Explanation for SIZE of Previews of 40GB in LrC ?

[giancatt.stmoritz]

l work with Lightroom since more then 10 years and have accumulated many pictures as a professional press photographer. I work with Photoshop since 20 years.

in my LrC are 370'000 images at the moment, mostly RAW files. few JPG files kept from the early days.

l have a MacPro late 2013 with 64 GB RAM !!!

catalina, 3 units of DROBO 5D with lots of Harddisk space.

I do backups every day.

on the Drobo Master there are of course many more images which are not or not anymore in the LrC catalog.

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when starting LrC on my MacPro I can see like in the actual screenshot 19.2 GB RAm available

after editing images the RAM starts getting RED Color and LrC is slowing down.
i close all apps I don't need.

at some point l close LrC and restart it again to free up RAM.

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screenshot no 2 shows the Previes size is 40GB !!! FORTY !

so l think this is way to much.

but l have no idea how to reduce the PREVIEW SIZE.

>>> any idea to have LrC make smaller previews ?

l have tried a few setting but .... mmmhhhh no change.

hopefully some of you out there comes up with something ?

thanks in advance and

ciao

[johnrellis]

"in my LrC are 370'000 images ... screenshot no 2 shows the Previes size is 40GB"

That's normal and represents less than 2% of the total disk space used for your images.

With previews using 40.15 GB for 370,000 images, that's about 109 KB per image. (Previews for my catalog of 33,633 images take about 718 KB per image.) If your press images are mostly JPEGs of, say, 5 MB each, then 109 KB per preview represents about a 2% overhead for preveiws.

[giancatt.stmoritz]

...If your press images are mostly JPEGs of, say, 5 MB each...

mostly RAW Nikon files NEF of professional cameras.

where can I see how large in k is a preview ?

thank you !

[johnrellis]

"mostly RAW mostly RAW Nikon files NEF of professional cameras."

So the disk overhead of the previews is even smaller, less than 0.5%.

"where can I see how large in k is a preview"

It's difficult to see the size of any one preview. But it's easy to calculate the average size: 40.15 GB / 370,000 images.

[ManiacJoe]

As John points out, things are working normally.

Since the preview folders are a cache system, if you need the space back, you can delete the preview folder while LR is NOT running, and the cache will be rebuilt as needed starting off at a much lower size.

Alternatively, you can transfer the catalog and its supporting subfolders to a different internal or external (not network) drive.

[giancatt.stmoritz]

..  if you need the space back, you can delete the preview folder while LR is NOT running...

interesting. l have to try this.

thank you

[Jao vdL]

If you do so, you'll open up to a Lightroom interface with grey previews hat will slowly be recreated. Typically the database will grow over time to about the same size as before. Doing this really only makes sense if the size is outrageous which 40 GB isn't.

[Jao vdL]

Only 40GB for 300k images is extremely small. You must have only tiny previews set up as standard or you're working on a low resolution display. I have 100k images and my previews are 140 GB. That is about the size I would expect for the size of my display.

[giancatt.stmoritz]

.... you're working on a low resolution display. ...

no l have an Apple LED Cinema Display 

see screenshot

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...Only 40GB for 300k images is extremely small.

but the 40GB fill up my RAM ? or not ?

thank you

[Jao vdL]

Ah. Yeah the cinema display is considered low resolution nowadays. I am working on a retina Mac Book Pro with a 4k monitor which necessitates much larger previews. The preview database does not take up space in your RAM. It just takes up space on your hard drive. They are there to speed up display of your images when browsing. 

[giancatt.stmoritz]

.... The preview database does not take up space in your RAM. It just takes up space on your hard drive. They are there to speed up display of your images when browsing. ...

ohhh ... ok so l can feel better now. thank you.

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what do you think about filling up my 64GB  while working with LrC ? 

anyhow thanks a lot for your information. great.

[Jao vdL]

Well-designed programs should be using as much RAM as they can so it filling up is normal. However if it makes your whole computer slow down it is not well behaved. Lightroom has always had some memory leak issues that led to in certain cases, especially computers with lots of RAM and lots of computing power to have memory leaks where it won't give up memory when needed by other parts of the system. Not everybody has this problem but if you search this forum you'll find that lots of people complain about slow downs of the program during use to the point that it can even become unresponsive until you quit and restart it. I have never seen such behavior on my Mac Book Pro 6-core i9 with 32 GB of memory and I basically never quit Classic and it will run just fine for months even but others can't run for more than an hour before getting into quagmire land. Many of these bugs have been fixed over the years so it makes sense to ensure you are at the very latest Classic (v 10.2)