# Previews confusion



## gYab61zH (May 12, 2019)

Hi,

I still find myself struggling with the various types of Previews in LR. I am on a 5K iMac and the auto Standard Preview generated on import is just short of 6000 by 4000, which is also the maximum size of my photos. When Standard Preview size and 1:1 are so close would I be better off simply generating 1:1 on import? Or should I set (if that is possible) the Standard Preview size to 6000x4000? In other words, what is the best strategy if the aim is to have 1:1 and why?


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## Califdan (May 13, 2019)

What is your motivation for wanting 1:1 previews?   

LR automatically generates previews of the correct size whenever it needs to.  The only advantage of generating bigger previews ahead of time is to consume the time required to create them before they are needed rather than when they are actually needed?  If you have a decently fast computer we're talking a second or two per image which is meaningless on an image by image bases (e.g. when you take an image over to the develop module, or step through images in the Loupe view) versus a significant amount of time when importing several hundred or thousand images at once.  Not to mention the extra space needed to store them.    

Smart Previews are something else again so are not included in my comment.


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## gYab61zH (May 13, 2019)

I do a lot of browsing and then even a 1-2 sec delay can be a bit of a bind. Besides, as I explained, I am trying to understand LR's previews. If the Standard Previews are just about the same size as 1:1 why not go for the latter? And how do standard previews relate to 1:1? Can't I set standard to 6000x4000 and thus give myself 1:1 without generating them separately?


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## Paul_DS256 (May 13, 2019)

This may help Lightroom Performance - Previews & Caches | The Lightroom Queen


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## Linwood Ferguson (May 13, 2019)

If standard are "just short of 6000x4000" I assume you have auto size set and a huge, huge, huge monitor? 

Standard previews generally are small, with auto set the size required to display filling your largest monitor but not zoomed.  That strategy by Adobe worked nicely when a big monitor was 1900-2400 on a side, but if your long side is 6000, then you are correct, standard and 1:1 start becoming the same.

The main differences I can think of in 1:1 are (a) normally they are bigger, and (2) they are automatically deleted leaving  the standard size behind.   Speculating a bit, if 1:1 is actually even a tiny bit bigger, then they are going to take up extra space.  What's an interesting question is what happens if literally standard = 1:1?  I have no idea.  You'd probably have to dig into the internal storage to see if it is storing a 1:1 and standard as two separate images in the preview pyramid even though redundant.  

Note you can force standard to be a different non-auto size.  If your actual display on your monitor is typically smaller (in a smaller window), this might still be adequate for display (LR won't rebuild it larger if it can display without needing a larger size).

What kind of monitor do you have, if I might ask, that is 6000 on a side?


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## Jim Wilde (May 13, 2019)

Ferguson said:


> (2) they are automatically deleted leaving  the standard size behind.


It's a little bit more complicated that that. If the user edits an image that already has a 1:1 preview built (such as during import), then yes that 1:1 preview is automatically deleted (as it's out of date as soon as the first edit is made). However, if after finishing editing an image, the user then builds a new 1:1 preview the subsequent disposition of that new 1:1 is determined by the user in the Catalog Settings>File Handling tab.....there it's possible to set a time period for automatic deletion of the 1:1s, but one of the options for deletion is "Never".


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## Johan Elzenga (May 13, 2019)

There is another problem and I think that is what happens to the OP. Standard-sized previews are generated taking the resolution of the monitor into account. They _should_ be generated with the hardware resolution as guide, so on a 5K iMac the standard-sized previews should be 5K. That means they should be 5120 wide if you set the preview resolution in the catalog settings to 'Auto'. There is a bug in Lightroom however where Lightroom does not use the true hardware resolution, but 2x the software resolution. It does so with the interface items, and that is correct behavior (a bit of a long story to explain why), but it also does that for previews and that is not correct.

