steps stored in the lrcat file?
My master.lrcat file is some 725MB in size referencing 59,''' RAW photos.
What makes the lrcat file itself so large?

but considering it's only text data, ...
But say there are 8 or 9 history steps on 59,''' photos, could that be a significant amount of text data for Lightroom to wade through?

clear on the clear button on the history panel for each image - wow, that'd be a job!
You're right, there would have to be a much slicker way of doing this. Perhaps, a new "Purge Database" command on the File Menu or a "Purge History States" in the Library Module would be needed?

Thanks,

John
 
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JBtheLD said:
Thanks Victoria for your help,

By "database", do you mean the lrcat file? Are the history steps stored in the lrcat file?

My master.lrcat file is some 725MB in size referencing 59,''' RAW photos.
What makes the lrcat file itself so large?

but considering it's only text data, ...
But say there are 8 or 9 history steps on 59,''' photos, could that be a significant amount of text data for Lightroom to wade through?
Click to expand...

Yes, the .lrcat file would contain the history steps. You could snoop around in there with a SQLite viewer, but .....

Do the math; 725,''',''' div by 59,''' = 12,288 bytes per image. I just picked a directory at random, and 172 XMP files averaged around 19kB.
I think the average XMP/metadata embedded in a JPG runs around 8-9kB (don't quote me, been a while since I experimented)
Seems like a lot of data, but 13kB is pretty efficient, considering it represents the full adjustment data on RAW files in the 5-2' MB range.

I'll take VB's word that rendering only addresses the "as-left" state of the adjustments, I'm speculating that means that saved History steps are simply pointers to data for re-rendering at user option, and otherwise don't add any overhead to the render process. I believe the engineers face an eternal struggle with performance improvement; I can't believe there's much of a performance hit, and disk space is cheaper every day.
 
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Thanks Brad,
I see what you mean.
I guess that's why non-destructive editing using "text instructions" is such an efficient way of editing an image.
It just feels that keeping the history states is like keeping every draft, alteration and ammendment of a piece of writing, when actually what is important is the finished article without all the clutter used to get to it.
The thing about the size of the lrcat file is that by most reckonings, I would suggest that a single file of 725MB is a pretty big file. Hypothetically, how long would PS3 or AutoCAD or Word take to open a file of that size?

Thanks,

John
 
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It's a database though John, and they're built for large amounts of data like that. PS3 has to read every pixel to open a file that big - a database just goes looking for the bit of information it needs.
 
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Victoria Bampton said:
It's a database though John, and they're built for large amounts of data like that. PS3 has to read every pixel to open a file that big - a database just goes looking for the bit of information it needs.
Click to expand...

Yes, it doesn't exactly open the whole file in one gulp .... as VB says database design is all about doing that efficiently, and not by brute force.
 
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Victoria and Brad,
Thank you both for your explanations.
So all in all that would mean that it makes (almost) no difference how many edits are carried out in a catalogue to the performance of the catalogue.
My 1,5'' photo catalog is much more responsive than my master 59,''' photo catalog.
So if the number of edits (the history stack) is irrelevant to Lightroom performance, it would imply that the big impact to Lightroom performance is the number of photos in the catalog.

Thinking out loud now....
So, I think from now on I will import each photo shoot into a new, blank catalog; process all the shots and then, only when all the edits are complete, import that catalog into my master catalog.
This route would mean that I can also work on individual small catalogs on my laptop while travelling, confident that all the photos in my master catalog are fully edited.
My master catalog would actually and effectively become an archive catalog.
Wow, for wedding photographers etc. their second shooters could supply their RAW negatives & fully processed images in their own catalogs. Is this what others are doing?

Thanks again,

John
 
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Brad and Victoria,
Thanks for the confirmation.
It seems to be working for me at the moment.
Lightroom has so many facilities to use that I haven't concentrated much on keywording just yet; I do add a few keywords to a shoot on import but that's all so far.
One day ... I will get up to speed on that aspect of Lightoom!

Thanks,

John
 
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