Smart preview dng file exceeding 500 mo size

[peyreoli]

Dear reader, 

I'm seeing in my smart previews folder/package some dng files having exceptional huge size, around 500 mo!!! That gives to the total SP package a size of 200Go 😞 They are smart previews from jpg pictures. Some might be coming from corrupted pictures (one does at least). Most of my other dng files in the smart previews package do not exceed 2 or 3 mo. I  have nearly onnly jpg files and no RAW pictures in my catalog.  

Anyone having the same problem?   Any solution about this to reduce the SP package? 

Thanks

[JP Hess]

What is the size issue with this smart preview package? 

[peyreoli]

Thanks for your interest in my pb.

answer is : a dng file of 500mo!!! for a smart preview that is supposed to reduce size of tho original file ....  and the original file being a jpg file of about 5Mo... That is something I consider as a bug, shouldn't I? Where am I having it wrong? Do you think it s a normal size?

[dj_paige]

In Lightroom, you can delete selected (or all) smart previews, but you can't really change the size of an individual smart preview file.

Select the desired photos and then Library->Previews->Discard Smart Previews...

[peyreoli]

thank you i knew about this feature. I just wonder WHY these dng files are so big (500mo!!!)

[GoldingD]

Why would the OP be seeing DNG files in the SmartPreviews folder?

[dj_paige]

Maybe this is a language translation problem or a typo, but I don't know what "500 mo" is.

Specifically, I don't know what "mo" is.

[JohanElzenga]

o = b

[boomstam]

Hi all,

I am researching whether or not it is possible to use smart previews for non-raw pictures as well. There is little information on this, since the smart previews shine on RAW. My catalog consists mostly of RAW images but there are also a substantial number of JPG's and a fair few very large PSD and TIFF's.

What happens with the non-RAW images, are they being processed to DNG as well?  From Peyreoli's posting and kind answers below it seems possible for JPG at least. Love to hear other people's experience on this topic and find out about any considerations to make prior to applying smart-previews to a 75k images catalog 🙂

[peyreoli]

hello, all my catalog is jpg FYI. 400k images+shorts videos. a large parts
have smartpreviews dng format. So it works . But with the problem I have
described before. sometime one dng get to become a 500mb file instead of 1
to 5mb as usual...

[JohanElzenga]

Lightroom can generate smart previews for all the image formats it supports. You do not get any special advantages however. A smart preview generated from a jpeg image will have the same limitations (compared to raw) as the jpeg original has.

[boomstam]

Hi all,

Thanks for getting back. The reason for switching to smart previews is performance. My pics are on a 2T raid 1 NAS. In itself this works but it is slow. I would think that using smart previews on a super fast SSD disk using Thunderbolt 3 to my Mac Mini Most would be beneficial to get more speed during LR operations, as most of my pics are NEF (RAW). Of course the originals would still reside on the NAS.

[JohanElzenga]

It will, but make sure you check this box (otherwise it won't):

[Jao vdL]

You really do not want to make smart previews for jpegs. It will not give any speed advantage, and quality will be limited. Only exception is if the jpegs are gigantic files so the scaling down to 2560 pixels on the long edge will resolut in a much smaller image. Think stitched panoramas for example. Still even then the utility of doing this is very questionable. Also as Johan shows, to get any advantage out of smart previews, you have to enable them for editing. They are not by default and only get used when you don't have the original available. 

I have never seen the point of smart previews if you are not doing any offline editing. The promised speed up is very questionable and negated by the need to first generate them which is a slow process. They are great for offline editing and sending quick mock-ups around though.

[JohanElzenga]

It will also depend on the computer. An older laptop will benefit perhaps, while a modern desktop may not show any improvement. For the OP, which originals on a NAS, it may work too. The option to use smart previews to speed up processing was introduced by Adobe as a reaction to tutorials where people advised to generate smart previews and then deliberately disconnect the originals, either by disconnecting the external drive, or by temporarily renaming the originals folder on the internal drive. So apparently some people found it worked well enough for them to go through that hassle. I agree that is very unlikely that it works for jpegs, except for massive ones. It was advised for raw files, and probably mainly raw files from high megapixel cameras.

[peyreoli]

Hello and thanks for all your comments so far. But the question of why do I have dng files of 500mb each has not been really answered. Any idea maybe?