The result is that (if you set the previews to 'Auto') the standard-sized previews are generated at a resolution that is depending on your monitor settings. So if you set your monitor to 'More space' (which could be 3200 x 1800 pixels, for example), then Lightroom wants to generate 6400 pixels wide standard-sized previews. That is even bigger than 1:1 previews for a lot of cameras... What you can do is set the resolution to a fixed setting instead of Auto. I've set mine to 2880 pixels (on a 4K screen) and they look fine.


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## gYab61zH (May 13, 2019)

Ferguson said:


> What kind of monitor do you have, if I might ask, that is 6000 on a side?


Sorry, I thought I had mentioned that sufficiently in my original post. I have a 5K iMac (27"), which has 5120 x 2880, and LR CC defaults to 5120 in its auto setting.


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## Johan Elzenga (May 13, 2019)

gYab61zH said:


> Sorry, I thought I had mentioned that sufficiently in my original post. I have a 5K iMac (27"), which has 5120 x 2880, and LR CC defaults to 5120 in its auto setting.


Then there is no problem. Generating 1:1 previews is not useful, because these are generated on top of the standard sized previews, not instead of them. You could try to set the size to 2880 pixels however, and see if that really makes a big difference.


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## gYab61zH (May 16, 2019)

Thanks for all the info. What happens when I set 1:1 on import instead of standard? Surely, LR does not then generate standard previews as well? And when I say "never" to the delete option, does that mean they stay and are only deleted/updated when I edit a file, or do I need to generate them manually again?

PS. I do not mind generating new previews for all my files every now and then (even if it takes a few days) since I find it to be a great diagnostic tool in that a failed preview signals there is something wrong with one of the files.


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## Johan Elzenga (May 16, 2019)

gYab61zH said:


> What happens when I set 1:1 on import instead of standard? Surely, LR does not then generate standard previews as well?


It does generate them as well. The previews are actually a pyramid of previews in different sizes, up to standard-size. Only 1:1 previews are extra. They are either generated when needed (when you zoom in), or because you set that option during import. But they are not generated instead of the other previews.


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## gYab61zH (May 17, 2019)

Ah ... but how do you explain the fact that my "catalogue Previews.lrdata" has barely grown after I generated 1:1 previews for about 100000 images?


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## Johan Elzenga (May 17, 2019)

gYab61zH said:


> Ah ... but how do you explain the fact that my "catalogue Previews.lrdata" has barely grown after I generated 1:1 previews for about 100000 images?


I believe I already explained that. Your standard-size previews are as big as 1:1 previews, because of your screen resolution.


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## gYab61zH (May 19, 2019)

I am still confused and obviously not getting it. What you said Johan was that "Only 1:1 previews are extra". If they are extra, i.e. on top of the pyramid of standard previews, and I generate 1:1 previews for all my images surely my "catalogue Previews.lrdata" should have grown quite dramatically, since the 1:1 previews are now added to the existing ones?


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## Johan Elzenga (May 20, 2019)

gYab61zH said:


> I am still confused and obviously not getting it. What you said Johan was that "Only 1:1 previews are extra". If they are extra, i.e. on top of the pyramid of standard previews, and I generate 1:1 previews for all my images surely my "catalogue Previews.lrdata" should have grown quite dramatically, since the 1:1 previews are now added to the existing ones?


Apparently Lightroom is clever enough not to duplicate previews. If your standard-sized preview is as big as a 1:1 preview would be, then generating an extra 1:1 preview does not make sense.


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## gYab61zH (May 20, 2019)

Apparently ... but the fact is that my max standard preview size is ever so slightly less than 1:1, and following your reasoning I would have to assume the program thinks that is close enough so as not to have to generate 1:1. Besides, when I did generate 1:1 it took forever, so it was clearly doing something. Could it be that 1:1 are not stored in "catalogue Previews.lrdata"?


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## Johan Elzenga (May 20, 2019)

No, it could not. They are stored in there. It’s possible that it worked the other way round and that Lightroom decided that the 1:1 preview would be close enough to replace the standard-size preview in this case. I simply don’t know.


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## gYab61zH (May 20, 2019)

Thanks for you help.


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