Oct 182011
 

Anytime you create a jpeg using Lightroom’s Export dialog (or any other method), the file is compressed — information is thrown away in order to make the file smaller. How much is determined by the Quality setting or, in Lightroom 3 or later, if you choose instead, the Limit File Size setting.

The big benefit of jpeg files is that they are relatively small.  The jpeg save algorithm is complicated, but it basically evaluates each pixel in your image, looking at pixels surrounding it to see if they are “close enough” in color and tone. If they are “close enough”, then they are changed to be  the same. This way the file doesn’t need to store as many pieces of information and can be smaller. How close is “close enough” is determined by the Quality setting, which ranges from 0 to 100.

lightroom export jpeg quality setting

Lightroom Export Dialog Jpeg Settings

Here is an email-sized photo (approximately 400×600 pixels) saved at Quality=100:

Lightroom jpeg export at quality 100

And here is the same photo, saved at Quality=0:

lightroom export jpeg quality 0

Here is a close-up comparison (zoomed in to 4:1 / 400%, so you are seeing individual pixels in both):

comparison of lightroom jpeg quality 0 to 100

Quality=0 Compared to Quality=100

In this case, the Quality=100 file is 298 kb, and the Quality=0 file is 79 kb.  The file savings with each image will be different, based on the amount of detail in the image. 

Note that even at Quality=100, information is being thrown away, but you would be hard-pressed to see any difference from your original or an uncompressed tiff file.  With this image, the tiff would be 665 kb, so going with a jpeg at Quality=100 more than cuts the file size in half, with no visible loss in quality.

When I am emailing an image or putting it on the web, my goal is usually to get the smallest file possible, without visually degrading the image.  I find that a quality setting of 60-70 is sufficient.  For this image, Quality=65 reduces the file size to 135 kb, and the image looks fine:

lightroom-export-jpeg-quality-65

If I zoom into 4:1 I can see some subtle differences, such as in the roof of the car, but they are not visible at 1:1, which is what I care about.

comparison-of-lightroom-jpeg-quality-65-to-100

Quality=65 Compared to Quality=100

Unfortunately Lightroom’s export dialog doesn’t give you a preview of the result, so the only way to experiment is to do exports at various settings.  You will find that higher quality settings are required for images with smooth areas with subtle transitions in color and tone, such as with skies, faces, and this car.

If I am sending an image out to print and the printer wants a jpeg rather than a tiff (which is not compressed, and is therefore much bigger), then image quality becomes more important than file size to me.  I will set quality at or close to 100.  The file will be bigger, but it will be uploaded online or delivered in-person rather than emailed.

In Lightroom 3, the Limit File Size option was introduced as an alternative to using the Quality setting.  Because each image is different, you can’t predict how big the file will be at any given Quality setting.  The Limit File Size option is designed to overcome this.  You can specify that the file must not exceed, say 500 kb, and Lightroom will use the highest quality setting possible that achieves that goal.  I find this to be very handy when quality is really important to me but I need to put a cap on file size for whatever reason.

Experiment with the settings using your own images!  On a Mac you can see how big the resulting jpegs are by right-clicking on them (Ctl-click with a one button mouse) in Finder and choosing Get Info.  On a PC you can right-click on them in Windows Explorer/My Computer and choose Properties.

Note that jpeg compression is the second major difference between shooting raw files versus shooting jpegs.  You can fit more jpegs on your memory card because they are much smaller, but you will have lost information.  If you choose the “large jpeg fine” settings in-camera, you may never notice the difference, but why give up information when you don’t have to?

 

 

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  10 Responses to “Jpeg Compression and the Lightroom Jpeg Quality Setting”

  1. I agree, it would be nice if Lightroom could give us a little more help on this problem.

    In the meantime. Jeffrey Friedl has an interesting Lightroom plugin, the “JPEG Export Quality Tester”.

    The plugin generates jpegs at all of Adobe’s quality levels so you can compare their sizes and visual characteristics for suitability. Nice tool.

  2. Perhaps also of interest: interactive examples on my “An Analysis of Lightroom JPEG Export Quality Settings” writeup, which is the background discussion to the quality-tester plugin that Doug mentions. (Thanks for the shoutout, Doug).

  3. Er, I seem to have broken the link in my previous comment. The link should be:

    http://regex.info/blog/lightroom-goodies/jpeg-quality

    • Jeffrey,

      When I discoverd your article many moons ago it was a huge time and space saver. Every Lightroom user should be required to read your article.

  4. At one time I always used to save jpegs at the 100% setting ‘just to be sure’. The files were huge and cumbersome to copy or upload. Then I read Jeffrey Friedls’ article (referenced above) which is an excellent piece of work. I now use a quality setting of 75% as a general rule which gives a greatly reduced file size which is quite manageable, and I have not found any significant loss of quality on any file at that setting, even when viewed at 4:1

    Laura has independently given much the same advice in another excellent article. Its good advice too I recommend anyone to read both Laura and Jeffreys articles and heed their advice.

  5. [...] my tutorial on jpeg quality, I displayed two photos side by side and zoomed in on them together to compare them up close. A [...]

  6. What could I be doing wrong when my exported photos show a noticeable difference in colour tones and quality, even when exporting as uncompressed 16bit TIFF. When I look at the photo in Lightroom and then the exported TIFF or JPG file in windows preview, there’s obvious changes. I shoot mostly night photography, could the ‘extreme’ environment of colour values have something to do with it – like one portrait is an eight second exposure with the red dashboard light as the only source. That red gets exported as deeper and darker, and whereas the pupil in lightroom is small, the colour seems to disappear in the exporting, making the total eye areas look like dilated pupils.

    • Sorry for the delay, Gordon, but it is a color space issue. Lightroom works in Prophoto, which is a very large color space. When you export, you specify the color space to be exported to, and need to choose something that will be compatible with where/how the photos will be displayed. For example, for web sharing and all but pro-level printing, sRGB is appropriate – and this is smaller than ProPhoto, so really richly saturated colors will be modified.

      I discuss color spaces in depth in my Producing Great Output video series.

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