# Question about previews sizes



## JimHess43 (Sep 20, 2012)

I need some clarification about preview sizes.  I have been creating 1:1 previews routinely in Lightroom.  I understand the difference in quality.  But, I'm still using a 32 bit computer and not quite ready to upgrade yet.  I know, there's a big difference.  And I experience that difference because I have a 64 bit computer at work.  If I do a small, experimental shoot (20 images) my 32 bit computer can take as long as 5 minutes to generate 1:1 previews for that set of imported images.  If I choose to generate minimal previews that waiting time is virtually nonexistent.  My question is: when I open one of those images in the Develop module does Lightroom generate a 1:1 preview?  If it does then I'm willing to wait for the second or two that it takes to generate that preview.  In other words, can I import generating minimal previews and still get accurate results in the Develop module?  Maybe it's my aging eyes, but with my experimenting last night it seemed to be OK.


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## Jim Wilde (Sep 20, 2012)

Jim, the previews that you render on import, or using the Library>Previews option, are not what you see in Develop. The latter renders anew every time you open a file (unless cached within the same session), using the original file plus any partly-demosaiced data which is stored in the ACR cache. As such the 1:1 previews which you choose to render are really only useful if you typically view images at 1:1 resolution in Library.

So purely in terms of the Develop module, it makes little difference what size of preview you have rendered during Import or in Library.


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## JimHess43 (Sep 20, 2012)

Thank you for your reply.  That is exactly what I wanted to know.  That little discovery last night removed a big bottleneck from my workflow.


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## trevorb (Sep 21, 2012)

Thanks from me as well. It was onmy list of questions.


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## Tony Jay (Sep 21, 2012)

Depending on how you use Lightroom, 1:1 previews also allow one the facility of using them in the Slideshow module WITHOUT your high-resolution originals.
The utility of this is that your ENTIRE catalog can be loaded on a laptop - such as when you travel - without your valuable original files.
As mentioned earlier they are also of value in the Library module.

Particularly if you are a pro who needs to travel frequently, need access to your catalog, but don't want to risk your high-resolution originals this is an ideal workaround since the previews are stored with the catalog.

Regards

Tony Jay


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