File size after export in Lr CC

[Fruitmn]

I have just started using LR and have just notices that my file sizes are small after I exported out of LR. 

For example, I have a picture that I took in RAW and it is 24.8MB on my CF card.  I have done no editing of the picture and just exported it to a file on my desktop and it went from 24.8MB to 10.5MB.  the dimensions stayed the same at 5472 × 3648.  I plan on making these into large prints. ( 24x36" or larger)  Is this going to be an issue?

Thanks a million

Canon 1DX mk ii 70-200 2.8 L IS 2

Canon 7D mk ii 24-70 2.8 L IS 2

[DdeGannes]

You have probably exported the file to Jpeg. format which is 8 bit file and compressed. So its not the full resolution.

There is also the option to export as a t.ff file 8 bit or 16 bit.

16 bit is the full l resolution and will be even larger than the raw file.

[Fruitmn]

OK, I use to use Photoshop Essentials 14 for the same work and It didn't shrink the MB like it does in LR.  And I need the pics to be in JPEG so other people can see them on their phones and computers.  So is there anything I can do to change the settings or am i just out of luck.

[JP Hess]

That is a pretty normal reduction in file size when going from a raw image to a JPEG. Did you set the quality to 100? If those dimensions are the same dimensions as the raw file in Lightroom then you do have a full resolution image. To print an image as large as you are wanting it will probably have a resolution of about 150 PPI. That should be sufficient for an image that size because you won't be standing with your nose against the picture. What are the dimensions of the raw file in Lightroom?

[Fruitmn]

The ORIGINAL RAW dimensions are 5472 x 3648 @ 24.8MB

The unedited JPEG dimensions are 5472 x 3648 @ 10.5 MB after export from LR into a file on my desktop

[ManiacJoe]

Those numbers sound reasonable.

Your raw file is 14-bit color or bigger, the JPG is 8-bit, so the max size of the JPG will be about half the size of the raw file.

JPG files use a lossy compression, so the files will be even smaller than half. 90% is an excellent compression setting.

The size of the file is not important for image quality.

The number of pixels (5472 x 3648) is what is important.

DPI/PPI is meaningless for anything other than printing, and even then it is the first number to be discarded and recalculated.

[Rob_Cullen]

Jeffrey Friedl has a great visual guide to image JPG compression and resulting file size at-

Jeffrey Friedl's Blog » Lightroom JPEG Export-Quality Settings, Full-Resolution Examples

Also a nice explanation by Laura Shoe here-

JPEG Compression and the Lightroom JPEG Quality Setting | Laura Shoe's Lightroom Training, Tutorials...