Waat is a 1:1 Preview

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patrickt

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I've seen them mentioned, mostly in the context of how long it takes to generate them. I told LR2 to generate 1:1 previews. After a few cups of coffee it was done. But, I don't know where they are or what they're for.
 
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I might be wrong, but from what I understand, a 1:1 preview is a preview where every pixel of the original image takes up one pixel of your screen... or "actual size" if you're familiar with photoshop.... versus being a "zoomed out" version allowing you to see the entire image.

Someone correct me if I'm wrong.
 
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NeuralMural said:
I might be wrong, but from what I understand, a 1:1 preview is a preview where every pixel of the original image takes up one pixel of your screen... or "actual size" if you're familiar with photoshop.... versus being a "zoomed out" version allowing you to see the entire image.

Someone correct me if I'm wrong.
Click to expand...

You are partly correct. If you generate 1:1 previews, Lightroom will load the images so that you can watch them fullsize (every pixel of the original image takes up one pixel of your screen, as you mentioned). You still have to zoom in yourself, but the advantage is that you don't have to wait for the image to be rendered.
 
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The downside is that they are huge, so if you never zoom in while in Library module (Develop uses the original file itself), then there's not a major advantage to 1:1 previews, other than the fact that the sharpening and noise reduction is applied to 1:1 previews and not Standard previews.
 
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Excellent point Victoria. I recommend that you set your preferences to dispose of the 1:1 previews after a while. They can eat up disk space and if, as Victoria points out, you never zoom in Library module (or very infrequently) there's no advantage to having them.

I have them go away after a time via preferences because I do zoom in Library module after importing a new shoot so I can examine some of the details in the shots and not have to wait for a render on each image. Just another workflow preference!
 
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The "1:1" in the preview context isn't about screen size -- it means the preview has the same pixel dimensions as the original.

As others have said, the advantage to generating them is that viewing zoomed-in in Loupe, Slideshow, and other views may be significantly faster. The downside is the time it takes to build them, and the space required to store them on disk.

Additionally, 1:1 previews go through the full rendering pipeline (including sharpening and noise reduction), while smaller previews get a streamlined processing pipeline in the name of speed (unless 1:1 previews are being generated at the same time, in which case the smaller previews are downsized from the 1:1 previews).
 
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genemcc said:
Excellent point Victoria. I recommend that you set your preferences to dispose of the 1:1 previews after a while. ...
Click to expand...

If I render 1:1 previews on import and only look at some of them at 1:1, will the ones I looked at "live longer" than the ones I don't view? Or will they all "go away" as a group on the time scale I specify in preferences?
 
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From my experience, it looks like it is based on the time they were created. Also, even if it is feasible for the underlying database to keep track of the "Last Time Used", I don't think Adobe choose to do so to keep things performance wise. Imagine going from image to image in Loupe, the system having to write new values each time in the database. Not talking about going forth and back for fast comparison...
 
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I couldn't say for sure, but I'd be inclined to say it works on last updated basis, as 1:1 previews are updated when you change Develop settings. Perhaps someone knows the definitive answer though.
 
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How LR keeps track of preview files is something I personally would like to know more about. There have been occasions reported where preview files seem to get "orphaned" and left behind in the previews folder when an image is removed from a catalog (or deleted from disk).

I had a previews folder of around 1'GB that contained preview files - last mod date of over a year ago - which should NOT have still been there. Even after I discarded 1:1 previews there were still many preview files left, taking up a large amount of disk space, for images that had been moved to another catalog or deleted from disk permanently. I had to delete my previews folder to finally bring the size on disk down to under 1GB. I also set LR to discard 1:1's after One Day, which there are downsides to from what I understand (for example, exporting web galleries seems to work better when previews are built for all the images in the gallery??), but for me it helps to keep my previews folder from growing out of control.

BTW, I'm still using LR 1.4.1, but have read threads of similar concerns for LR2. I'm still looking for more definitive info on how LR keeps track of the preview files and if/how preview files can get "orphaned" and left behind...
 
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Victoria Bampton;2341' said:
I couldn't say for sure, but I'd be inclined to say it works on last updated basis, as 1:1 previews are updated when you change Develop settings. Perhaps someone knows the definitive answer though.
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I think it is a mix of my previous post and yours Victoria. When I say "the time they were created", one should read "last modified time". As these are files like any other in the system... But I still don't think that just seeing/using those is resetting the counter. Keywording dot not modify them but color adjustments for example do for sure.
 
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My understanding is the time period set in preferences starts from "last update/modification".
The previews file however does not delete the 1:1's immediately if a file is removed to allow for undo's. Try deleting a file from LR and see how long it may take to have the preview file shrink.
 
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I also seem to remember that Lightroom is a little overly aggressive about holding on to the preview space even after deleting previews, but I'll have to check into that. Gurus, any recollections on that one?
 
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Only what you say, VB. I think all the explanations I've seen have been in very general terms and circumlocutions, e.g. "overly aggressive retention". We've had very little insight into any of the preview/cache mechanisms. (At least that I'm aware of.)
 
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You're most welcome!

The question "what is a 1:1 preview" is a somewhat complicated one. With so much disk space "at risk" I really want to know all I can about the subject. The FAQ particularly helped me with regards to when full-sized (1:1) previews WON'T get discarded.

On the side issue of "orphaned" preview files, it seems LR needs a way to keep better track of the preview files or a purge function (sort of like purge unused keywords) that will compare preview files and existing images in a catalog, and remove unmatched preview files. Deleting the previews folder is a very crude method of regaining disk space.

One other note, I am not sure if LR2.x handles previews the same way. I haven't read anything to suggest Adobe has changed anything, but am not sure (could have missed something ;))

Cheers
 
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