Exporting file size question

[Takeone.Digital]

Hi to all,
my system- WIN10 with LR clasic updated (12.4) 16 GB RAM.
The camera (Sony A7C) is configured for RAW + JPEG in each image shooting.
The RAW file size before processing in LR is about ~ 40 MB in resolution of 4000 x 6000.
I export to JPEG in LR at the same resolution and sometimes get a file with a size of only 4 MB.
I don't see a problem with the image- just wonder if there is a lot of "lost information" effecting the final quality.
The export settings> unchanged resolution, 300 pixels per inch, quality 100.
Is this normal or something that needs further checking in the LR settings?

Attached - 4 MB Jpeg processed from a 46 MB RAW.

[dj_paige]

JPG is a compression technology — the idea is to compress the image so that the file takes up less space, without any (noticeable) loss of quality. So what you are seeing is perfectly normal.

I would reduce the Image Quality setting to 70 or 80, the files will get much smaller without any (noticeable) loss of quality.

[richardplondon]

A given Raw is capable of being processed into many different looking treatments, so perhaps you can think of it as containing a less decided but also a fuller set of information, than is the case for a JPG that is dedicated to displaying a particular edited treatment (and only that). But the way your photo exists as a Raw, and the way it gets exported as a JPG, are so different both in principle and in practice: that the two file sizes can't IMO be compared directly with any meaning.

On the other hand, if an image is sent to e.g. Photoshop for external editing, it gets saved into a format that is almost always larger than, and sometimes massively larger than, the Raw that was its original source. SO your 46MB Raw might be exported to just a few MB. If you moderate the saving quality down to say 80, that is IMO ample, also it may be that a lower pixel resolution (resizing) suits your requirement perfectly well and that makes an even bigger difference. But a Photoshop working file could be 200MB easily, and many times that size is commonplace.

In those terms, also considering that one unchanged Raw can underlie many differing virtual editing treatments within a Catalog. Raw can even be considered quite space efficient. One reason is that typically, each "pixel location" within the Raw is represented by just one number - rather than by 3 separate numbers denoting the Red, Green and Blue components of the colour for that pixel.

[Per Berntsen]

The image contains large smooth, out of focus areas, that compress well, which explains the relatively small file size. If there had been sharp, busy detail in most of the image, which doesn't compress well, the file size would have been much larger. Image content has a huge influence on the file size of a jpg.

This slightly ovesharpened image was exported (full size, 85 quality) from a 7.1 MB raw file, and the file size is 4.5 MB.

Below is the same image with no sharpening, and painted with a brush with Sharpness and Texture set to -100. Exported with the same settings as the first image. The file size is 975 KB.

[Takeone.Digital]

thank you all.

I think the 3 you've made points is clear now.