Size matters.

This time, I mean size of files. A student just wrote to ask:


“I have taken photos for some friends and used Lightroom for editing and exporting.  I did not shoot in RAW- still learning.  My SOOC images are substantially larger than my exported JPEG files.  For instance, one file is 6.72 MB but comes out 800KB once run through Lightroom.  I am exporting at a quality of 80, length and width of 4×6 and resolution of 300ppi.  My friend has asked me for larger files.  I am under the impression that larger files don’t necessarily mean better images, but perhaps I am wrong? Is this downsizing normal? I have never had any issues with print quality as long as I size in a 4×6 inch ratio and set 300ppi as my resolution.  Am I doing something wrong in exporting that is causing such a dramatic drop in file size?”


This is perfectly normal. A 7MB JPG (or a 14 MB RAW) will indeed be about 800 kB at those settings. Yes, your new JPG is smaller:

  • 300 ppi x 6″ = 1800 pixels wide, which is about one quarter of the actual size of the file.
  • 80% is going to result in a much smaller size than 100%: compression is the entire point of JPG files.

So if the original file is 6MB, then a quarter of that is 1.5MB, and with extra compression, 800 kB seems a perfectly normal file size: as expected.

Indeed, a larger file means better image quality. This is always the case; whether it is noticeably better is another question, of course.

I tend to think in pixels, Saying “1200 pixels long” is easier than saying “4 inches at 300 ppi”, and it means the same. You can specify either way, but I always prefer the simplest.

Finally: you tell me you are shooting a wedding soon. You should be shooting RAW. What is there to learn? Just select RAW as the filetype instead of JPG. Done. If you use Lightroom to finish your pictures, it will know the RAW format your camera produces: done. Simple.

And yes, sometimes things that appear simple are simple.


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